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May 27, 2008, 3:28:48 PM5/27/08
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NEVER MIND SCHOLARSHIPS; GET HIM AN INVESTOR
http://en.wikipedia.org/wiki/Pseudomonas
http://en.wikipedia.org/wiki/Sphingomonas
CANADIAN TEEN DECOMPOSES PLASTIC BAG IN THREE MONTHS
http://blog.wired.com/wiredscience/2008/05/teen-decomposes.html
By Brandon Keim / May 23, 2008
"The Waterloo, Ontario high school junior figured that something must
make plastic degrade, even if it does take millennia, and that
something was probably bacteria. (Hey, at between one-half and 90
percent of Earth's biomass, bacteria's a pretty safe bet for any
biological mystery.)
The Record reports that Burd mixed landfill dirt with yeast and tap
water, then added ground plastic and let it stew. The plastic indeed
decomposed more quickly than it would in nature; after experimenting
with different temperatures and configurations, Burd isolated the
microbial munchers. One came from the bacterial genus Pseudomonas, and
the other from the genus Sphingomonas.
Burd says this should be easy on an industrial scale: all that's
needed is a fermenter, a growth medium and plastic, and the bacteria
themselves provide most of the energy by producing heat as they eat.
The only waste is water and a bit of carbon dioxide. Amazing stuff.
I'll try to get an interview with this young man who may have managed
to solve one of the most intractable environmental dilemmas of our
time.
And I can't help but wonder whether his high school already had its
prom. If he doesn't get to be king, there's no justice in this world."
AGREED: DANIEL BURD FOR PROM KING
http://apps.ysf-fsj.ca/virtualcwsf/projectdetails.php?id=1390
"My name is Daniel Burd, a grade 11 student at Waterloo Collegiate
Institute. I performed my first “science” experiment involving
planting and observing growth of different types of tomato seeds on
the balcony of our apartment in Waterloo eleven years ago. Since that
time, the ideas and concepts behind the way things work have
constantly aroused my interest and have posed numerous questions for
me to consider. At school, I am on ABCD Student Council, Charity
Controller, Environment club, a peer tutor, and Norse Star newspaper.
When I was five years old, I started to play the piano and I have
completed my grade 8 piano and grade 2 rudiments at the RCM.
Currently, I am learning improvisation and jazz. My jazz music role
model is Oscar Peterson. I am a member of Nordic Skiing club, ROW
swimming club and Waterloo Tennis Club where I am training for
tournaments. I am a volunteer at K-W Science and Technology Children’s
Museum. I help organize heritage events in K-W area and I run a
charity dog-walking business in my neighborhood for people with
disabilities. I fluently speak English, French and Russian and I enjoy
spending free time with my friends."
Awards
- The Manning Innovation Achievement Award - $500.00
- Dalhousie University Faculty of Science Entrance Scholarship
Senior Gold Medallist - $4000 Entrance Scholarship
- NSERC Undergraduate Student Research Award
Senior Gold Medallist - $5 625.00
- UBC Science (Vancouver) Entrance Award
Senior Gold Medallist - $4000 Entrance Scholarship
- University of Ottawa Entrance Scholarship
Senior Gold Medallist - $20,000 Entrance Scholarship
($5,000 each year for 4
years)
- Senior Silver Medallist - $3000 Entrance Scholarship
- The University of Western Ontario Scholarship
Gold Medallist - $2000 Entrance Scholarship
- The University of Western Ontario Scholarship
Silver Medallist - $1500 Entrance Scholarship
- Silver Medal - Environmental Innovation - $700.00
- Gold Medal - Biotechnology & Pharmaceutical Sciences - $1 500.00
- EnCana Platinum Award - Best Senior Project - $5 000.00
- EnCana Best in Fair Award - $10 000.00
Total $57 825.00
YEAST, TAP WATER, DIRT
http://news.therecord.com/article/354044
WCI student isolates microbe that lunches on plastic bags
BY Karen Kawawada
Getting ordinary plastic bags to rot away like banana peels would be
an environmental dream come true. After all, we produce 500 billion a
year worldwide and they take up to 1,000 years to decompose. They take
up space in landfills, litter our streets and parks, pollute the
oceans and kill the animals that eat them. Now a Waterloo teenager has
found a way to make plastic bags degrade faster -- in three months, he
figures.
Daniel Burd's project won the top prize at the Canada-Wide Science
Fair in Ottawa. He came back with a long list of awards, including a
$10,000 prize, a $20,000 scholarship, and recognition that he has
found a practical way to help the environment. Daniel, a 16-year-old
Grade 11 student at Waterloo Collegiate Institute, got the idea for
his project from everyday life. "Almost every week I have to do chores
and when I open the closet door, I have this avalanche of plastic bags
falling on top of me," he said. "One day, I got tired of it and I
wanted to know what other people are doing with these plastic bags."
The answer: not much. So he decided to do something himself. He knew
plastic does eventually degrade, and figured microorganisms must be
behind it. His goal was to isolate the microorganisms that can break
down plastic -- not an easy task because they don't exist in high
numbers in nature.
First, he ground plastic bags into a powder. Next, he used ordinary
household chemicals, yeast and tap water to create a solution that
would encourage microbe growth. To that, he added the plastic powder
and dirt. Then the solution sat in a shaker at 30 degrees. After three
months of upping the concentration of plastic-eating microbes, Burd
filtered out the remaining plastic powder and put his bacterial
culture into three flasks with strips of plastic cut from grocery
bags. As a control, he also added plastic to flasks containing boiled
and therefore dead bacterial culture.
Six weeks later, he weighed the strips of plastic. The control strips
were the same. But the ones that had been in the live bacterial
culture weighed an average of 17 per cent less. That wasn't good
enough for Burd. To identify the bacteria in his culture, he let them
grow on agar plates and found he had four types of microbes. He tested
those on more plastic strips and found only the second was capable of
significant plastic degradation.
Next, Burd tried mixing his most effective strain with the others. He
found strains one and two together produced a 32 per cent weight loss
in his plastic strips. His theory is strain one helps strain two
reproduce. Tests to identify the strains found strain two was
Sphingomonas bacteria and the helper was Pseudomonas. A researcher in
Ireland has found Pseudomonas is capable of degrading polystyrene, but
as far as Burd and his teacher Mark Menhennet know -- and they've
looked -- Burd's research on polyethelene plastic bags is a first.
Next, Burd tested his strains' effectiveness at different
temperatures, concentrations and with the addition of sodium acetate
as a ready source of carbon to help bacteria grow. At 37 degrees and
optimal bacterial concentration, with a bit of sodium acetate thrown
in, Burd achieved 43 per cent degradation within six weeks.
The plastic he fished out then was visibly clearer and more brittle,
and Burd guesses after six more weeks, it would be gone. He hasn't
tried that yet. To see if his process would work on a larger scale, he
tried it with five or six whole bags in a bucket with the bacterial
culture. That worked too. Industrial application should be easy, said
Burd. "All you need is a fermenter . . . your growth medium, your
microbes and your plastic bags." The inputs are cheap, maintaining the
required temperature takes little energy because microbes produce heat
as they work, and the only outputs are water and tiny levels of carbon
dioxide -- each microbe produces only 0.01 per cent of its own
infinitesimal weight in carbon dioxide, said Burd. "This is a huge,
huge step forward . . . We're using nature to solve a man-made
problem."
Burd would like to take his project further and see it be used. He
plans to study science at university, but in the meantime he's busy
with things such as student council, sports and music. "Dan is
definitely a talented student all around and is poised to be a leading
scientist in our community," said Menhennet, who led the school's
science fair team but says he only helped Burd with paperwork.
PEDIGREE
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=CTP_003309&use_sec=true&sec_url_var=region1
Microbes convert ‘Styrofoam™’ into biodegradable plastic /
02/23/2006
"Bacteria could help transform a key component of disposable cups,
plates and utensils into a useful eco-friendly plastic, significantly
reducing the environmental impact of this ubiquitous, but difficult-to-
recycle waste stream, according to a study scheduled to appear in the
April 1 issue of the American Chemical Society journal, Environmental
Science & Technology.
The microbes, a special strain of the soil bacterium Pseudomonas
putida, converted polystyrene foam — commonly known as Styrofoam™ —
into a biodegradable plastic, according to Kevin O’Connor, Ph.D., of
University College Dublin, the study’s corresponding author. The study
is among the first to investigate the possibility of converting a
petroleum-based plastic waste into a reusable biodegradable form.
O’Connor and his colleagues from Ireland and Germany, utilized
pyrolysis, a process that transforms materials by heating them in the
absence of oxygen, to convert polystyrene — the key component of many
disposable products — into styrene oil. The researchers then supplied
this oil to P. putida, a bacterium that can feed on styrene, which
converted the oil into a biodegradable plastic known as PHA
(polyhydroxyalkanoates). The process might also be used to convert
other types of discarded plastics into PHA, according to O’Connor.
PHA has numerous uses in medicine and can be used to make plastic
kitchenware, packaging film and other disposable items. The
biodegradable plastic is resistant to hot liquids, greases and oils,
and can have a long shelf life. But unlike polystyrene, it readily
breaks down in soil, water, septic systems and backyard composts.
Worldwide, more than 14 million metric tons of polystyrene are
produced annually, according to the U.S. Environmental Protection
Agency. Most of this ends up in landfills. Although polystyrene
represents less than 1 percent of solid waste generated in the United
States, at least 2.3 million tons of it is dumped in U.S. landfills
each year. Only 1 percent of polystyrene waste is currently recycled,
the authors note."
CONTACT
Kevin O' Connor, Ph.D.
www.ucd.ie/biocatal
e-mail: kevin....@ucd.ie
SEE ALSO
Anthony J. Sinskey, Sc.D.
http://web.mit.edu/biology/www/facultyareas/facresearch/sinskey.html
http://hst.mit.edu/public/people/faculty/facultyBiosketch.jsp?key=Sinskey
e-mail : asin...@mit.edu
Oliver Peoples, Ph.D. / Founder / Chief Scientific Officer, Metabolix
http://metabolix.com/
http://www.metabolix.com/natures%20plastic/coretechnology.html
http://www.metabolix.com/biotechnology%20foundation/biotechnologyfoundation.html
http://www.metabolix.com/sustainable%20solutions/sustainablesolutions.html
http://metabolix.com/resources/researchlinks.html
e-mail : peo...@metabolix.com
BIOPLAST
http://www.bioplast.com.tr/bioplast.html
http://www.bioplast.com.tr/bio-bozunur-plastics.html
PREVIOUSLY ON SPECTRE --- BIODEGRADABLE PLASTICS
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/a806584fe743400a/84334f2f76d7a48c?lnk=gst&q=PLASTIC#84334f2f76d7a48c
DOMESTICATING BIOTECH
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/10b613466cdccd56/10dd98161e8247ec?lnk=gst&q=BACTERIA#10dd98161e8247ec
GROW YOUR OWN BACTERIAL SLAVE ARMY --- SEA MONKEYS DONE FOR GOOD
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/338c3693773e818e/e27e7fa967783c03?lnk=gst&q=BACTERIA#e27e7fa967783c03
.
PSEUDOMONAS GENOME DATABASE
http://www.pseudomonas.com/
.
ALSO CAUSES SNOWFLAKES
http://www.efluxmedia.com/news_Bacteria_The_Main_Ingredient_in_Snowflakes_Scientists_Say_14620.html
Bacteria – The Main Ingredient in Snowflakes, Scientists Say
BY Max Brenn / February 29th 2008
One might rethink playing with snow or walking in the rain as a new
study by scientists from the Louisiana State University revealed that
snow and rain might form mostly on bacteria in the clouds. Scientists
have long known that the ice crystals in clouds, which become rain or
snow, need to cling to some kind of particle, called ice nucleators,
in order to form in temperatures above minus 40 degrees Celsius.
Microbiologist Brent Christner at Louisiana State University sampled
snow from Antarctica, France, and the Yukon and found that as much as
85 percent of the nuclei were bacteria, he said in a telephone
interview with the Associated Press. “Every snow and ice sample we’ve
looked at, we found biological ice nucleators. Here’s a component that
has been completely ignored to date,” Christner said. The most common
bacteria found was Psedomonas syringae, which can cause disease in
several types of plants (tomatoes, green beams and other similar
plants). The bacterium was found in 20 samples of snow from around the
world and subsequent research has also found it in summer rainfall in
Louisiana.
Scientists have sought ways to eliminate this bacterium in time. Now
they wonder whether this elimination would result in less rain or
snow, or would soot and dust be the major generators of precipitation.
“The question is, are they a good guy or a bad guy. And I don’t have
the answer to that,” Christner said, quoted by the same source. One
thing is for sure. Bacteria that infect plants may multiply on the
plants’ leaves and drift into the atmosphere. These bacteria could
then cause precipitation and land on another plant, where the life
cycle could continue, Christner said.
Virginia K.Walker, a biologist at Queen’s University in Kingston,
Ontario, Canada said other studies have found bacteria serving as snow
nuclei, but this is the first to identify it as Pseudomonas. “It’s one
of those great bacteria…you can find them anywhere. They are really
interesting,” Walker said. The study, supported by a Louisiana State
University research grant and by the National Science Foundation and
the Earth Institute at Columbia University, was published in today’s
edition of the journal Science
CONTACT
Brent C. Christner
http://www.biology.lsu.edu/faculty_listings/fac_pages/bchristner.html
http://brent.xner.net/
email : xn...@lsu.edu
ABSTRACT
http://www.biology.lsu.edu/highlights/christner.html
Ubiquity of Biological Ice Nucleators in Snowfall
"Despite the integral role of ice nucleators (IN) in atmospheric
processes leading to precipitation, their sources and distributions
have not been well established. We examined IN in snowfall from mid-
and high-latitude locations and found that the most active were
biological in origin. Of the IN larger than 0.2 micrometer that were
active at temperatures warmer than -7°C, 69 to 100% were biological,
and a substantial fraction were bacteria. Our results indicate that
the biosphere is a source of highly active IN and suggest that these
biological particles may affect the precipitation cycle and/or their
own precipitation during atmospheric transport"
.
ONE BILLION PER QUART
http://www.time.com/time/magazine/article/0,9171,894282,00.html
Bugs in the Reactor / Oct. 05, 1959
Los Alamos' Omega West is a swimming-pool-type research reactor whose
fuel rods are suspended under 25 ft. of water, which acts not only as
coolant and moderator but also shields its human operators from
radioactivity. In the spring of 1958, physicists peering down through
it saw that the water was getting cloudy. They called Chemist-
Bacteriologist Eric B. Fowler of the laboratory's radioactive-waste
disposal group, who found that it was swarming with microorganisms,
about i billion per quart. The bugs turned out to be rod-shaped
bacteria of the genus Pseudomonas, which were feeding on resin and
felt in the water purifying system.
The fierce radiation in the reactor appeared to bother the bacteria
hardly at all. When the reactor was shut down but still highly
radioactive, they multiplied fast. Even when it was running full
blast, they held their own. Since they normally divide every 20
minutes or so, this meant that radiation was killing only about as
many as managed to live and divide. Just how much radiation the
Pseudomonas got is hard to estimate, because the water circulates at
varying distances from the core of the reactor, but Dr. Fowler thinks
they may have absorbed more than 10 million rep (roentgen equivalent
physical) in an eight-hour day, which is 10,000 times the dose that is
fatal to man.
Many other microorganisms must have got into Omega West's deadly
water; only the Pseudomonas survived. Perhaps the Pseudomonas have
natural resistance to radiation. More likely, under the bombardment of
Omega's radiation, normal Pseudomonas underwent mutation, producing a
special strain capable of surviving in this atomic blast. This ability
to transform themselves quickly to cope with new conditions is a
specialty of humble bacteria, whose constitutions are relatively
simple. It is an ability that higher animals cannot emulate, but may
have reason to envy.
.
PSEUDOMONAS AND YOU
http://www.horizonpress.com/pseudo
http://www.horizonpress.com/gateway/pseudomonas.html
The Taxonomy of Pseudomonas
The studies on the taxonomy of this complicated genus groped their way
in the dark while following the classical procedures developed for the
description and identification of the organisms involved in sanitary
bacteriology during the first decades of the twentieth century. This
situation sharply changed with the proposal to introduce as the
central criterion the similarities in the composition and sequences of
macromolecules components of the ribosomal RNA. The new methodology
clearly showed that the genus Pseudomonas, as classical defined,
consisted in fact of a conglomerate of genera that could clearly be
separated into five so-called rRNA homology groups. Moreover, the
taxonomic studies suggested an approach that might proved useful in
taxonomic studies of all other prokaryotic groups. A few decades after
the proposal of the new genus Pseudomonas by Migula in 1894, the
accumulation of species names assigned to the genus reached alarming
proportions. At the present moment, the number of species in the
current list has contracted more than ten-fold. In fact, this
approximated reduction may be even more dramatic if one considers that
the present list contains many new names, i.e., relatively few names
of the original list survived in the process. The new methodology and
the inclusion of approaches based on the studies of conservative
macromolecules other than rRNA components, constitutes an effective
prescription that helped to reduce Pseudomonas nomenclatural
hypertrophy to a manageable size.
Genome Diversity of Pseudomonas aeruginosa
The G+C rich Pseudomonas aeruginosa chromosome consists of a conserved
core and a variable accessory part. The core genomes of P. aeruginosa
strains are largely collinear, exhibit a low rate of sequence
polymorphism and contain few loci of high sequence diversity, notably
the pyoverdine locus, the flagellar regulon, pilA and the O-antigen
biosynthesis locus. Variable segments are scattered throughout the
genome of which about one third are immediately adjacent to tRNA or
tmRNA genes. The three known hot spots of genomic diversity are caused
by the integration of genomic islands of the pKLC102 / PAGI-2 family
into tRNALys or tRNAGly genes. The individual islands differ in their
repertoire of metabolic genes, but share a set of syntenic genes that
confer their horizontal spread to other clones and species.
Colonization of atypical disease habitats predisposes to deletions,
genome rearrangements and accumulation of loss-of-function mutations
in the P. aeruginosa chromosome. The P. aeruginosa population is
characterized by a few dominant clones widespread in disease and
environmental habitats. The genome is made up of clone-typical
segments in core and accessory genome and of blocks in the core genome
with unrestricted gene flow in the population.
Oligonucleotide Usage Signatures of the Pseudomonas putida KT2440
Genome
Di- to pentanucleotide usage and the list of the most abundant octa-
to tetradecanucleotides are useful measures of the bacterial genomic
signature. The Pseudomonas putida KT2440 chromosome is characterized
by strand symmetry and intra-strand parity of complementary
oligonucleotides. Each tetranucleotide occurs with similar frequency
on the two strands. Tetranucleotide usage is biased by G+C content and
physicochemical constraints such as base stacking energy, dinucleotide
propeller twist angle or trinucleotide bendability. The 105 regions
with atypical oligonucleotide composition can be differentiated by
their patterns of oligonucleotide usage into categories of
horizontally acquired gene islands, multidomain genes or ancient
regions such as genes for ribosomal proteins and RNAs. A species-
specific extragenic palindromic sequence is the most common repeat in
the genome that can be exploited for the typing of P. putida strains.
In the coding sequence of P. putida LLL is the most abundant
tripeptide.
Genetic Tools for Pseudomonas
Genetic tools are required to take full advantage of the wealth of
information generated by genome sequencing efforts, and ensuing global
gene and protein expression analyses. Although the development of
genetic tools has generally not kept up with the sequencing pace,
substantial progress has been made in this arena. PCR- and
recombination-based strategies allowed construction of whole genome
expression and transposon insertion libraries. Similar strategies
combined with improved transformation protocols facilitate high-
throughput construction of deletion alleles and development of a broad-
host-range mini-Tn7 chromosome integration system. While to date most
of these tools and methods have been developed for and applied in P.
aeruginosa, they will most likely also be applicable to other
Pseudomonas with appropriate modifications.
Molecular Biology of Cell-Surface Polysaccharides in Pseudomonas
aeruginosa: From Gene to Protein Function
Cell-surface polysaccharides play diverse roles in the bacterial
"lifestyle". They serve as a barrier between the cell wall and the
environment, mediate host-pathogen interactions, and form structural
components of biofilms. These polysaccharides are synthesized from
nucleotide-activated precursors and, in most cases, all the enzymes
necessary for biosynthesis, assembly and transport of the completed
polymer are encoded by genes organized in dedicated clusters within
the genome of the organism. Lipopolysaccharide is one of the most
important cell-surface polysaccharides, as it plays a key structural
role in outer membrane integrity, as well as being an important
mediator of host-pathogen interactions. The genetics for the
biosynthesis of the so-called A-band (homopolymeric) and B-band
(heteropolymeric) O antigens have been clearly defined, and a lot of
progress has been made toward understanding the biochemical pathways
of their biosynthesis. The exopolysaccharide alginate is a linear
copolymer of ß-1,4-linked D-mannuronic acid and L-guluronic acid
residues, and is responsible for the mucoid phenotype of late-stage
cystic fibrosis disease. The pel and psl loci are two recently
discovered gene clusters that also encode exopolysaccharides found to
be important for biofilm formation. Rhamnolipid is a biosurfactant
whose production is tightly regulated at the transcriptional level,
but the precise role that it plays in disease is not well understood
at present. Protein glycosylation, particularly of pilin and
flagellin, is a recent focus of research by several groups and it has
been shown to be important for adhesion and invasion during bacterial
infection.
Pseudomonas aeruginosa Virulence and Pathogenesis Issues
Regulation of gene expression can occur through cell-cell
communication or quorum sensing (QS) via the production of small
molecules called autoinducers. QS is known to control expression of a
number of virulence factors. Another form of gene regulation which
allows the bacteria to rapidly adapt to surrounding changes is through
environmental signaling. Recent studies have discovered that
anaerobiosis can significantly impact the major regulatory circuit of
QS. This important link between QS and anaerobiosis has a significant
impact on production of virulence factors of this organism.
Pseudomonas aeruginosa Biofilms: Impact of Small Colony Variants on
Chronic Persistent Infections
The achievements of medical care in industrialised societies are
markedly impaired due to chronic opportunistic infections that have
become increasingly apparent in immunocompromised patients and the
ageing population. Chronic infections remain a major challenge for the
medical profession and are of great economic relevance because
traditional antibiotic therapy is usually not sufficient to eradicate
these infections. One major reason for persistence seems to be the
capability of the bacteria to grow within biofilms that protects them
from adverse environmental factors. Pseudomonas aeruginosa is not only
an important opportunistic pathogen and causative agent of emerging
nosocomial infections but can also be considered a model organism for
the study of diverse bacterial mechanisms that contribute to bacterial
persistence. In this context the elucidation of the molecular
mechanisms responsible for the switch from planctonic growth to a
biofilm phenotype and the role of inter-bacterial communication in
persistent disease should provide new insights in P. aeruginosa
pathogenicity, contribute to a better clinical management of
chronically infected patients and should lead to the identification of
new drug targets for the development of alternative anti-infective
treatment strategies.
Antibiotic Resistance in Pseudomonas
Pseudomonas aeruginosa is a highly relevant opportunistic pathogen.
One of the most worrisome characteristics of P. aeruginosa consists in
its low antibiotic susceptibility. This low susceptibility is
attributable to a concerted action of multidrug efflux pumps with
chromosomally-encoded antibiotic resistance genes and the low
permeability of the bacterial cellular envelopes. Besides intrinsic
resistance, P. aeruginosa easily develop acquired resistance either by
mutation in chromosomally-encoded genes, either by the horizontal gene
transfer of antibiotic resistance determinants. Development of
multidrug resistance by P. aeruginosa isolates requires several
different genetic events that include acquisition of different
mutations and/or horizontal transfer of antibiotic resistance genes.
Hypermutation favours the selection of mutation-driven antibiotic
resistance in P. aeruginosa strains producing chronic infections,
whereas the clustering of several different antibiotic resistance
genes in integrons favours the concerted acquisition of antibiotic
resistance determinants. Some recent studies have shown that
phenotypic resistance associated to biofilm formation or to the
emergence of small-colony-variants may be important in the response of
P. aeruginosa populations to antibiotics treatment.
Iron uptake in Pseudomonas
Like all aerobic bacteria, pseudomonads need to take up iron via the
secretion of siderophores which complex iron (III) with high affinity.
Much progress has been made in the elucidation of siderophore-mediated
high-affinity iron uptake by Pseudomonas, especially in the case of
the opportunistic pathogen, P. aeruginosa. Fluorescent pseudomonads
produce the high-affinity peptidic siderophore pyoverdine, but also,
in many cases, a second siderophore of lesser affinity for iron. Some
of the genes for the biosynthesis and uptake of these siderophores
have been identified and the functions of the encoded proteins known.
Iron uptake via siderophores is regulated at several levels, via the
general iron-sensitive repressor Fur (Ferric Uptake Regulator), via
extracytoplasmic sigma factors/anti-sigma factors or via other
regulators. Since pseudomonads are ubiquitous microorganisms, it is
not surprising to find in their genome a large number of genes
encoding receptors for the uptake of heterologous ferrisiderophores or
heme reflecting their great adaptability to diverse iron sources.
Another exciting development is the recent evidence for a cross-talk
between the iron regulon and other regulatory networks, including the
diffusible signal molecule-mediated quorum sensing in P. aeruginosa.
http://en.wikipedia.org/wiki/Pseudomonas
http://en.wikipedia.org/wiki/Sphingomonas
CANADIAN TEEN DECOMPOSES PLASTIC BAG IN THREE MONTHS
http://blog.wired.com/wiredscience/2008/05/teen-decomposes.html
By Brandon Keim / May 23, 2008
"The Waterloo, Ontario high school junior figured that something must
make plastic degrade, even if it does take millennia, and that
something was probably bacteria. (Hey, at between one-half and 90
percent of Earth's biomass, bacteria's a pretty safe bet for any
biological mystery.)
The Record reports that Burd mixed landfill dirt with yeast and tap
water, then added ground plastic and let it stew. The plastic indeed
decomposed more quickly than it would in nature; after experimenting
with different temperatures and configurations, Burd isolated the
microbial munchers. One came from the bacterial genus Pseudomonas, and
the other from the genus Sphingomonas.
Burd says this should be easy on an industrial scale: all that's
needed is a fermenter, a growth medium and plastic, and the bacteria
themselves provide most of the energy by producing heat as they eat.
The only waste is water and a bit of carbon dioxide. Amazing stuff.
I'll try to get an interview with this young man who may have managed
to solve one of the most intractable environmental dilemmas of our
time.
And I can't help but wonder whether his high school already had its
prom. If he doesn't get to be king, there's no justice in this world."
AGREED: DANIEL BURD FOR PROM KING
http://apps.ysf-fsj.ca/virtualcwsf/projectdetails.php?id=1390
"My name is Daniel Burd, a grade 11 student at Waterloo Collegiate
Institute. I performed my first “science” experiment involving
planting and observing growth of different types of tomato seeds on
the balcony of our apartment in Waterloo eleven years ago. Since that
time, the ideas and concepts behind the way things work have
constantly aroused my interest and have posed numerous questions for
me to consider. At school, I am on ABCD Student Council, Charity
Controller, Environment club, a peer tutor, and Norse Star newspaper.
When I was five years old, I started to play the piano and I have
completed my grade 8 piano and grade 2 rudiments at the RCM.
Currently, I am learning improvisation and jazz. My jazz music role
model is Oscar Peterson. I am a member of Nordic Skiing club, ROW
swimming club and Waterloo Tennis Club where I am training for
tournaments. I am a volunteer at K-W Science and Technology Children’s
Museum. I help organize heritage events in K-W area and I run a
charity dog-walking business in my neighborhood for people with
disabilities. I fluently speak English, French and Russian and I enjoy
spending free time with my friends."
Awards
- The Manning Innovation Achievement Award - $500.00
- Dalhousie University Faculty of Science Entrance Scholarship
Senior Gold Medallist - $4000 Entrance Scholarship
- NSERC Undergraduate Student Research Award
Senior Gold Medallist - $5 625.00
- UBC Science (Vancouver) Entrance Award
Senior Gold Medallist - $4000 Entrance Scholarship
- University of Ottawa Entrance Scholarship
Senior Gold Medallist - $20,000 Entrance Scholarship
($5,000 each year for 4
years)
- Senior Silver Medallist - $3000 Entrance Scholarship
- The University of Western Ontario Scholarship
Gold Medallist - $2000 Entrance Scholarship
- The University of Western Ontario Scholarship
Silver Medallist - $1500 Entrance Scholarship
- Silver Medal - Environmental Innovation - $700.00
- Gold Medal - Biotechnology & Pharmaceutical Sciences - $1 500.00
- EnCana Platinum Award - Best Senior Project - $5 000.00
- EnCana Best in Fair Award - $10 000.00
Total $57 825.00
YEAST, TAP WATER, DIRT
http://news.therecord.com/article/354044
WCI student isolates microbe that lunches on plastic bags
BY Karen Kawawada
Getting ordinary plastic bags to rot away like banana peels would be
an environmental dream come true. After all, we produce 500 billion a
year worldwide and they take up to 1,000 years to decompose. They take
up space in landfills, litter our streets and parks, pollute the
oceans and kill the animals that eat them. Now a Waterloo teenager has
found a way to make plastic bags degrade faster -- in three months, he
figures.
Daniel Burd's project won the top prize at the Canada-Wide Science
Fair in Ottawa. He came back with a long list of awards, including a
$10,000 prize, a $20,000 scholarship, and recognition that he has
found a practical way to help the environment. Daniel, a 16-year-old
Grade 11 student at Waterloo Collegiate Institute, got the idea for
his project from everyday life. "Almost every week I have to do chores
and when I open the closet door, I have this avalanche of plastic bags
falling on top of me," he said. "One day, I got tired of it and I
wanted to know what other people are doing with these plastic bags."
The answer: not much. So he decided to do something himself. He knew
plastic does eventually degrade, and figured microorganisms must be
behind it. His goal was to isolate the microorganisms that can break
down plastic -- not an easy task because they don't exist in high
numbers in nature.
First, he ground plastic bags into a powder. Next, he used ordinary
household chemicals, yeast and tap water to create a solution that
would encourage microbe growth. To that, he added the plastic powder
and dirt. Then the solution sat in a shaker at 30 degrees. After three
months of upping the concentration of plastic-eating microbes, Burd
filtered out the remaining plastic powder and put his bacterial
culture into three flasks with strips of plastic cut from grocery
bags. As a control, he also added plastic to flasks containing boiled
and therefore dead bacterial culture.
Six weeks later, he weighed the strips of plastic. The control strips
were the same. But the ones that had been in the live bacterial
culture weighed an average of 17 per cent less. That wasn't good
enough for Burd. To identify the bacteria in his culture, he let them
grow on agar plates and found he had four types of microbes. He tested
those on more plastic strips and found only the second was capable of
significant plastic degradation.
Next, Burd tried mixing his most effective strain with the others. He
found strains one and two together produced a 32 per cent weight loss
in his plastic strips. His theory is strain one helps strain two
reproduce. Tests to identify the strains found strain two was
Sphingomonas bacteria and the helper was Pseudomonas. A researcher in
Ireland has found Pseudomonas is capable of degrading polystyrene, but
as far as Burd and his teacher Mark Menhennet know -- and they've
looked -- Burd's research on polyethelene plastic bags is a first.
Next, Burd tested his strains' effectiveness at different
temperatures, concentrations and with the addition of sodium acetate
as a ready source of carbon to help bacteria grow. At 37 degrees and
optimal bacterial concentration, with a bit of sodium acetate thrown
in, Burd achieved 43 per cent degradation within six weeks.
The plastic he fished out then was visibly clearer and more brittle,
and Burd guesses after six more weeks, it would be gone. He hasn't
tried that yet. To see if his process would work on a larger scale, he
tried it with five or six whole bags in a bucket with the bacterial
culture. That worked too. Industrial application should be easy, said
Burd. "All you need is a fermenter . . . your growth medium, your
microbes and your plastic bags." The inputs are cheap, maintaining the
required temperature takes little energy because microbes produce heat
as they work, and the only outputs are water and tiny levels of carbon
dioxide -- each microbe produces only 0.01 per cent of its own
infinitesimal weight in carbon dioxide, said Burd. "This is a huge,
huge step forward . . . We're using nature to solve a man-made
problem."
Burd would like to take his project further and see it be used. He
plans to study science at university, but in the meantime he's busy
with things such as student council, sports and music. "Dan is
definitely a talented student all around and is poised to be a leading
scientist in our community," said Menhennet, who led the school's
science fair team but says he only helped Burd with paperwork.
PEDIGREE
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=CTP_003309&use_sec=true&sec_url_var=region1
Microbes convert ‘Styrofoam™’ into biodegradable plastic /
02/23/2006
"Bacteria could help transform a key component of disposable cups,
plates and utensils into a useful eco-friendly plastic, significantly
reducing the environmental impact of this ubiquitous, but difficult-to-
recycle waste stream, according to a study scheduled to appear in the
April 1 issue of the American Chemical Society journal, Environmental
Science & Technology.
The microbes, a special strain of the soil bacterium Pseudomonas
putida, converted polystyrene foam — commonly known as Styrofoam™ —
into a biodegradable plastic, according to Kevin O’Connor, Ph.D., of
University College Dublin, the study’s corresponding author. The study
is among the first to investigate the possibility of converting a
petroleum-based plastic waste into a reusable biodegradable form.
O’Connor and his colleagues from Ireland and Germany, utilized
pyrolysis, a process that transforms materials by heating them in the
absence of oxygen, to convert polystyrene — the key component of many
disposable products — into styrene oil. The researchers then supplied
this oil to P. putida, a bacterium that can feed on styrene, which
converted the oil into a biodegradable plastic known as PHA
(polyhydroxyalkanoates). The process might also be used to convert
other types of discarded plastics into PHA, according to O’Connor.
PHA has numerous uses in medicine and can be used to make plastic
kitchenware, packaging film and other disposable items. The
biodegradable plastic is resistant to hot liquids, greases and oils,
and can have a long shelf life. But unlike polystyrene, it readily
breaks down in soil, water, septic systems and backyard composts.
Worldwide, more than 14 million metric tons of polystyrene are
produced annually, according to the U.S. Environmental Protection
Agency. Most of this ends up in landfills. Although polystyrene
represents less than 1 percent of solid waste generated in the United
States, at least 2.3 million tons of it is dumped in U.S. landfills
each year. Only 1 percent of polystyrene waste is currently recycled,
the authors note."
CONTACT
Kevin O' Connor, Ph.D.
www.ucd.ie/biocatal
e-mail: kevin....@ucd.ie
SEE ALSO
Anthony J. Sinskey, Sc.D.
http://web.mit.edu/biology/www/facultyareas/facresearch/sinskey.html
http://hst.mit.edu/public/people/faculty/facultyBiosketch.jsp?key=Sinskey
e-mail : asin...@mit.edu
Oliver Peoples, Ph.D. / Founder / Chief Scientific Officer, Metabolix
http://metabolix.com/
http://www.metabolix.com/natures%20plastic/coretechnology.html
http://www.metabolix.com/biotechnology%20foundation/biotechnologyfoundation.html
http://www.metabolix.com/sustainable%20solutions/sustainablesolutions.html
http://metabolix.com/resources/researchlinks.html
e-mail : peo...@metabolix.com
BIOPLAST
http://www.bioplast.com.tr/bioplast.html
http://www.bioplast.com.tr/bio-bozunur-plastics.html
PREVIOUSLY ON SPECTRE --- BIODEGRADABLE PLASTICS
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/a806584fe743400a/84334f2f76d7a48c?lnk=gst&q=PLASTIC#84334f2f76d7a48c
DOMESTICATING BIOTECH
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/10b613466cdccd56/10dd98161e8247ec?lnk=gst&q=BACTERIA#10dd98161e8247ec
GROW YOUR OWN BACTERIAL SLAVE ARMY --- SEA MONKEYS DONE FOR GOOD
http://groups.google.com/group/spectre_event_horizon_group/browse_thread/thread/338c3693773e818e/e27e7fa967783c03?lnk=gst&q=BACTERIA#e27e7fa967783c03
.
PSEUDOMONAS GENOME DATABASE
http://www.pseudomonas.com/
.
ALSO CAUSES SNOWFLAKES
http://www.efluxmedia.com/news_Bacteria_The_Main_Ingredient_in_Snowflakes_Scientists_Say_14620.html
Bacteria – The Main Ingredient in Snowflakes, Scientists Say
BY Max Brenn / February 29th 2008
One might rethink playing with snow or walking in the rain as a new
study by scientists from the Louisiana State University revealed that
snow and rain might form mostly on bacteria in the clouds. Scientists
have long known that the ice crystals in clouds, which become rain or
snow, need to cling to some kind of particle, called ice nucleators,
in order to form in temperatures above minus 40 degrees Celsius.
Microbiologist Brent Christner at Louisiana State University sampled
snow from Antarctica, France, and the Yukon and found that as much as
85 percent of the nuclei were bacteria, he said in a telephone
interview with the Associated Press. “Every snow and ice sample we’ve
looked at, we found biological ice nucleators. Here’s a component that
has been completely ignored to date,” Christner said. The most common
bacteria found was Psedomonas syringae, which can cause disease in
several types of plants (tomatoes, green beams and other similar
plants). The bacterium was found in 20 samples of snow from around the
world and subsequent research has also found it in summer rainfall in
Louisiana.
Scientists have sought ways to eliminate this bacterium in time. Now
they wonder whether this elimination would result in less rain or
snow, or would soot and dust be the major generators of precipitation.
“The question is, are they a good guy or a bad guy. And I don’t have
the answer to that,” Christner said, quoted by the same source. One
thing is for sure. Bacteria that infect plants may multiply on the
plants’ leaves and drift into the atmosphere. These bacteria could
then cause precipitation and land on another plant, where the life
cycle could continue, Christner said.
Virginia K.Walker, a biologist at Queen’s University in Kingston,
Ontario, Canada said other studies have found bacteria serving as snow
nuclei, but this is the first to identify it as Pseudomonas. “It’s one
of those great bacteria…you can find them anywhere. They are really
interesting,” Walker said. The study, supported by a Louisiana State
University research grant and by the National Science Foundation and
the Earth Institute at Columbia University, was published in today’s
edition of the journal Science
CONTACT
Brent C. Christner
http://www.biology.lsu.edu/faculty_listings/fac_pages/bchristner.html
http://brent.xner.net/
email : xn...@lsu.edu
ABSTRACT
http://www.biology.lsu.edu/highlights/christner.html
Ubiquity of Biological Ice Nucleators in Snowfall
"Despite the integral role of ice nucleators (IN) in atmospheric
processes leading to precipitation, their sources and distributions
have not been well established. We examined IN in snowfall from mid-
and high-latitude locations and found that the most active were
biological in origin. Of the IN larger than 0.2 micrometer that were
active at temperatures warmer than -7°C, 69 to 100% were biological,
and a substantial fraction were bacteria. Our results indicate that
the biosphere is a source of highly active IN and suggest that these
biological particles may affect the precipitation cycle and/or their
own precipitation during atmospheric transport"
.
ONE BILLION PER QUART
http://www.time.com/time/magazine/article/0,9171,894282,00.html
Bugs in the Reactor / Oct. 05, 1959
Los Alamos' Omega West is a swimming-pool-type research reactor whose
fuel rods are suspended under 25 ft. of water, which acts not only as
coolant and moderator but also shields its human operators from
radioactivity. In the spring of 1958, physicists peering down through
it saw that the water was getting cloudy. They called Chemist-
Bacteriologist Eric B. Fowler of the laboratory's radioactive-waste
disposal group, who found that it was swarming with microorganisms,
about i billion per quart. The bugs turned out to be rod-shaped
bacteria of the genus Pseudomonas, which were feeding on resin and
felt in the water purifying system.
The fierce radiation in the reactor appeared to bother the bacteria
hardly at all. When the reactor was shut down but still highly
radioactive, they multiplied fast. Even when it was running full
blast, they held their own. Since they normally divide every 20
minutes or so, this meant that radiation was killing only about as
many as managed to live and divide. Just how much radiation the
Pseudomonas got is hard to estimate, because the water circulates at
varying distances from the core of the reactor, but Dr. Fowler thinks
they may have absorbed more than 10 million rep (roentgen equivalent
physical) in an eight-hour day, which is 10,000 times the dose that is
fatal to man.
Many other microorganisms must have got into Omega West's deadly
water; only the Pseudomonas survived. Perhaps the Pseudomonas have
natural resistance to radiation. More likely, under the bombardment of
Omega's radiation, normal Pseudomonas underwent mutation, producing a
special strain capable of surviving in this atomic blast. This ability
to transform themselves quickly to cope with new conditions is a
specialty of humble bacteria, whose constitutions are relatively
simple. It is an ability that higher animals cannot emulate, but may
have reason to envy.
.
PSEUDOMONAS AND YOU
http://www.horizonpress.com/pseudo
http://www.horizonpress.com/gateway/pseudomonas.html
The Taxonomy of Pseudomonas
The studies on the taxonomy of this complicated genus groped their way
in the dark while following the classical procedures developed for the
description and identification of the organisms involved in sanitary
bacteriology during the first decades of the twentieth century. This
situation sharply changed with the proposal to introduce as the
central criterion the similarities in the composition and sequences of
macromolecules components of the ribosomal RNA. The new methodology
clearly showed that the genus Pseudomonas, as classical defined,
consisted in fact of a conglomerate of genera that could clearly be
separated into five so-called rRNA homology groups. Moreover, the
taxonomic studies suggested an approach that might proved useful in
taxonomic studies of all other prokaryotic groups. A few decades after
the proposal of the new genus Pseudomonas by Migula in 1894, the
accumulation of species names assigned to the genus reached alarming
proportions. At the present moment, the number of species in the
current list has contracted more than ten-fold. In fact, this
approximated reduction may be even more dramatic if one considers that
the present list contains many new names, i.e., relatively few names
of the original list survived in the process. The new methodology and
the inclusion of approaches based on the studies of conservative
macromolecules other than rRNA components, constitutes an effective
prescription that helped to reduce Pseudomonas nomenclatural
hypertrophy to a manageable size.
Genome Diversity of Pseudomonas aeruginosa
The G+C rich Pseudomonas aeruginosa chromosome consists of a conserved
core and a variable accessory part. The core genomes of P. aeruginosa
strains are largely collinear, exhibit a low rate of sequence
polymorphism and contain few loci of high sequence diversity, notably
the pyoverdine locus, the flagellar regulon, pilA and the O-antigen
biosynthesis locus. Variable segments are scattered throughout the
genome of which about one third are immediately adjacent to tRNA or
tmRNA genes. The three known hot spots of genomic diversity are caused
by the integration of genomic islands of the pKLC102 / PAGI-2 family
into tRNALys or tRNAGly genes. The individual islands differ in their
repertoire of metabolic genes, but share a set of syntenic genes that
confer their horizontal spread to other clones and species.
Colonization of atypical disease habitats predisposes to deletions,
genome rearrangements and accumulation of loss-of-function mutations
in the P. aeruginosa chromosome. The P. aeruginosa population is
characterized by a few dominant clones widespread in disease and
environmental habitats. The genome is made up of clone-typical
segments in core and accessory genome and of blocks in the core genome
with unrestricted gene flow in the population.
Oligonucleotide Usage Signatures of the Pseudomonas putida KT2440
Genome
Di- to pentanucleotide usage and the list of the most abundant octa-
to tetradecanucleotides are useful measures of the bacterial genomic
signature. The Pseudomonas putida KT2440 chromosome is characterized
by strand symmetry and intra-strand parity of complementary
oligonucleotides. Each tetranucleotide occurs with similar frequency
on the two strands. Tetranucleotide usage is biased by G+C content and
physicochemical constraints such as base stacking energy, dinucleotide
propeller twist angle or trinucleotide bendability. The 105 regions
with atypical oligonucleotide composition can be differentiated by
their patterns of oligonucleotide usage into categories of
horizontally acquired gene islands, multidomain genes or ancient
regions such as genes for ribosomal proteins and RNAs. A species-
specific extragenic palindromic sequence is the most common repeat in
the genome that can be exploited for the typing of P. putida strains.
In the coding sequence of P. putida LLL is the most abundant
tripeptide.
Genetic Tools for Pseudomonas
Genetic tools are required to take full advantage of the wealth of
information generated by genome sequencing efforts, and ensuing global
gene and protein expression analyses. Although the development of
genetic tools has generally not kept up with the sequencing pace,
substantial progress has been made in this arena. PCR- and
recombination-based strategies allowed construction of whole genome
expression and transposon insertion libraries. Similar strategies
combined with improved transformation protocols facilitate high-
throughput construction of deletion alleles and development of a broad-
host-range mini-Tn7 chromosome integration system. While to date most
of these tools and methods have been developed for and applied in P.
aeruginosa, they will most likely also be applicable to other
Pseudomonas with appropriate modifications.
Molecular Biology of Cell-Surface Polysaccharides in Pseudomonas
aeruginosa: From Gene to Protein Function
Cell-surface polysaccharides play diverse roles in the bacterial
"lifestyle". They serve as a barrier between the cell wall and the
environment, mediate host-pathogen interactions, and form structural
components of biofilms. These polysaccharides are synthesized from
nucleotide-activated precursors and, in most cases, all the enzymes
necessary for biosynthesis, assembly and transport of the completed
polymer are encoded by genes organized in dedicated clusters within
the genome of the organism. Lipopolysaccharide is one of the most
important cell-surface polysaccharides, as it plays a key structural
role in outer membrane integrity, as well as being an important
mediator of host-pathogen interactions. The genetics for the
biosynthesis of the so-called A-band (homopolymeric) and B-band
(heteropolymeric) O antigens have been clearly defined, and a lot of
progress has been made toward understanding the biochemical pathways
of their biosynthesis. The exopolysaccharide alginate is a linear
copolymer of ß-1,4-linked D-mannuronic acid and L-guluronic acid
residues, and is responsible for the mucoid phenotype of late-stage
cystic fibrosis disease. The pel and psl loci are two recently
discovered gene clusters that also encode exopolysaccharides found to
be important for biofilm formation. Rhamnolipid is a biosurfactant
whose production is tightly regulated at the transcriptional level,
but the precise role that it plays in disease is not well understood
at present. Protein glycosylation, particularly of pilin and
flagellin, is a recent focus of research by several groups and it has
been shown to be important for adhesion and invasion during bacterial
infection.
Pseudomonas aeruginosa Virulence and Pathogenesis Issues
Regulation of gene expression can occur through cell-cell
communication or quorum sensing (QS) via the production of small
molecules called autoinducers. QS is known to control expression of a
number of virulence factors. Another form of gene regulation which
allows the bacteria to rapidly adapt to surrounding changes is through
environmental signaling. Recent studies have discovered that
anaerobiosis can significantly impact the major regulatory circuit of
QS. This important link between QS and anaerobiosis has a significant
impact on production of virulence factors of this organism.
Pseudomonas aeruginosa Biofilms: Impact of Small Colony Variants on
Chronic Persistent Infections
The achievements of medical care in industrialised societies are
markedly impaired due to chronic opportunistic infections that have
become increasingly apparent in immunocompromised patients and the
ageing population. Chronic infections remain a major challenge for the
medical profession and are of great economic relevance because
traditional antibiotic therapy is usually not sufficient to eradicate
these infections. One major reason for persistence seems to be the
capability of the bacteria to grow within biofilms that protects them
from adverse environmental factors. Pseudomonas aeruginosa is not only
an important opportunistic pathogen and causative agent of emerging
nosocomial infections but can also be considered a model organism for
the study of diverse bacterial mechanisms that contribute to bacterial
persistence. In this context the elucidation of the molecular
mechanisms responsible for the switch from planctonic growth to a
biofilm phenotype and the role of inter-bacterial communication in
persistent disease should provide new insights in P. aeruginosa
pathogenicity, contribute to a better clinical management of
chronically infected patients and should lead to the identification of
new drug targets for the development of alternative anti-infective
treatment strategies.
Antibiotic Resistance in Pseudomonas
Pseudomonas aeruginosa is a highly relevant opportunistic pathogen.
One of the most worrisome characteristics of P. aeruginosa consists in
its low antibiotic susceptibility. This low susceptibility is
attributable to a concerted action of multidrug efflux pumps with
chromosomally-encoded antibiotic resistance genes and the low
permeability of the bacterial cellular envelopes. Besides intrinsic
resistance, P. aeruginosa easily develop acquired resistance either by
mutation in chromosomally-encoded genes, either by the horizontal gene
transfer of antibiotic resistance determinants. Development of
multidrug resistance by P. aeruginosa isolates requires several
different genetic events that include acquisition of different
mutations and/or horizontal transfer of antibiotic resistance genes.
Hypermutation favours the selection of mutation-driven antibiotic
resistance in P. aeruginosa strains producing chronic infections,
whereas the clustering of several different antibiotic resistance
genes in integrons favours the concerted acquisition of antibiotic
resistance determinants. Some recent studies have shown that
phenotypic resistance associated to biofilm formation or to the
emergence of small-colony-variants may be important in the response of
P. aeruginosa populations to antibiotics treatment.
Iron uptake in Pseudomonas
Like all aerobic bacteria, pseudomonads need to take up iron via the
secretion of siderophores which complex iron (III) with high affinity.
Much progress has been made in the elucidation of siderophore-mediated
high-affinity iron uptake by Pseudomonas, especially in the case of
the opportunistic pathogen, P. aeruginosa. Fluorescent pseudomonads
produce the high-affinity peptidic siderophore pyoverdine, but also,
in many cases, a second siderophore of lesser affinity for iron. Some
of the genes for the biosynthesis and uptake of these siderophores
have been identified and the functions of the encoded proteins known.
Iron uptake via siderophores is regulated at several levels, via the
general iron-sensitive repressor Fur (Ferric Uptake Regulator), via
extracytoplasmic sigma factors/anti-sigma factors or via other
regulators. Since pseudomonads are ubiquitous microorganisms, it is
not surprising to find in their genome a large number of genes
encoding receptors for the uptake of heterologous ferrisiderophores or
heme reflecting their great adaptability to diverse iron sources.
Another exciting development is the recent evidence for a cross-talk
between the iron regulon and other regulatory networks, including the
diffusible signal molecule-mediated quorum sensing in P. aeruginosa.
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