Homemade growth media
Alexander Avtanski
Here comes a biology question from a software
engineer, so please, have some patience with
me, :-) ...
Is there a simple way to make bacterial growth
media (for petri dishes) at home? Me and my
7-year old daughter were experimenting for fun
to try to breed anything (no matter what) on a
gelatin-based media.
Please, don't laugh - we tried to use Jell-O
with some extra sugar. Nothing grows on this,
I'm tellin' ya! This can stay fresh forever,
it's more durable than the pyramids. I don't
know what they put in the Jell-O, but it's now
well past a week in dark and warm conditions -
fresh as a pickle, not a spot on it. Tried
about 10 different "cultures" on it - nothing
eats this stuff!
My guess is that one of the problems is that
the pH is too low. Also, maybe we should've
added some salt.
Any help? Any recipes with ingredients that
I can find easily?
Regards,
- Alex
JEDilworth
Some bacteria hydrolyze gelatin and break it down. Agar media is the
best, but to make media you have to have some way to sterilize it. I
assume you don't have an autoclave at home. Agar is also tricky to melt
down and work with as it burns easily. You need to heat it to boiling,
let it boil for a minute while swirling, and then take it off the heat
or it burns really quickly. It also can boil over and cause a hot mess.
Then you have to sterilize it before pouring plates.
http://scientificsonline.com/Product.asp_Q_pn_E_3081422 You can buy
this stuff online from Edmund Scientific, but you still have to have a
way to sterilize it.
If you want to grow fungus, cut a potato in half and leave it out for a
few days. Potatoes grow fungi very well. We use potato dextrose agar in
the lab to subculture fungi for identification. You could also try Knox
gelatin blocks and see how that works. Don't add anything to it.
Speaking as a microbiologist, you probably don't want to get into
anything more than that. Disposal is a problem if you grow bacteria in
large amounts. If you start swabbing hands and noses you will invariably
come up with Staph. aureus (i.e. Staph infections) and you don't want to
be messing with that. Dirt bacteria are pretty safe. Don't start
swabbing toilets, noses, or mouths, however.
Take my word for it - bacteria at home is not a good idea. Grow a few
fungi and let it go at that.
Judy Dilworth, M.T. (ASCP)
Microbiology
"Alexander Avtanski" <avta...@ispwest.com> wrote in message
news:rvmdnYISCpP...@comcast.com...
> Hello,
John Gentile
My guess is that the amount of sugar (in the form of sucrose) in your
gelatin is now at a toxic level for any bacteria to grow. You are
probably better off using a sugar free gelatin.
I agree with Judy - doing home experiments with bacteria can lead to
really bad outcomes. When you finish with everything be sure you
submerge all your plates and growths in a solution of 5 % bleach and
water. You can add a little bit of dish soap to make the solution
penetrate a little better.
--
John Gentile
Editor
Rhode Island Apple Group
Alexander Avtanski
> [ ... ]
> Is there a simple way to make bacterial growth
> media (for petri dishes) at home? Me and my
> 7-year old daughter were experimenting for fun
> to try to breed anything (no matter what) on a
> gelatin-based media.
Thanks Judy & John for your answers. I didn't imagine
that common bacteria could be dangerous - so we will
probably stick with the potato & fungi.
Later we could possibly try some "dirt bacteria" on a
sugar-free gelatin, but now I'm not so sure about it.
Just from curiosity - what makes the bacteria (that
was not causing any problems before) dangerous, when
we "breed" it in a colony? The bigger quantity and
concentration of bacteria, or it is something else?
Thanks,
- Alex
JEDilworth
isolated enough from other cells or microconidia. When you give bacteria
or fungi media to grow on, this is like giving them a gourmet meal. One
cell can rapidly become millions of cells. Staph. colonies like the ones
in the picture below only take 12-18 hours to grow at 37 degrees C (98.6
degrees F):
http://www.asta-tiho.de/mibi/Diagnostik/Staph%20aureus%20BA.jpg
Here is a photo of Staphylococcus aureus on a blood agar plate (we use
5% sheep blood agar in the laboratory as a basic medium for bacteria).
There is LOTS of Staph. on this plate. You will notice that the
streaking eventually isolates individual colonies. One colony arises
from one cell, hence that colony represents a pure culture of the
organism. This is how microbiology people subculture pathogenic bacteria
for identification and antibiotic testing. We perform it on a pure
culture. It's one thing to do this in a lab setting; it's quite another
to have this much bacteria in your kitchen! Your garbage men really
wouldn't appreciate these plates in the garbage, believe me. We use
special biohazard waste companies to dispose of our plates and media.
A certain percentage of the human population carry bacteria, such as
Staph. aureus, in their noses or nasopharyngeal area. It doesn't
necessarily cause problems there. Staph. infections, however, are nasty
and you may inadvertently grow it on your homemade media and now know
what it is. However, if you start swabbing areas of the body such as the
nose and skin, inoculate those swabs onto home made media, you may
inadvertently stick your finger in the colonies and then into your eye
or other mucus membrane areas, you could end up with a quite nasty
infection.
http://tinyurl.com/cf7hz (Staph. infection of a finger, which could
obviously spread to other places....)
Couple this with a 7 year old child - as I recall my daughter, when she
was seven, didn't really understand the concept of hand-washing or basic
hygiene all that well. Kids are always sticking their fingers in their
mouths and eyes and noses and smearing their hands around on other
things. Take my word for it - you DON'T want to be messing with
bacterial colonies with children in the house.
I took some large agar plates into my daughter's sixth grade classroom
years ago. I had one of the kids put their hand onto the plate. I then
took it back to the lab and incubated it overnight and brought it back
the next day. Believe me - kids' hands are pretty filthy. The sixth
graders only slightly grasped what micro was about. It's a very
complicated subject.
Please remember, after all these warnings, that only about 10% of
bacteria are human pathogens. Bacteria are everywhere in the
environment, and we need them to be there. That is why I cautioned you
about not culturing human sources - because of the colonization problem,
and the danger of finding colonized pathogens.
All this being said, we could not live without bacteria. We carry an
enormous load of bacteria around with us on a daily basis; in our guts
and our mouths and on our skin. We could not live without our "normal
flora" or we'd be like the Bubble Boy on Seinfeld reruns. It's when
these bacteria get outside their normal place of residence is when they
start to cause problems.
Have fun with your potatoes. I would suggest a room temperature setting
for your potato experiment. We incubate our fungi at 25-30 degrees C
(77-86 degrees F). If your temp is lower than that, you may get very
slow growth. This is why refrigeration works so wonderfully! However,
I'm sure you've pulled moldy objects out of your fridge - mold will
grow, just not very quickly.
Happy Thanksgiving!
Judy Dilworth, M.T. (ASCP)
Microbiology
"Alexander Avtanski" <avta...@ispwest.com> wrote in message
> Just from curiosity - what makes the bacteria (that
Lesley Robertson
>
> Just from curiosity - what makes the bacteria (that
> was not causing any problems before) dangerous, when
> we "breed" it in a colony? The bigger quantity and
> concentration of bacteria, or it is something else?
>
to this discussion. I agree heartily with everything that Judy and John have
said - we don't even allow 1st year microbiology students to play with
bacteria isolated from people. Part of the problem is numbers - one or two
may be dealt with by the body before they can do much, but a colony contains
millions. If they came from a human sample, you then have millions of bugs,
all happily able to grow in the conditions provided by a mammalian body
(which is why it's not a good idea to use samples from family pets either).
Most healthy people carry some of these bugs in their noses, etc - and when
their resistance is low, the things get a chance and get going - result is
(at best) sore throats, etc. Swabs from toilets, etc, would be worse - for
example, a favourite bug in laboratories is called E. coli. Because we all
use it so much, we tend to forget that the lab strain is just one strain
(version) which is known to not be dangerous. E. coli's idea of an ideal
home is the mammalian gut, and some strains can kill, usually via food
poisoning (there were a few deaths from an outbreak in Wales in the summer).
One thing we do when we have an open day is prepare fungal plates - if you
can get seome gelatine, mix some with a sugary substance, and some more with
liquid from dissolving stock cubes (in Europe, OXO does well). When the
plates are set, sprinkly a little ground pepper over the surface and wait a
week. You'll get gardens of beautiful fungi. If you make different sorts of
gel, you can see if you get different sorts of fungi from the same pepper...
My 1st years also try other spices - cloves do well, cinnamon doesn't. Get
yourself a good hand lens if you don't have access to a microscope - fungi
are very beautiful when magnified.
Good luck!
Lesley Robertson
http://www.beijerinck.bt.tudelft.nl
Patrick Duriez
> Gelatin media has a tendency to get squishy when bacteria grows on it.
> Some bacteria hydrolyze gelatin and break it down. Agar media is the
> best, but to make media you have to have some way to sterilize it.[...]
A simple pressure cooker is fine. Count 20 minutes when the steam start
to get out and you got sterile medium. Even better, it will melt the
agar without burning it. But prepare it in a bottle that 50 to 60% full
if you do not want to have too much boiling over. And have a
bottle/recipient that can withstand the heat (regular glass bottle are
likely too explode...) and not tightly closed too allow pressure
equalization (otherwise it will explode too..).
> Speaking as a microbiologist, you probably don't want to get into
> anything more than that. Disposal is a problem if you grow bacteria in
> large amounts. If you start swabbing hands and noses you will invariably
> come up with Staph. aureus (i.e. Staph infections) and you don't want to
> be messing with that. Dirt bacteria are pretty safe. Don't start
> swabbing toilets, noses, or mouths, however.
>
> Take my word for it - bacteria at home is not a good idea. Grow a few
> fungi and let it go at that.
I have to agree with that. Be rally carefull. I have worked with some
bacteria isolated from healthy individual... most of them were carrying
genes involved in one pathology or another.
--
Patrick
Alexander Avtanski
> [ ... ]
> A simple pressure cooker is fine. Count 20 minutes when the steam start
> to get out and you got sterile medium. Even better, it will melt the
> agar without burning it. But prepare it in a bottle that 50 to 60% full
> if you do not want to have too much boiling over. And have a
> bottle/recipient that can withstand the heat (regular glass bottle are
> likely too explode...) and not tightly closed too allow pressure
> equalization (otherwise it will explode too..).
>
>>Take my word for it - bacteria at home is not a good idea. Grow a few
>>fungi and let it go at that.
>
> I have to agree with that. Be rally carefull. I have worked with some
> bacteria isolated from healthy individual... most of them were carrying
> genes involved in one pathology or another.
The more I look at it, the more I don't like the idea to try
anything with bacteria. Pressure cookers, unknown pathogenes -
these doesn't sound safe around a 7-year old. We will stick to
the fungi. This sounds safer. :-)
- A
Alexander Avtanski
> [...]
> One thing we do when we have an open day is prepare fungal plates - if you
> can get seome gelatine, mix some with a sugary substance, and some more with
> liquid from dissolving stock cubes (in Europe, OXO does well). When the
> plates are set, sprinkly a little ground pepper over the surface and wait a
> week. You'll get gardens of beautiful fungi. If you make different sorts of
> gel, you can see if you get different sorts of fungi from the same pepper...
> My 1st years also try other spices - cloves do well, cinnamon doesn't. Get
> yourself a good hand lens if you don't have access to a microscope - fungi
> are very beautiful when magnified.
> Good luck!
> Lesley Robertson
> http://www.beijerinck.bt.tudelft.nl
Ground perrer? Other spices? Wow... Now THAT sounds fun to
try!
One thing I didn't get here: What do you mean when you say
"liquid from dissolving stock cubes"? What is "OXO"?
Regards,
- Alex
Alexander Avtanski
I mean "pepper". Sorry.
- Alex
JEDilworth
believe, of beef stock that comes in cubes. In the US, Weyler makes beef
and chicken bouillon cubes, and there are other companies that make
dehydrated beef stock. Chances are you have some in your cupboard right
now! These are fairly salty, so I don't know how much you would use to
enrich your gelatin. The sugar will support fungi in the gelatin.
Enrichment with beef broth will enable more stuff to grow.
That's very interesting about the spices. We'll have to try that in the
lab some time and see what comes up.
Don't get real real close to the colonies, though. as you don't want to
breath in the microconidia. In the lab, we do all fungus work in a bio
safety cabinet, as fungi from humans tends to be more pathogenic.
Have fun.
Judy Dilworth, M.T. (ASCP)
Microbiology
Trond Erik Vee Aune
> The more I look at it, the more I don't like the idea to try
> anything with bacteria. Pressure cookers, unknown pathogenes -
> these doesn't sound safe around a 7-year old. We will stick to
> the fungi. This sounds safer. :-)
I agree.
As an undergraduate I got very interested in microbiology. I started
taking used petri dishes home after microbiology lab class and then
recirculated the plates. I made medium in my dorm kitchen with agar
bought from some exotic grocery store. And I used the floor heating in
our bath room as an incubator. All in all it was very funny and
interesting, but as soon as I asked my microbiology professor for some
technical advice he urged me to stop this and instead offered me a lab
space in his own lab. And that's pretty much where I am now :).
Trond Erik
--
Trond Erik Vee Aune
Department of Biotechnology, NTNU
http://www.biotech.ntnu.no/molgen
- Must be sad being a dyslectic, agnostic insomniac, lying
awake during the night, wondering if there really is a dog
a...@example.com
> media (for petri dishes) at home? Me and my
> 7-year old daughter were experimenting for fun
> to try to breed anything (no matter what) on a
> gelatin-based media.
With a 7 yr old, I wouldn't. Maybe a really responsible high school kid,
with proper equipment and if all involved knew what they were doing. It's
a little too easy to pick up and grow some nasties accidentally.
But you could still do some culture work with her, and have fun at
the same time... Yoghurt, for instance, is milk with a mixed bacterial
culture; sauerkraut, fermented pickles, kefir, vinegar... many foods
have specific bacterial cultures. Yoghurt and yoghurt cheese are both
easy to make, and you can use grocery store yoghurt "with active cultures"
as your inoculum.
http://ianrpubs.unl.edu/dairy/g449.htm
http://www.bbc.co.uk/dna/h2g2/A317053
Lesley Robertson
>
> One thing I didn't get here: What do you mean when you say
> "liquid from dissolving stock cubes"? What is "OXO"?
>
or a thick paste of either meat or yeast extract used by some people to add
flavour to casseroles. In Europe they come with a range of names, OXO being
one of them. Also Marmite, Knorr,...
Lesley Robertson
Lesley Robertson
"JEDilworth" <bact...@nospamhortonsbay.com> wrote in message
news:rd6dnRLHSMM...@buckeye-express.com...
>
> That's very interesting about the spices. We'll have to try that in the
> lab some time and see what comes up.
>
> Don't get real real close to the colonies, though. as you don't want to
> breath in the microconidia. In the lab, we do all fungus work in a bio
> safety cabinet, as fungi from humans tends to be more pathogenic.
>
for inexperienced students, etc) I use black pepper - trying other spices is
an attempt to make the prac more interesting.
My next group is also going to try green tea - I'm told that it gives nice
colonies.
The big problem is always to find things that will provide level 1 (GRAS)
bugs that are suitable for 1st years to play with.
BTW I've use OXO at about half the strngth suggested for cooking and that
worked OK.
Lesley Robertson
Alexander Avtanski
We were away for a couple of days - that's why I reply with a delay.
JEDilworth wrote:
> I think Lesley is referring to bouillon cubes. OXO is a brand, I
> believe, of beef stock that comes in cubes. In the US, Weyler makes beef
> and chicken bouillon cubes, and there are other companies that make
> dehydrated beef stock. Chances are you have some in your cupboard right
> now! These are fairly salty, so I don't know how much you would use to
> enrich your gelatin. The sugar will support fungi in the gelatin.
> Enrichment with beef broth will enable more stuff to grow.
Now I understand. Thanks. Yes, we have something like this at home.
But I think we don't need it, because...
> That's very interesting about the spices. We'll have to try that in the
> lab some time and see what comes up.
... because when we got home today, we looked at the Jell-O jar where,
before we left, we had put some ground black pepper (and red pepper
too, just in case I misunderstood Lesley). There was a small, round
fuzzy patch growing in there. A "black pepper fungi" forest!
Thanks! :-)
- Alex
P.S. This is a first for me. Enjoying the look of spoiled food, I
mean, :-)
Mike McWilliams
different zones grow different things, and you don't even have to open it.
Richard Mateles
with aspartame or equivalent). Avoid human pathogens by not culturing
samples from the human body or sewage. Take a pinch of earth, stir it with
water, and put a drop on a plate, and spread the drop. Lesley's pepper is a
good source of a varied flora also.
You'll get various colonies forming on incubation at room temperature or a
little warmer (but below the melting popint of gelatin).
Don't be too paranoid about setting off epidemics, but don't taste the
plates or colonies.
The nice thing about gelatin vs. agar is gelatin is easy to melt--agar
requires more work.
Rich Mateles
"Alexander Avtanski" <avta...@ispwest.com> wrote in message
news:rvmdnYISCpP...@comcast.com...
Lesley Robertson
"Richard Mateles" <rmat...@candida.com> wrote in message
news:rsmjf.1934$Zb2....@newssvr23.news.prodigy.net...
>
> The nice thing about gelatin vs. agar is gelatin is easy to melt--agar
> requires more work.
But, with samples, you have to be VERY careful how you pick the plates up! I
found a note in Beijerinck's lab journal saying that he got better results
with some bugs if he used gelatine rather than agar, so tried it with
photobacters we were growing. He was quite right - we got more light from
the bugs, but they also ate the gelatine, and when I picked the plate up
incautiously, the whole contents ran straight down my arm!
Lesley Robertson