Preparing agar media with fungi and bacteria... ?

Hello, I have a few questions about preparing agar for fungal and
bacterial growth. I'm planning on growing fungi on the agar with
bacteria, however, I want to keep the bacterial populations relatively
low. I read somewhere that lowering the pH of the medium would suffice
in controlling bacterial growth while leaving the mycelium to grow in
peace. How would I go about lowering the pH to say 4-6? Is there a
particular base I should use?

Also, what else could I use to control bacterial growth, aside from
using antibiotics?

Much thanks,
nitrobacter

nitrobacter wrote:

Hi,

What kind of bacterium do you plan on growing on the plate? Often
standard fungal media such as SDA or similar will support the growth of
bacteria.

Where are your samples coming from? Why do you need the bacteria to grow
on there with the fungi? Because you could just add a specific number of
bacterial cells to the media... Or do you want confluent lawn of
slow-growing bacteria, rather than colonies?

Scott.

"nitrobacter" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...


OK so I think you need to be a bit more specific about what you are doing
and which organisms are involved.

What do you mean by keeping the bacterial populationS relatively low ?

Most mycological media comes with instruction for manufacture including
details of acidulant ( usually acidulants such acetic or lactic acid).

Mycological media which has been pH modulated tends to be selective not
only in realtion to Bacteria but also in terms of the typesof mould/yeasts
that will be supported.


Best n10

I'm planning to grow the isolated mycobionts of lichens. One group will
be growing in sterile environments, while the other will be growing with
bacteria (hopefully xenobionts). However, I do not want a slow-growing
glob of fungus sitting in the middle of several colonies of bacteria. So
what I'm hoping for is to keep bacterial growth slow enough to "match"
the slow growth of the mycobiont in culture.

Oh and sorry for the mistake in my original message, I meant lowering pH
with acid. ;p

Anyway, thanks again for your help.
-nitrobacter

"nitrobacter" <kazzmaster@hotmail.com> wrote in message
news:jYadnY2DT-u4UoHfRVn-qw@rogers.com...

Hi Nitro

You have a few options of which the most main stream is modulation of the
bacterial population with subl lethal
doses of antibiotics, included as a component of the agar.

For example I think that if you were to examine sample X on or in an array
of agar forumulations having Chloramphenicol levels
ranging between 0 and 25 ppm in 5 ppm incriments you would defintely
observe modulation of the bacterial population. The same could be achieved
with Oxyteracycline also.

Alterantively and conversly you might try Rosebengal Chloramphenicol agar
without supplimentation with Chloramphenicol. Rose bengal itself is only a
mild retardent of bacteria growth.

One obtuse way might be to feezeshock your mixed cultures with the hope of
differentially inducing a increased lag phase in bacterial growth.

How about microfiltration at say 45 20 10 5 2 micron. That should
retain the fungal (hyphal) loading whilst gradioently allowing passage of
"most" or some proportion of the bacterial population. Recover and culture
Voila.

How about calibrated centrifugation

The only other alternative I can think of is to play music in the lab which
only moulds like


I hope this helps


best N10