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Identification of bacterial growth

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Identification of bacterial growth

Postby Yeditepe » Sun Jun 26, 2011 9:25 pm

Hi,
I want to determine if there is any bacterial growth (small amount) in a mixture or not by using a chemical agent or any dye which gives a colour change when it react with any bacteria. Does anyone know what can I use? Thank you...
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Postby biohazard » Mon Jun 27, 2011 6:44 am

You need an agar plate with some nutrients or a tube of broth. Then dip a sterile loop into your sample, transfer some to you plate or tube and toss it into +37C overnight. Check for colonies on the plate or turbidity in the tube.

If nothing grows, try other temperatures. If still nothing grows, there is no bacteria or there is some more uncommon strain that cannot grow in "normal" environment (could be e.g. anaerobic bacterium).

There are other means to test for bacteria as well, but your question is a bit vague about the methods you are allowed to use.
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Re:

Postby Yeditepe » Mon Jun 27, 2011 3:32 pm

biohazard wrote:You need an agar plate with some nutrients or a tube of broth. Then dip a sterile loop into your sample, transfer some to you plate or tube and toss it into +37C overnight. Check for colonies on the plate or turbidity in the tube.

If nothing grows, try other temperatures. If still nothing grows, there is no bacteria or there is some more uncommon strain that cannot grow in "normal" environment (could be e.g. anaerobic bacterium).

There are other means to test for bacteria as well, but your question is a bit vague about the methods you are allowed to use.


Thanks for your reply but I do not want to check if there is any growth or not by using agar plate and wait for 24 hours. Let me explain my situation. I have a solution and I want to check if there is any microbial growth in it by observing any colour change (such as using any chemical which change its colour when it contacts with bacteria). I do not want to use turbidty. I want to use a compound or chemical. Thank you...
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Re: Identification of bacterial growth

Postby protold » Tue Jun 28, 2011 5:48 am

Hola, Phenol red 15mg/l is used for growth indicator in culture media, when the pH drops bu sugar metabolism the colour changes to orange. But this is clear with solutions with carbon sources where the formed CO2 drops the pH. but if there isn´t sugars and the carbon is extracted from aminoacids by deamination pH arise and the colour is more intense. Buena suerte
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Re: Re:

Postby biohazard » Tue Jun 28, 2011 6:00 am

Yeditepe wrote:...


Oops, my bad. I misread your original post and understood that you did not want to use a dye or a chemical compound.

Well, in this light phenol red might work indeed, though it is quite non-specific since it only detects the pH change. I cannot come up with any other such means right not, but I'll let you know if something occurs to me.

edit: You could look for some reagents that detect urea produced by bacteria, at least many clinical labs use that to detect bacterial growth.
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Postby Yeditepe » Tue Jun 28, 2011 7:25 pm

Thanks for the answers. The phenol red seems a good solution but the pH limits are limited. I know that it is a hard situation that determining bacterial growth without any specifity but if somebody remembers or know anything please let me know that would be useful. Thank you...
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Postby canalon » Tue Jun 28, 2011 10:36 pm

The Biolog Ecoplates (ww.biolog.com) whichh are useful to monitor bacterial and fungal growth in environmental samples rely on a tetrazolium dye that turns violet. so they do not rely on pH changes. might be worth looking into it.

I also vaguely remember that there was a technique to monitor continuously bacterial growth by the changes in the electrical conductivity of the broth. But I cannot remember the name, and a quick google search did not yield anything :(
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