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Differences in colony size of bacteria on agar plates

Differences in colony size of bacteria on agar plates - Microbiology Forum

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  #1  
Old 09-06-2006, 07:38 PM
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Default Differences in colony size of bacteria on agar plates



why are there extreme differences in colony size of bacteria on agar plates if these were plated at the same time and are supposed to be of the same clone / strain?

thanks
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Old 09-06-2006, 08:35 PM
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Default Re: Differences in colony size of bacteria on agar plates

Do you mean that you have two "identical" plates that each has colonies of consistent size, but the colony sizes are different on the two plates, or that you have one plate that has colonies of different sizes on it?

For the first situation, I'd look at differences in how they were incubated or the composition of the plates (did the antibiotic get mixed in properly?). In the second situation, I'd examine the possiblity of satellite colonies (if amp was used) or try to restreak down to single cells.
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Old 09-07-2006, 02:53 AM
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Default Re: Differences in colony size of bacteria on agar plates

Hi
the difference in colony size is not very often. in most of the cases when we streak the same clone they have almos the same size on agar plate.
Yes! they have different size at some occassions, for example when you streak on plate then at the initial point of strak there is more colonies and at the end less. so due to large number at initial point and due to same amount of nutrients their size remain small as compared to colonies that are at the end of streak. but when you spread the bacteria on agar plate, this is not usually the case because the cells are almost uniformly distributed on plate, but if at some points they are more concentrated as compared to other place then their size remain small as i mentioned above.
some good comments are also given by Kmunson

more comments........
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Old 09-08-2006, 08:01 PM
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Default Re: Differences in colony size of bacteria on agar plates

Thank you both... I see this when I am streaking the same clone on agar plates.

This I guess may also be to the concentration of bacteria in the sample and uneven separation of the bacteria...

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Old 10-31-2010, 08:38 PM
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Default Re: Differences in colony size of bacteria on agar plates

astabac are u there i need ur help
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Old 10-31-2010, 08:38 PM
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Default Re: Differences in colony size of bacteria on agar plates

can u help me my friend i was wondering can u explain why is there different colony size for the same bacteria on the same plate
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Old 09-09-2011, 07:22 PM
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Default Re: Differences in colony size of bacteria on agar plates

there are some strange answers being given. You are not working with "cells" you are working with millions of bacteria that have formed into "colonies". You can't streak something down into individual cells unless you can fit under a microscope yourself and see individual bacteria.
The size difference of colonies is probably due to the number of that were there to begin with. If you started with ten million cells, that colony would be larger after an incubation period than if the colony started with 50,000 bacteria.
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Old 11-05-2011, 12:42 AM
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Default Re: Differences in colony size of bacteria on agar plates

The colonies should be generally be consistent. Are you sure you've not contaminated the plate or used a mixed inoculum?
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Old 12-08-2011, 08:42 AM
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Default Re: Differences in colony size of bacteria on agar plates

I am noticing something similar with the cultures i am working with. I work with drug-resistant and drug-susceptible strains of Mycobacterium tuberculosis and I've noticed that the colonies of some extensively- drug-resistant (XDR) strains appear much smaller than the drug-susceptible (DS) strains on non-antibiotic plates (7H11) as well as on plates that contain antibiotics (7H10) to which they are resistant. Note: Prior to ten-fold dilutions, both the DS and DR strains were back-diluted into fresh broth to achieve the same starting OD, yet the Day 0 plates show the XDR colonies are smaller than the DS colonies. Why is that?
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Old 12-10-2011, 02:37 AM
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Default Re: Differences in colony size of bacteria on agar plates

think the question asked after thecolonies from samestrin and clone. The resistant and senstive isolates would not be considered of the same clone.
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