Changes in cell-shape depending on the groth-phase?

John Kemp kemp at
Fri Feb 19 00:35:06 EST 1999


I was working with a lactobacillus bug that I was culturing out of the
proventriculus (a.k.a. the stomach) of parakeets.  I was conducting
morphometric analysis on them and noticed that they did in fact have a very
dynamic morphology.  They were a whopping 2 micrometers in vivo, and
subsuquently shrank to <1 micrometer.  I found that they progressively
decreased in both length and diameter (using electron micrographs). And no,
the changes were not uniform, so it was a situation VERY similar  to yours.
If you have any known constitutive biochemical characteristics that you
obtained with "pure" cultures, see if  your "questionable pure" cultures
yield similair or different results.
Also, electron microscopy  might show you distinct structural differences in
the two (or more) different bugs.  Well, these are just some simple ways to
determine if you have a contaminated culture.  You also mentioned
"un-expected growth".  If the colonies became macroscopic earlier than
usual...such is evidence of contamination.  I don't know if this helped
any.... but good luck.  I understand your frustration as I have been there
before.  Another alternative, which worked for me, is to pick another family
of bacteria to study..........  Just my .02 $

Michael Hofle

Karsten Karla wrote:

> Hi there!
> I´m new on this forum and I worry about some strange cell-morphologies
> concerning my bacteria.
> I´m working on a gram-negative halophilic strain which normally builds
> short rods of considerable size, compared with E.coli. Some days ago I
> took samples from the fermenter because of some unexpected growth. While
> watching the cells in the microscope I saw my normal short rods and some
> very long ones (around four to ten times longer than normal). I streaked
> a sample on agar and dilluted it over ten times in order to check
> whether there are two types of colonies, but I had no success, so I do
> not know if I got a contamination.
> My question is now: Are there any changes in cell-shapes depending on
> different growth-phases? May it be possible that the bacteria divide so
> fast, that they enter a new division-cycle before the former is
> finished? ...or do I only have a contamination which is difficult to
> isolate?
> Perhaps someone of you has some experience on things like that and could
> help me.
> Thank you.
> Best regards
> Karsten Karla

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