E. coli competence

mcgeed at HAL.HAHNEMANN.EDU mcgeed at HAL.HAHNEMANN.EDU
Wed Sep 21 16:55:47 EST 1994


From:	MX%"mcgeed at hal.hahnemann.edu" 21-SEP-1994 14:31:35.05
To:	MX%"microbiology at net.bio.net"
CC:	
Subj:	E.coli competence

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From: mcgeed at hal.hahnemann.edu
Subject: E.coli competence
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From:	HAL::MCGEED       21-SEP-1994 13:52:50.90
To:	MX%"microbiology at net.bio.net"
CC:	MCGEED
Subj:	E. coli competence

	You bring up an excellent point about cell-cell communication.  There
is a well-documented literature on the communication of bioluminescent 
bacterial cells with one another as the cell density increases.  The
bioluminescent bacteria Vibrio harveyi and Vibrio fischeri increase
dramatically under aerobic conditions during mid-log phase of growth, due to
the increase in a compound known as autoinducer.  As the name suggests, cells
secrete the compound into the extracellular environment and the compound then
acts on a receptor molecule (LuxR) which enhances the bioluminescence operon
(lux).  Interestingly, the autoinducer from V. fischeri does not induce
bioluminescence in V. harveyi and vice versa; i. e. the autoinducers in these
species are distinct compounds.  The autoinducers are small organic molecules
with an amino acid analog (one is called beta-hydroxybutyryl homoserine
lactone; I forget the name of the other).  
	A simple way to test for the possible presence of autoinducer in 
E. coli, one would grow up the bugs to mid-log phase, remove all cells from the
media, and then add a known amount of E .coli to this broth and the same amount
to a fresh broth.  If the buggers grow faster in the first broth, then it is
likely that autoinducer(s) are made in E. coli.  
	Still another Gram (-) bacteria [bioluminescent bacteria are Gram (-)] 
-Pseudomonas aeruginosa- also has been shown to produce autoinducer (I believe
this is Barbara Iglewski's work), although I don't know much about this case.

	Isn't this fascinating that these buggers REALLY communicate with one
another as a group effort?  From an evolutionary standpoint, one might
speculate that advancement to the eucaryotic realm may, in part, be due to the
selective advantage that some cells in a population have due to production of
autoinducers!

	Perhaps others could elaborate further?...I've already taken up too
much time!	


David McGee
Medical College of Pennsylvania and Hahnemann University
Dept. Microbiology and Immunology
e-mail:  mcgeed at hal.hahnemann.edu
phone: 215-762-8275



David J. Mcgee
MCGEED at hal.hahnemann.edu





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