E. coli competence

Richard heath at mbcf.stjude.org
Thu Sep 29 12:22:37 EST 1994


In article <36979t$7tf at charm.magnus.acs.ohio-state.edu>, aottolen at magnus.acs.ohio-state.edu (Abramo C Ottolenghi) writes:
> The drop between the two peaks can be explained physiologically.  If as I 
> suspect the cells are in "near" synchrony, there might be a point inthe cell 
> cycle at which they might be more amenable to becoming competent.  There is 

An interesting idea.  Do the peaks in the competency fall one doubling time 
apart?  I can't find my copy of the paper, but remember the graph as being 
competency vs. OD. (I'm also not used to OD, we use Kletts!!).  How synchronous
are the cells when the culture is inoculated?  How long do they remain
synchronous?  Others at St Jude are working on cell cycles of mammalian cells -
when growth factor is re-introduced, the first cycle is synchronous, the second
less so, and by the third, the cells are no longer synchronous.  Does this
apply to _E. coli_ too???  

This still leaves the question, if synchronicity is the answer, as to why the
second competency peak is bigger than the first.  Is this due to higher cell
density, or what?  If the cells could be kept synchronous for longer, would the
peaks keep getting higher???   

> evidence that the phospholipids of the membrane change when  it has to
> curve for septation. (several papers by Vic Norris of the University of
> Leicester.

The overall phospholipid composition doesn't change, but the local make up may
do so.  Their is growing evidence that acid phospholipids (phosphatidylglycerol
and cardiolipin) are required for the initiation of DNA replication at oriC
(Kornberg; Shapiro; Dowhan as well as Norris I think.  Don't have the refs to
hand, but remember see a poster by Weiming Xia and Bill Dowhan at the ASBMB
conference).  Hasn't Shapiro, and Rothfield, published about "polarised" cells
too.  There are obviuosly changes in the physiological state of cells at
septation, leading to localization of FtsZ (which forms a ring at the site of
septation).  What are the signals that cause this?  And are these
signals/changes responsible for the increase in competency (to get back to the
original thread)?  :-) 

> 
> Abramo Ottolenghi.  Ohio State University
> aottolen at magnus.acs.ohio-state.edu

Well, I've had some fun!  All the above ideas are pretty unresearched, so feel
free to shoot me down.  

Richard Heath, Ph.D.
St Jude Children's Research Hospital,
Department of Biochemistry,
Memphis TN 38101
heath at mbcf.stjude.org




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