susceptibility of ultra-bacteria to heat?

Chris Fields cjfields at jove.acs.unt.edu
Mon Jul 12 20:21:14 EST 1999

Timothy Paustian wrote:
> David Lloyd-Jones wrote:
> >
> > Timothy Paustian <paustian at bact.wisc.edu>
> > >
> > > Ultrasmall bacteria are still controversial. They really haven't proven
> > > to many scientists that they do exist. I would speculate that they are
> > > as heat resistant as other bacteria, but that entirely depends upon the
> > species.
> > >
> >
> > I never thought of bacteria as coming in "species." Strains, surely. Or am I
> > wrong?
> >
> >                                                       -dlj.
> Splitting hairs wouldn't you say? Sure there are minor differences
> between some strains of bacteria, but I would suggest a species (E.
> coli) has a characteristic heat resistance. For example any strain of
> Pyrodictium occultum will be more heat resistant than any strain of Streptococcus.
> --
> Cheers,
> Timothy Paustian
> Univ.of Wisconsin-Madison
> Madison, WI
> http://www.bact.wisc.edu/gradstudies/paustian.html

This isn't entirely true, even for E. coli.  Don't forget that some
strains of E. coli are heat-sensitive (grow at 30 degrees only) due to
temp-sensitive lethal mutations.  Also, E. coli 0157:H7 is very
different from E. coli K12 (the genome size of the former is ~5.7 Mbp,
vs. 4.5 Mbp for K12) and is quite similar to Shigella dysenteriae, a
completely different genus (both produce Shiga toxin, other gene
products from similar pathogenicity islands).  One of the major
differences in E. coli and Salmonella is a large inversion in the ter
region of the chromosome; besides that, the two are very close.  BTW,
aren't you guys up there in Wisconsin sequencing 0157:H7 (Blattner's

I agree about splitting hairs.  I believe someone else in this thread
mentioned that bacterial evolution is probably best described as a
network instead of a tree (W. F. Doolittle had a great article in
Science from June 25 about this very thing).  So much gene swapping has
occurred (according to the genome projects,at least) that the lines
between genus, species, and strains are more blurry than ever.

C. J. Fields
Graduate Student, Dept. of Biological Sciences
The University of North Texas
Denton, TX 

email : cjfields at jove.acs.unt.edu
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