jcherwon at dres.dnd.ca
Fri Apr 21 15:52:23 EST 1995
Discover is a great magazine (broad topics reviewed, easy to read, well
researched and illustrated, etc.). Unfortunately, I don't know too much about
bacterial cell death and its mechanisms.
The little I do know seems to contradict general views. I've often read
of how bacteria die off when their nutrition is depeleted, the pH drops
because of acid build up, etc. Indeed, this cell death is often extended to
the human race with grim warnings of our own fate tied to our mis-treatment of
Yet how much is this true, how much is this an interpretation of
- Years ago I did my Ph.D. on Vibrio parahaemolyticus. Under the right
conditions (fresh media, aeration, good pH) it died in the fridge as it can't
take temperatures below 10 C (which is bizarre because in the ocean it
survives near freezing temp). This "bug" has a generation time of about 7
minutes (until then, the fastest bugs had times of 30 min) and yet if I left
agar medium plates at room temperature, put these in tied plastic bags to
prevent moisture loss and came back 3 YEARS later, the cells were viable. What
caused it to go into suspended animation. Years ago I offered a
non-metabolizable glucose polymer (isolated from Brucella and Agrobacter) to
Los Alamos Laboratories that needed a plasma extender for their work on
suspended animation of beagles, but I guess I was dismised as a "crank".
Another bizarre observation was that if this Vibrio was put in peptone
broths of different pHs that it didn't "like" (pH 6,7,9) it would metabolize
the peptone in a manner that the final pH was one it did like (pH 8, that of
- Some bacteria are "schizophrenic" in that they merrily go along in
a vegetative state, but when things get a little rough, they form spores which
can last decades, if not several centuries.
- The isolation of bacteria from core drillings has caused some
controversy. It is likely that they just wandered in there, carried by water
perculating through the sediments. There is another thought that perhaps these
have instead been sitting around for millions, if not billions, of years.
- When is a bacterium dead? Like that old study with pneumococcal DNA,
pathogenic cells killed with heat could still transform non-pathogenic cells.
In essence, a dead bacterium can still have its DNA change a living one so
that it comes back from the grave.
I hope this helps or at least gets enough rebuttals to help Lori with her
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