Microbe Death/Lori

John Cherwonogrodzky jcherwon at dres.dnd.ca
Fri Apr 21 15:52:23 EST 1995


Dear Colleagues/Lori:
     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 
our environment.
     Yet how much is this true, how much is this an interpretation of 
exceptional conditions:
- 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 
seawater).
     - 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 
article....John



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