heat-resistant bacteria fouling pure cultures of fungi

Stamets 1 stamets1 at aol.com
Sat Dec 24 15:36:32 EST 1994

Fellow Mycologists

On heat resistant bacteria fouling pure cultures:

Just what could be a helpful note. Most of you making culture
media for fungi autoclave for 30-45 minutes at 15 psi (1kg/cm-2).
Most use wisely use filtered/purified water. I usually do not. 
With the massive rains we have had here in the
 past 3 weeks - the worst flooding in 75 years - 
the ground water has become
unusually rich with sediments/nutrients,
 causing a bacterial bloom, an order of magnitude
 greater than that which I have seen in years.
 Running parallel trials, I was shocked to find
that malt extract agar media "spontaneously"
 contaminated with bacteria after 2 1/2 hours of autoclaving.
 The contaminating agents appeared 3 weeks after pouring.
 So goes the concept of "sterilization".
 Clearly, the more contaminants at the front end of the
process, the more which survive, post treatment.
 We have had to return to osmosis-filtered water,
 which, for a production facility is not without its limitations. 

A friend in Europe, Peter Oei, author of several books on 
mushroom cultivation, e-mailed me with what appears to be
a similar  problem. Collectively, we have more than 40 years
of culture experience. This is the first time we both have 
seen this. I can only wonder - Could bacteria with greater
 heat tolerance be evolving? Is world-wide ground water contamination and
nutrient flow creating a new environment for the evolution of
these bacteria? 

   How many physcians really comprehend what "sterilization"
means. Most hospital disposal programs for destruction of pathogens
would not compare favorably with my experiences.Do I sound alarmist?
Are my concerns unjustified, unscientifically based. I invite your 
comments - especially from bacteriologists. 

     On another matter, have any of you heard about
 "gene migration" of antibiotic-resistant properties of bacteria
 which have not been directly to antibiotics exposed? 

    Evolution is a powerful force. I can only wonder at what
unwitting participation humans, laboratories, hospitals, day
care centers, and immunized populations play in the evolution
of new generation pathogens.

 On that hopeful note, I remain humbled by the power of the
invisible landscape. 

Happy New Year! 

paul stamets

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