Re: Growth curves
Fri, 11 Oct 1996 16:33:11 -0400

In a message dated 96-10-10 19:38:58 EDT, you write:

<< I have found these types of curves interesting as well, though I don't
they are necessarily unextropian. I can envision a series of such curves in
succession. As the growth in one curve starts leveling off, new processes
(which I think can be viewed as extropian - BE, ST, IT ) take over and start
a new curve. >>

This in fact does happen with all microbial growth curves unless the
microorganism is a has very stable genetic population and does not "gene
switch" as _Candida albicans_ does (a yeast). _Candida has at least six (6)
gene switches it turned on of off depending of the environmental conditions.
So, I would hardly say a "yeast curve" was non-extropian.

Many (maybe all) bacteria, yeasts and mold also have two forms of
reproduction, sexual and asexual. This also accounts for the growth curves.

I discovered a new heat resistant mold my favorite growth curves are the heat
resistant bacteria and mold curves. They are different than classic growth
curves. If you try to count the number of viable cells in a population at
time zero. Then heat shock the cells (this kills the non-heat resistant
cells) and count the population again. . . with _Bacillus_ the counts go UP
not down. Some cells were viable but not countable (not culturable) before
the heat shock.

This is because some cells are shocked into growing and because some cells
are less heat resistant (and die), while others start growing faster (than
the weaker cells), thus giving a net INCREASE in count. Again, the growth
curve is affected by a non-homogeneous population.

This is why I don't get too worried by people pointing out the limits to
growth via growth curves. Life is not homogeneous, there is always an option
in the genetic pool and in our case the technological pool too. We have
evolving tools as well as biological systems.

You (Douglas Houts) are correct when you say the growth curves tend to
"step". Adaptation can take place any time, lag, log, stationary, or (yes
even) decline. If adaptation to a stress is seen in the decline phase it is
called the "Phoenix Phemomenon". This is will know to me since my research
is in cell injury and repair mechanisms and preservation systems for food,
cosmetics and pharmaceuticals.

The "stepping" is seen better in the log phase with several log-lags stepping
upward and upward as the weaker cells die and the adapted or gene-switched
cells out grow the previous population.

The cells start in lag phase (no net growth, equally numbers live as die)
then a log phase starts but soon reached what is normally seen as a
stationary phase. BUT it's not really stationary! It's another lag phase!
Then a second log phase started again. This is how I see humans lag-log
then stationary until trans-humans lag-log and post-humans lag-log then who
knows what will happen? And, I'm not just talking about biologic population
numbers (more is not better if quality of life is poor), I'm talking about
technology "stepping" evolution too.

When you consider biofilms (colonies of several kinds) of microorganism, the
growth curve does not even apply because the single cells (bacteria, yeasts
and molds) function as a multicellular organism just like we do.

Pure cultures are a figment of a microbiologist's imagination. Pure cultures
don't happen in nature (or are extremely rare and don't stay pure for long).


Publication List:

1. Enigl, Davin C. 1979. Isolation and Identification of Anaerobic Bacteria
from Normal and Diseased Human Oral Sites. University of Wisconsin. Library
of Congress Catalog: QR 100 E5.

2. Sorrells, Kent M., Davin C. Enigl and John R. Hatfield. 1989. Effect of
pH, Acidulant, Time, and Temperature on the Growth and Survival of Listeria
monocytogenes. Journal of Food Protection 52: 571-573.

3. Sorrells, Kent M. and Davin C. Enigl. 1990. Effect of pH, Acidulant
Sodium Chloride and Temperature on the Growth of Listeria monocytogenes.
Journal of Food Safety 11: 31-37.

4. Enigl, Davin C., A. Douglas King and Tomas Török. 1993. Talaromyces
trachyspermus , A Heat-Resistant Mold Isolated From Fruit Juice. Journal of
Food Protection 56: 1039-1042.

5. Orth, D.S. and Davin C. Enigl. 1993. Preservative Efficacy Testing by a
Rapid Screening Method for Estimation of D-values. Journal of the Society of
Cosmetic Chemists 44: 329-336.

6. Enigl, Davin C. and Kent M. Sorrells. In Press, 1996. Water Activity and
Self-Preserving Formulas. In: Preservative-Free and Self-Preserving Cosmetic
and Drug Products. Jon J. Kabara and Donald S. Orth, Eds. Marcel Dekker,
Inc. New York, NY.

Davin C. Enigl, MS-MEAS, President-Microbiologist
HACCP Validations-sm Hazard Analysis and Critical Control Points for the
Food, Cosmetic, Pharmaceutical, and Nutritional Supplement Industry
Voice: (916) 989-8264, Fax: (916) 989-8205, Pager: (714) 725-7695
9040 Erle Blunden Way
Fair Oaks, CA 95628
October 11, 1996
9:51 am