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Re:Starving Bacteria
The exerpt below is taken from an article in the October, 1996, Scientific
American:
Microbes Deep Inside the Earth
by James K. Fredrickson and Tullis C. Onstott
....How do microorganisms manage to persevere for so long? In some
cases (for example, SLiMEs), bacteria can survive because the essential
nutrients are constantly renewed; although in most other sorts of
formations, food and energy sources are relatively scarce. Nevertheless,
the resident bacteria appear to have adapted to these rather spartan
living conditions. Bacteria must rely on internal reserves during periods
of long-term starvation (as do higher organisms), and most types of
bacteria shrink from a healthy size of a few microns to less than a
thousandth of their normal volume as they use up their stores. Thomas
L. Kieft of the New Mexico Institute of Mining and Technology has
found that such tiny, starved microbes (called dwarf bacteria or
"ultramicro-bacteria") commonly inhabit the subsurface.
The metabolic rate of such starved bacteria is probably much lower than
when they are well fed. As a result, the average frequency of cell
division for a subsurface microbe may be once a century, or even less,
whereas surface microorganisms reproduce in a matter of minutes,
hours, days or, at most, months. Microorganisms living in the deep
subsurface limit their metabolism in order to endure starvation for
geologically significant lengths of time. These bacteria can remain
viable at little or no metabolic cost.
The sluggish pace of microbial metabolism in the subsurface makes it
difficult to define just how many of the bacteria found entombed in
these rocks are truly alive. One approach is to count only those
microbes that can be grown in the laboratory. More than 10 percent of
the cells extracted from sandy sediments where water and nutrients can
generally flow freely will proliferate when given a supply of nutrients in
the laboratory. In contrast, less than one tenth of 1 percent of the cells
drawn from sediments in the arid western U.S. (where the flux of water
is minimal) will grow in a culture dish.....
Paul Krombholz, in cloudy central Mississippi, waiting for the next chance
of rain later today