Microbial biomass can
also be measured by determination of specific cell biochemical constituents
such as ATP, DNA, RNA, proteins, phospholipids, bacterial cell wall components,
or photosynthetic pigments (Sutton, 2002).
a.
ATP
Adenosine triphosphate
has often been used to determine live microbial biomass in environmental
samples, using a ratio of C/ATP
= 250 for aquatic
samples. However, the ATP content of cells varies with the growth rate and
metabolic state of microorganisms and nutrient limitation. A better measure is
the total
adenylate pool AT
(AT = ATP + ADP + AMP) because it does
not change greatly with changes in metabolic activities of the microorganisms.
The adenylate
energy charge (EC)
ratio provides information on growth potential of naturally occurring microbial
populations.
