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Appl. Environ. Microbiol., Jul 1996, 2411-2415, Vol 62, No. 7
J Shen and R Bartha
Biodegradability screening tests of soil commonly measure 14CO2 evolution
from radiolabeled test compounds, and glucose has often served as a
positive control. When constant amounts of radiolabel were added to soil in
combination with increasing amounts of unlabeled substrates, glucose and
some related hexoses behaved in an anomalous manner. In contrast to that of
formate, benzoate, n-hexadecane, or bis(2-ethylhexyl) phthalate, dilution
of glucose radiocarbon with unlabeled glucose increased rather than
decreased the rate and extent of 14CO2 evolution. [14C]glucose
incorporation into biomass and Vmax values were consistent with the
interpretation that application of relatively high concentrations of
glucose to soil shifts the balance of the soil microbial community from the
autochthonous (humus-degrading) to the zymogeneous (opportunistic) segment.
The higher growth and turnover rates that define zymogeneous
microorganisms, combined with a lower level of carbon incorporation into
their biomass, result in the evolution of disproportionate percentages of
14CO2. When used as positive controls, glucose and related hexoses may
raise the expectations for percent 14CO2 evolution to levels that are not
realistic for other biodegradable compounds.
Copyright © 1996, American Society for Microbiology
Metabolic efficiency and turnover of soil microbial communities in biodegradation tests
Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231, USA.
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