Biochemical Measurements of Microbial Mass and Activity from Environmental Samples

Accurate measurement of the mass and activities of environmental microbial assemblies requires methods that differ from those of classical microbiology. Using the leaf-litter detrital microflora recovered after incubationin a semitropical estuary, biochemical assays of multiple components can be made which give reasonably similar estimates of microbial mass, using normalization values from bacterial monocultures. The assays involve recovery of adenosine triphosphate, the unique bacterial cell wall mucopeptide component muramic acid, the uniquely prokaryotic endogenous storage material poly-β-hydroxybutyrate, a series of exoesterase activities, and the extractable lipids, primarily the phospholipids and the glycolipids. If the sampling conditions are such that incorporation of radioisotopes into the microflora is possible, these assays become extraordinarily sensitive. If radioisotope usage can be coupled with the purification of particular lipids, it is possible to gain information on the structure and dynamics of the microbial population.