ABSTRACT
Bacterial production or cell concentration often needs to be presented in carbon (C) or nitrogen (N) biomass. For field applications, bacterial biomass is routinely estimated from cell concentrations or cell volumes (biovolume) with appropriate conversion factors. For the direct determination of a conversion factor, in principle, three independent parameters are measured: number of cells, biovolume of the cells, and biomass. A method combines the acridine orange (AO) direct count (DC) method for cell enumeration, AO epifluorescence photomicrography for the biovolume measurement, and CHN analysis for C and N biomass. For example, bacterial cells are derived from natural seawater and grown in unsupplemented, filter-sterilized, partie le-free natural seawater; corrections are made for the bacterial cells passing through glass fiber GF/F filters; and biovolume measurement is calibrated with fluorescent microspheres of known diameters. Use of per-cell biomass conversion factors, being free of the bias due to biovolume measurements, would be more practical for natural planktonic bacteria.
