ABSTRACT
Populations, cell size, DNA, and biomass-distributiotis of pelagic bacteria can be obtained by flow cytometry from event frequency, forward scatter and fluorescence intensity of cells stained with 4'6-diamidino-2-phenylindole (DAPI). Anticipated uses include evaluating organism activity from simultaneous analysis of cell size, DNA content, and RNA content and evaluating growth and selective predation rates from rates of change of bacterial populations and their size distributions in systems of limited and controlled populations of predators. Essential to the analysis of aquatic bacteria is good laser performance, clean optics, a well-aligned optical path, and stable sample flow. Although instrument alignment is performed with linear scaling, logarithmic amplification is used for bacterial analyses to give a multidecade dynamic range. Cell volume is obtained from a standard curve prepared using various bacteria sized by Coulter counter; it relates forward scatter intensity to Coulter cell volume.
