RNA synthesis as a measure of microbial growth in aquatic environments. II. Field applications

Abstract

Rates of stable ribonucleic acid (RNA) synthesis have been calculated from time-series measurements of the uptake of ³H-adenine and labeling of the intracellular adenosine triphosphate (ATP) and stable RNA pools for microbial communities from a variety of freshwater and marine ecosystems. Total rates of microbial RNA synthesis ranged from 6.6 pmol to 3.8x10⁵ pmol of adenine incorporated into RNA l⁻¹ h⁻¹. Most of the variation was attributable to differences in microbial biomass; if total rate data are normalized to living microbial carbon (based on ATP measurements), the variation in specific rates of RNA synthesis is decreased by a factor of 100 to 1 000 for microbial communities from diverse environments. Light/dark experiments indicated that the uptake and incorporation of ³H-adenine are uncoupled from photophosphorylation. The measurement of rates of stable RNA synthesis of microbial assemblages in nature can yield useful information concerning in situ growth rates and the response of communities to changes in environmental conditions such as nutrient additions.