Marine Heterotrophic Bacteria in Continuous Culture, the Bacterial Carbon Growth Efficiency, and Mineralization at Excess Substrate and Different Temperatures

To model the physiological potential of marine heterotrophic bacteria, their role in the food web, and in the biogeochemical carbon cycle, we need to know their growth efficiency response within a matrix of different temperatures and degrees of organic substrate limitation. In this work, we present one part of this matrix, the carbon growth efficiencies of marine bacteria under different temperatures and nonlimiting organic and inorganic substrate supply. We ran aerobic turbidostats with glucose enriched seawater, inoculated with natural populations of heterotrophic marine bacteria at 10, 14, 18, 22, and 26°C. The average cell-specific growth rates increased with temperature from 1.17 to 2.6 h−1. At steady-state total CO2 production, biomass production [particulate organic carbon (POC) and nitrogen (PON)], and viruslike particle abundance was measured. CO2 production and specific growth rate increased with increasing temperature. Bacterial carbon growth efficiency (BCGE), the particulate carbon produced per dissolved carbon utilized, varied between 0.12 and 0.70. Maximum BCGE values and decreased specific respiration rates occurred at higher temperatures (22 and 26°C) and growth rates. This trend was largely attributable to an increase in POC per cell abundance; when the BCGE was recalculated, parameterizing the biomass as the product of cell concentration and a constant cellular carbon content, the opposite trend was observed.