Resumen de Environmental Stress Determines the Quality of Bacterial Lysate and Its Utilization Efficiency in a Simple Microbial Loop
Dusko Odic, Valentina Turk, David Stopar
Heterotrophic bacteria provide the critical link in the microbial loop by converting dissolved organic matter (DOM) into particulate form. In this study, DOM was prepared from recently isolated estuarine bacterial strain Vibrio sp. (DSM14379) grown at different salinities [0.2%, 0.5%, 3%, 5%, or 10% (w/v)], washed, concentrated, and lysed by autoclaving. The corresponding lysate-containing media were designated LM0.2, LM0.5, LM3, LM5, and LM10. Vibrio sp. cells grown at different salinities had similar C/N/P ratios, but different C/S ratios, different trace element composition, and different 2D gel electrophoresis protein profiles. Pseudoalteromonas sp. (DSM06238) isolated from a similar environment was able to grow on all lysates, and its biomass production was dependent on lysate type. The highest growth rate and biomass production of Pseudoalteromonas sp. at saturation lysate concentrations were observed in LM3. The biomass production at saturation lysate concentrations was about 3-fold higher as compared to LM0.2 and LM10. The initial respiration rate, intracellular adenosine triphosphate (ATP) levels, and 3H-Leu and 3H-TdR incorporation rates were lowest in LM3. On the other hand, in LM0.2 or LM10 lysates the situation was reversed, the growth rates and biomass production were lowest, whereas 3H-Leu and 3H-TdR incorporation, respiration rates, as well as ATP levels, were highest. These results imply uncoupling of catabolism from growth in either high- or low-salinity lysates. The results also suggest that differences in organic carbon quality generated during Vibrio sp. growth at different NaCl concentrations were propagated through the simple microbial loop, which may have important ecological implications for higher trophic levels that depend on microbial grazing.
