Environmental Stress Determines the Quality of Bacterial Lysate and Its Utilization Efficiency in a Simple Microbial Loop

Abstract

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 LM(0.2), LM(0.5), LM(3), LM(5), and LM(10). 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 LM(3). The biomass production at saturation lysate concentrations was about 3-fold higher as compared to LM(0.2) and LM(10). The initial respiration rate, intracellular adenosine triphosphate (ATP) levels, and (3)H-Leu and (3)H-TdR incorporation rates were lowest in LM(3). On the other hand, in LM(0.2) or LM(10) lysates the situation was reversed, the growth rates and biomass production were lowest, whereas (3)H-Leu and (3)H-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.

Salinity and Temperature Effects on Physiological Responses of Vibrio fischeri from Diverse Ecological Niches

“…For instance, stress is known to affect the quality of organic carbon produced by vibrios living in simple, microbial loop foodwebs. This phenomenon influences the quality of carbon available to other trophic levels [53]. Illumination in recent years that the multitude of microbial physiological responses to stress (e.g., heat shock, starvation) are coupled and cross-talk elevates the complexity and provides fertile ground for intriguing research [54].…”

Conditioning of the membrane fatty acid profile of Escherichia coli during periodic temperature cycling

“…Bacterial respiration was measured with a Hewlett Packard 5890 gas chromatograph equipped with a thermal conductivity detector as described previously (Odić et al, 2007). Typically, a 0.25 ml gas sample was taken every 30-60 min during incubation using a 1 ml syringe with a hypodermic needle.…”

“…The data were corrected for different amounts of CO 2 dissolved in the liquid phase at different temperatures. Intracellular content of ATP was measured with an ATP-dependent luciferin-luciferase system as described previously (Odić et al, 2007).…”

Viscosity dictates metabolic activity of Vibrio ruber

“…Respiration rate was determined as described previously (Odić et al, 2007; Danevčič and Stopar, 2011). Briefly, 5 mL of bacterial culture was centrifuged for 15 min at 14,972 g and 4°C.…”

“…The ratio between the gas and liquid phase was 2:1 (V/V). The amount of released CO 2 was measured on a gas chromatograph with thermal conductivity detector (TCD) at the beginning and after one hour of incubation at 28°C and 150 rpm (Odić et al, 2007). Control samples contained 5 mL of 3% (w/V) NaCl solution.…”