Physiological response to temperature changes of the marine, sulfate-reducing bacterium Desulfobacterium autotrophicum

Abstract

The physiological response of bacteria to temperature is critical for the regulation of biogeochemical processes on daily, seasonal, and inter-annual time scales. We investigated the temperature response of the marine sulfate-reducing bacterium Desulfobacterium autotrophicum strain HRM2. Growth experiments in a temperature gradient block demonstrated that D. autotrophicum is psychrotolerant and grows between 0 and 31°C. The normal range of temperature for growth is between 4 and 29°C. The physiological response to temperature changes was studied with three sets of cells that were acclimated at 4, 10, and 28°C, respectively. Sulfate reduction rates were determined in the temperature gradient block with short-term incubations to minimize growth. The rates were similar at the 4 and 10°C acclimation temperature, and exhibited an enhanced response at 28°C. At every acclimation temperature, sulfate reduction rates increased 20-fold from −1.7 to 41°C. The relative proportion of cellular unsaturated fatty acids (e.g. cis16:1) and short-chain fatty acids increased when cells were grown at 4°C compared to 28°C. The proteome of D. autotrophicum strain HRM2 was studied by two-dimensional gel electrophoresis with soluble extracts of cells grown at the three respective acclimation temperatures. Protein patterns were similar with the exception of two proteins showing 5–10-fold lower abundance in the 4°C culture compared to the 28°C culture. In general, D. autotrophicum strain HRM2 responded to low temperatures by reduced metabolic activity rather than by pronounced de novo synthesis of specifically adapted enzymes. Such a strategy agrees well with in situ activities measured in field studies and may reflect a common physiological principle of psychrotolerant marine sulfate-reducing bacteria.