Community size and metabolic rates of psychrophilic sulfate-reducing bacteria in Arctic marine sediments

The numbers of sulfate reducers in two Arctic sediments within situ tempera tures of 2.6 and -1.7 degrees C were determined. Most-probable-number count s were higher at 10 degrees C than at 20 degrees C, indicating the predomin ance of a psychrophilic community. Mean specific sulfate reduction rates of 19 isolated psychrophiles were compared to corresponding rates of 9 marine , mesophilic sulfate-reducing bacteria. The results indicate that, as a phy siological adaptation to the permanently cold Arctic environment, psychroph ilic sulfate reducers have considerably higher specific metabolic rates tha n their mesophilic counterparts at similarly low temperatures.