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

Abstract

The numbers of sulfate reducers in two Arctic sediments with in situ temperatures of 2.6 and -1.7 degrees C were determined. Most-probable-number counts were higher at 10 degrees C than at 20 degrees C, indicating the predominance 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 physiological adaptation to the permanently cold Arctic environment, psychrophilic sulfate reducers have considerably higher specific metabolic rates than their mesophilic counterparts at similarly low temperatures.

FIG. 1

Depth profile of SRRs in Hornsund (a) and Storfjord (c) at in situ temperatures and MPN counts of SRB in Hornsund (b) and Storfjord (d) sediments. MPN series were incubated at different temperatures with either lactate (, 20°C; ▨, 10°C; ▧, 4°C) or acetate (□, 20°C; ▧, 10°C; ⊞, 4°C). Horizontal bars represent 95% confidence intervals, and vertical bars indicate the depths of sediments used for MPN enrichments.

FIG. 2

Mean values of specific SRRs of 10 mesophilic sulfate reducers (closed circles) determined at 4, 8, and 13°C, 14 psychrophiles from Hornsund sediments (open square), and 5 psychrophiles from Storfjord sediments (open triangle). Dashed line represents the Arrhenius fit of specific SRRs for mesophiles. Bars represent standard deviations of the means for all strains.