biostudies-literatureMarietou AEuropean Research Council200-210https://www.ebi.ac.uk/biostudies/studies/S-EPMC8692349biostudies-literatureUnknown16(1)Sulfate-reducing microorganisms (SRM) in subsurface sediments live under constant substrate and energy limitation, yet little is known about how they adapt to this mode of life. We combined controlled chemostat cultivation and transcriptomics to examine how the marine sulfate reducer, Desulfobacterium autotrophicum, copes with substrate (sulfate or lactate) limitation. The half-saturation uptake constant (K<sub>m</sub>) for lactate was 1.2 µM, which is the first value reported for a marine SRM, while the K<sub>m</sub> for sulfate was 3 µM. The measured residual lactate concentration in our experiments matched values observed in situ in marine sediments, supporting a key role of SRM in the control of lactate concentrations. Lactate limitation resulted in complete lactate oxidation via the WThe ISME journalResponse to substrate limitation by a marine sulfate-reducing bacterium.PMC8692349294200Glombitza CJorgensen BBMarietou AKjeldsen KUfalseResponse to substrate limitation by a marine sulfate-reducing bacterium.Sulfate-reducing microorganisms (SRM) in subsurface sediments live under constant substrate and energy limitation, yet little is known about how they adapt to this mode of life. We combined controlled chemostat cultivation and transcriptomics to examine how the marine sulfate reducer, Desulfobacterium autotrophicum, copes with substrate (sulfate or lactate) limitation. The half-saturation uptake constant (K<sub>m</sub>) for lactate was 1.2 µM, which is the first value reported for a marine SRM, while the K<sub>m</sub> for sulfate was 3 µM. The measured residual lactate concentration in our experiments matched values observed in situ in marine sediments, supporting a key role of SRM in the control of lactate concentrations. Lactate limitation resulted in complete lactate oxidation via the W2022-01-01T00:00:00Z2022 Jan2026-05-08T19:57:06.591Z2025-02-19T03:26:26.182ZS-EPMC86923493428536510.1038/s41396-021-01061-2