The marine sulfate reducer Desulfobacterium autotrophicum HRM2 can switch between low and high apparent half-saturation constants for dissimilatory sulfate reduction

Abstract

Studies of the kinetics of dissimilatory sulfate reduction in marine sediment have shown that a mixture of marine sulfate-reducing bacteria (SRB) can reduce sulfate with both a high and low apparent sulfate half-saturation constant (Km). However, all marine pure cultures investigated have shown only low-sulfate affinity sulfate reduction kinetics. It remains unknown whether marine high sulfate-affinity sulfate reduction is catalyzed by unknown SRB or whether known SRB possess unrecognized high-affinity sulfate reduction systems. We used 35S-sulfate incubation experiments to show that cultures of Desulfobacterium autotrophicum HMR2 will switch from low-affinity to high-affinity sulfate reduction when sulfate concentrations fall below 500 μM. The mean Km was 150 μM at high sulfate concentrations and 8 μM at low sulfate concentrations. The high-affinity Km value is comparable to values found in SRB inhabiting freshwater sediments and D. autotrophicum cultures could deplete sulfate to below our detection limit of 25 nM. The switch in Km value was accompanied by a change in the expression of genes encoding membrane-bound transport proteins putatively involved in sulfate uptake in D. autotrophicum. Our results demonstrate that a marine sulfate reducer can efficiently reduce sulfate at both high and low sulfate concentrations, possibly by activation of different sulfate transporters in the membrane.

Depth Distribution and Assembly of Sulfate-Reducing Microbial Communities in Marine Sediments of Aarhus Bay

“…The same pattern is evident when considering the individual OTUs of the various subsurface lineages (Fig. 5), indicating that most SRMs efficiently reduce sulfate at both high and low sulfate concentrations (16,17). However, members of the Desulfobacca lineage (Fig.…”

“…Many SRMs have versatile metabolic strategies (reviewed by Plugge et al [14]) and can, for example, switch between a sulfate-reducing and a sulfate-independent syntrophic or fermentative lifestyle (15). Furthermore, marine SRM communities and some SRM isolates can effectively take up and reduce sulfate at both high and low external sulfate concentrations (16,17), possibly enabling their subsistence in both sulfate-rich and sulfatedepleted parts of marine sediments.…”

Single-Cell Genomics Reveals a Diverse Metabolic Potential of Uncultivated Desulfatiglans-Related Deltaproteobacteria Widely Distributed in Marine Sediment

“…SAG13 and SAG8 also possesses genes coding for homologs of sodium:sulfate transmembrane transporters (DASS family, PF00939), which are also found encoded in the genomes of D. anilini and NaphS2. Notably, a gene expression study suggests that DASS-family transporters function in high-affinity sulfate uptake in the SRM Desulfobacterium autotrophicum ( Tarpgaard et al, 2017 ). SAG5 as well as D. anilini strain NaphS2 also carry a gene encoding a CysZ-family protein (COG2981) ( Supplementary Table S4 ), which also could function in sulfate uptake in SRM ( Marietou et al, 2018 ).…”

Factors controlling the carbon isotope composition of dissolved inorganic carbon and methane in marine porewater: An evaluation by reaction-transport modelling

“…As described in Arndt et al (2006), electron acceptor limitation of organoclastic sulphate reduction was considered by a Monod-term m = [SO 4 2− ] / ([SO 4 2− ] + K S ) with a K S of 1 mM (1.6 mM was used by Boudreau and Westrich, 1984). As it has been recently found that a high-affinity sulphate-reduction may be induced at low sulphate concentrations (K S = 2.6 μM; Tarpgaard et al, 2011Tarpgaard et al, , 2017, the sensitivity of the model results for different half saturation constants was tested. An additional sink of methane and sulphate and source of DIC in Eqs.…”