Sulfate-Reducing Bacteria from the Arabian Sea—Their Distribution in Relation to Thiosulfate-Oxidizing and Heterotrophic Bacteria

Examination of water and sediment samples collected off the west coast of India and atolls of Lakshadweep Archipelago showed that the sulfate-reducing bacteria (SRB) occur not only in the bottom sediments but also in apparently aerobic surface waters and beach sediments. The abundance ranged from non-detectable levels to 0.5˙10² ˙ml⁻¹ in water and from 0.1–94˙10²˙g⁻¹ dry sediment. Physiological tests of SRB isolates showed that these waters harbored not only lactate but also propionate and acetate utilizers. Over 50% of the isolates showed growth with formate. Tests showed affinities to Desulfovibrio, and Desulfotomaculum which comprised 20 and 29% of the isolates respectively. The others viz. Desulfobulbus, Desulfobacter and Desulfococcus together comprised about 42%. Simultaneous examinations of aerobic and anaerobic Thiobacilli-like organisms [TLOa and TLOan respectively] and culturable heterotrophic aerobic and anaerobic bacteria (AB and AnB respectively) showed that SRB were significantly correlated to TLOan (r = 0.6760, P < 0.001), and to AnB (r = 0.6649, P < 0.001).