Limnobacter thiooxidans gen. nov., sp nov., a novel thiosulfate-oxidizing bacterium isolated from freshwater lake sediment

Two novel thiosulfate-oxidizing strains were isolated from sediment of the littoral zone of a freshwater lake (Lake Chiemsee, Bavaria. Germany). The n ew isolates, designated CS-K1 and CS-K2(T), were Gram-negative, slightly cu rved rods with pointed ends that were motile by means of single polar flage lla. Both strains were obligately aerobic and grew on a variety of organic substrates, but not autotrophically. The utilization of thiosulfate led to an increase in the growth yield, indicating that these strains were able to grow chemolithoheterotrophically by oxidation of thiosulfate to sulfate. T he optimum thiosulfate concentrations for growth were determined to be 10 m M for strain CS-K1 and 20 mM for strain CS-K2T. Phylogenetically, both stra ins were affiliated to the beta -Proteobacteria. Their characterization by a polyphasic approach resulted in the placement of both strains into a sing le species that is related only distantly to any known type species. Thus, the creation of a novel taxon is proposed, with the name Limnobacter thioox idans gen, nov., sp, nov., to include the novel strains. In addition, the p hylogenetic position of the chemolithoheterotrophic strain 'Thiobacillus' Q was determined.