Symbiotic Growth of a Thermophilic Sulfide-Oxidizing Photoautotroph and an Elemental Sulfur-Disproportionating Chemolithoautotroph and Cooperative Dissimilatory Oxidation of Sulfide to Sulfate

• Published in: Frontiers in microbiology Vol. 10; p. 1150
• Main Authors: Kawai, Shigeru, Kamiya, Naoki, Matsuura, Katsumi, Haruta, Shin
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 24.05.2019
• Subjects: anoxygenic photosynthesis; elemental sulfur; hot spring microbial mats; Microbiology; sulfide; sulfur-disproportionation; hot spring microbial mats; sulfide; sulfur-disproportionation; elemental sulfur; anoxygenic photosynthesis
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2019.01150

A thermophilic filamentous anoxygenic photosynthetic bacterium, , is widely distributed in neutral to slightly alkaline hot springs. Sulfide has been suggested as an electron donor for autotrophic growth in microbial mats dominated with , but remarkable photoautotrophic growth of isolated has not been observed with sulfide as the sole electron source. From the idea that sulfide is oxidized to elemental sulfur by and the accumulation of elemental sulfur may have an inhibitory effect for the growth, the effects of an elemental sulfur-disproportionating bacterium that consumes elemental sulfur was examined on the autotrophic growth of , strain NA9-6, isolated from Nakabusa hot spring. A sulfur-disproportionating bacterium, strain TF1, also isolated from Nakabusa hot spring was co-cultured with and were successfully co-cultured in a medium containing thiosulfate as the sole electron source and bicarbonate as the sole carbon source. Quantitative conversion of thiosulfate to sulfate and a small transient accumulation of sulfide was observed in the co-culture. Then the electron source of the established co-culture was changed from thiosulfate to sulfide, and the growth of and was successfully observed with sulfide as the sole electron donor for the autotrophic growth of the co-culture. During the cultivation in the light, simultaneous consumption and accumulation of sulfide and sulfate, respectively, were observed, accompanied with the increase of cellular DNAs of both species. likely works as an elemental sulfur scavenger for , and seems to work as a sulfide scavenger for . These results suggest that grows autotrophically with sulfide as the electron donor in the co-culture with , and the consumption of elemental sulfur by enabled the continuous growth of the in the symbiotic system. This study shows a novel symbiotic relationship between a sulfide-oxidizing photoautotroph and an elemental sulfur-disproportionating chemolithoautotroph via cooperative dissimilatory sulfide oxidation to sulfate.