Genome Sequence and Phylogenetic Analysis of the Sulfide-Oxidizing Heliobacterium “Heliomicrobium sulfidophilum” Strain BR4

Heliobacteraceae are unique endospore-forming photosynthetic bacteria that are known for possessing the simplest photosynthetic apparatus of any known organism. More genomic and physiological analysis is needed to further understand the evolution of photosynthesis and the unique metabolic pathways of nitrogen and sulfur metabolism in this family. Here, we present the genome and phylogenetic analysis of “Heliomicrobium sulfidophilum” strain BR4T, which was isolated previously from an alkaline sulfide-containing hot spring. In addition to the presence of a Type I reaction center, genes for bacteriochlorophyll g synthesis and nitrogenase system, the genomic analysis also explains the need for biotin as a supplied growth factor in Heliomicrobium species. The Heliobacteriaceae genome comparison also revealed a previously unidentified gene cluster of heterodisulfide reductase-like proteins (Hdr genes) and molybdopterin-based enzymes for polysulfide reductase. The whole-genome comparison, including ANI, dDDH, and single-gene phylogenetic analyses, confirms the correct placement of strain BR4 in the Heliomicrobium genus and strengthens the overall phylogenetic distribution of the Heliobacteriaceae.