Phylogeny and Metabolic Potential of New Giant Sulfur Bacteria of the Family Beggiatoaceae from Coastal-Marine Sulfur Mats of the White Sea.

The family Beggiatoaceae is currently represented by 25 genera in the Genome Taxonomy Database, of which only 6 have a definite taxonomic status. Two metagenome-assembled genomes (MAGs), WS_Bin1 and WS_Bin3, were assembled from metagenomes of the sulfur mats coating laminaria remnants in the White Sea. Using the obtained MAGs, we first applied phylogenetic analysis based on whole-genome sequences to address the systematics of Beggiatoaceae , which clarify the taxonomy of this family. According to the average nucleotide identity (ANI) and average amino acid identity (AAI) values, MAG WS_Bin3 was assigned to a new genus and a new species in the family Beggiatoaceae , namely, ' Candidatus Albibeggiatoa psychrophila' gen. nov., sp. nov., thus providing the revised taxonomic status of the candidate genus 'BB20'. Analysis of 16S rRNA gene homology allowed us to identify MAG WS_Bin1 as the only currently described species of the genus ' Candidatus Parabeggiatoa', namely, ' Candidatus Parabeggiatoa communis', and consequently assign the candidate genus 'UBA10656', including four new species, to the genus ' Ca . Parabeggiatoa'. Using comparative whole-genome analysis of the members of the genera ' Candidatus Albibeggiatoa' and ' Ca . Parabeggiatoa', we expanded information on the central pathways of carbon, sulfur and nitrogen metabolism in the family Beggiatoaceae .