Sabulicella flocculans sp. nov., a Floc-Forming Bacterium of the Genus Sabulicella Isolated from Activated Sludge

A novel Gram-stain-negative, cocci-to-oval-shaped, non-sporeforming, floc-forming, aerobic bacterial strain DSY-14^T, was isolated from a wastewater treatment plant located in Shenzhen city, China. Growth of strain DSY-14^T was observed at 22-40 °C, pH 6.0-11.0, and in the presences of 0-1% (w/v) NaCl with optimal growth at 28 °C, pH 7.0 and in the absence of NaCl. This strain was positive for amylase and lipase activities. The major respiratory quinone was Q-10. The polar lipid profile contained aminolipid (AL), aminophospholipid (APL), phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG), phospholipid (PL), and aminoglycolipid (AGL). The major fatty acids were Summed features 8 (C_18:1ω7c and/or C_18:1ω6c,65.3%), Summed features 3 (C_16:1ω7c and/or C_16:1ω6c,14.7%), and C_16:0 (8.7%). Strain DSY-14ᵀ shared the highest 16S rRNA gene sequence similarities with Roseococcus microcysteis NIBR12ᵀ (96.1%) and Sabulicella glaciei MDT2-1-1ᵀ (95.8%). Although the similarities to Roseococcus was marginally higher, its taxonomic affiliation was supported by comprehensive phylogenetic and genomic analyses (ANI and dDDH), confirming its placement within the genus Sabulicella. In the phylogenetic trees reconstructed using 16S rRNA gene or based on the whole genomes, strain DSY-14^T formed a distinct species-level branch within the sabulicella clade of the family acetobacteraceae. The whole-genome of strain DSY-14^T consisted of 3.8 Mbp with the G + C content of 74.0%. The values of dDDH and ANI between strain DSY-14^T and its closest phylogenetic neighbour in the genus Sabulicella were 22.8% and 80.7%, respectively, both below the accepted thresholds for species delineation (70.0% for dDDH and 95.0% for ANI). The phylogenetic, genotypic, phenotypic and chemotaxonomic data demonstrate that strain DSY-14^T represents a novel species in the genus Sabulicella within the family Acetobacteraceae of class Alphaproteobacteria, for which the name Sabulicella flocculans sp. nov. is proposed. The type strain is DSY-14^T (= CCTCC AB 2024240^T = KCTC 8839^T).