Sphingomonas chlorellae sp. nov., Isolated from Outdoor Photobioreactor Culturing Chlorella sp. HS2 with Soy Sauce...

Two yellow-pigmented bacterial strains, designated Y1Aᵀ and Y6, were isolated from an outdoor bioreactor cultivating Chlorella sp. HS2 with soy sauce wastewater as the nutrient source. Phylogenetic analysis based on the nearly complete 16S rRNA gene sequence showed that Y1Aᵀ shared highest similarity with S. tabacisoli CGMCC 1.16275^T (96.9%), followed by Sphingomonas changnyeongensis C33ᵀ (96.75%) and S. changbaiensis NBRC 104936^T (96.38%). Genome sequencing revealed that strain Y1Aᵀ comprises 3.67 Mb with a DNA G + C content of 68.56% and 3,346 predicted genes, while strain Y6 exhibited a highly similar genome (3.67 Mb, 68.60%, 3,341 genes). ANI (99.97%) and dDDH (100%) values confirmed that Y1Aᵀ and Y6 belong to the same taxon. However, ANI (72.06-78.43%) and dDDH (19.2-22.1%) values with closest relatives were below species thresholds, supporting the recognition of a novel species. API ZYM revealed overlapping enzyme profiles between the two novel strains; however, both Y1Aᵀ and Y6 could be distinguished from most related taxa by the presence of α-galactosidase and the absence of α-chymotrypsin activities. Moreover, Y6 was uniquely positive for cystine arylamidase but lacked trypsin activity. Major fatty acid was summed feature 8 (C_18:1 ω7c/ω6c). Polar lipids included phosphatidylethanolamine, phosphatidylglycerol, aminophospholipids, and unidentified aminolipids, and the major respiratory quinone was ubiquinone Q-10. Based on phylogenetic, genomic, phenotypic, chemotaxonomic, and polyamine analyses, strains Y1Aᵀ and Y6 represent a novel species of the genus Sphingomonas, for which the name Sphingomonas chlorellae sp. nov. is proposed. The type strain is Y1Aᵀ (= KCTC 18312ᵀ =LMG 34185ᵀ).