Fibrella aquatilis sp. nov., Fibrella rubiginis sp. nov. and Fibrella forsythiae sp. nov., isolated from freshwater, rusty iron and forsythia flower

Abstract

Three novel strains, designated as HMF5036T, HMF5335T and HMF5405T, were isolated from freshwater, rusty iron and forsythia flower, in Yong-in, Republic of Korea, respectively. They were Gram-stain-negative, facultatively anaerobic, non-motile, reddish-pigmented and rod-shaped bacteria. The predominant fatty acids of three strains were C16 : 1  ω5c and summed feature 3 (comprising C16 : 1  ω7c and/or C16 : 1  ω6c). They were found to contain MK-7 as the predominant menaquinone. The major polar lipids are phosphatidylethanolamine, an unidentified aminophospholipid and an unidentified lipid. Strains HMF5036T, HMF5335T and HMF5405T exhibited the highest 16S rRNA gene sequence similarities of 91.8, 92.6 and 93.6 % to Fibrella aestuarina BUZ 2T and less than 88.7 % to other members of the family Spirosomaceae . Similarity values among the three isolates ranged from 94.9 to 96.6 %. Phylogenetic analysis based on the 16S rRNA gene sequences of the three isolates revealed that they formed a distinct clade within the family Spirosomaceae . The genome sizes of strains HMF5036T, HMF5335T and HMF5405T were 6.8, 6.4 and 7.8 Mbp, and their DNA G+C contents were 54.9, 54.0 and 52.1 mol%, respectively. The average nucleotide identity, digital DNA–DNA hybridization and amino acid identity values between three isolates and F. aestuarina BUZ 2T were 73.8–82.2, 19.6–25.4 and 75.0–87.5 %, respectively. These values were lower than the recommended threshold values for species delimitation. Based on the results of the phenotypic, genotypic, chemotaxonomic and phylogenetic investigations, three novel species, Fibrella aquatilis sp. nov., Fibrella rubiginis sp. nov. and Fibrella forsythiae sp. nov. are proposed. The type strains are HMF5036T (=KCTC 82476T=NBRC 115092T), HMF5335T (=KCTC 82477T=NBRC 115093T) and HMF5405T (=KCTC 82478T=NBRC 115094T), respectively.