| Abstract |
Two Gram-stain-negative and rod-shaped bacteria, designated as RZ5T and RZ22T, isolated from a red macroalgae sample, were characterized by a polyphasic approach to clarify their taxonomic position. Strain RZ5T grew at 4-33 °C (optimum, 25-28 °C), pH 6.5-8.5 (optimum, 7.0-8.0) and in 0.5-5.0% (w/v) NaCl (optimum, 1.0%). Strain RZ22T grew at 4-28 °C (optimum, 20-25 °C), pH 6.5-8.5 (optimum, 7.0-8.0) and in 2.0-5.0% (w/v) NaCl (optimum, 3.0%). Strain RZ5T possessed a flagellum and was motile, while strain RZ22T lacked a flagellum and was non-motile. Phylogenetic analysis based on 16S rRNA gene sequences indicated that both isolates belonged to the genus Psychromonas and were most closely related to Psychromonas aquatilis M1A1T (98.1%) and Psychromonas antarctica DSM 10704T (97.1%) for strains RZ5T and RZ22T, respectively. The predominant fatty acids of both strains were C16 : 0 and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). The major polar lipids for strain RZ5T comprised phosphatidylethanolamine (PE) and glycolipids (GLs), while those for strain RZ22T comprised PE, diphosphatidylglycerol and GLs. The average nt identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strains RZ5T and RZ22T were 85.4% and 18.9%, respectively. Strain RZ5T had ANI values of 84.3-85.5% and dDDH values of 18.3-21.3% to members of the genus Psychromonas. Strain RZ22T had ANI values of 84.2-85.2% and dDDH values of 18.4-22.1% to members of the genus Psychromonas. The G+C content of the genomic DNA of strains RZ5T and RZ22T was 36.7 mol% and 35.6 mol%, respectively. Strains RZ5T and RZ22T possessed ubiquinone-8 as the sole respiratory quinone. The phylogenetic analyses and genomic comparisons, combined with phenotypic and chemotaxonomic features, strongly supported that the two strains should be classified as representing two novel species of the genus Psychromonas, for which we propose the names Psychromonas algicola sp. nov. (type strain RZ5T=JCM 33153T=MCCC 1H00360T) and Psychromonas algarum sp. nov. (type strain RZ22T=JCM 33154T=MCCC 1H00361T).
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