Psychromonas algicola sp. nov. and Psychromonas algarum sp. nov., two novel bacteria isolated from red macroalgae...

Two Gram-stain-negative and rod-shaped bacteria, designated as RZ5^T and RZ22^T, isolated from a red macroalgae sample, were characterized by a polyphasic approach to clarify their taxonomic position. Strain RZ5^T 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 RZ22^T 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 RZ5^T possessed a flagellum and was motile, while strain RZ22^T 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 M1A1^T (98.1%) and Psychromonas antarctica DSM 10704^T (97.1%) for strains RZ5^T and RZ22^T, respectively. The predominant fatty acids of both strains were C_16 : 0 and summed feature 3 (C_16 : 1  ω7c/C_16 : 1  ω6c). The major polar lipids for strain RZ5^T comprised phosphatidylethanolamine (PE) and glycolipids (GLs), while those for strain RZ22^T comprised PE, diphosphatidylglycerol and GLs. The average nt identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strains RZ5^T and RZ22^T were 85.4% and 18.9%, respectively. Strain RZ5^T had ANI values of 84.3-85.5% and dDDH values of 18.3-21.3% to members of the genus Psychromonas. Strain RZ22^T 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 RZ5^T and RZ22^T was 36.7 mol% and 35.6 mol%, respectively. Strains RZ5^T and RZ22^T 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 RZ5^T=JCM 33153^T=MCCC 1H00360^T) and Psychromonas algarum sp. nov. (type strain RZ22^T=JCM 33154^T=MCCC 1H00361^T).