Idiomarina rhizosphaerae sp. nov. isolated from rhizosphere soil of Kalidium cuspidatum, and reclassification of Idiomarina andamanensis as Pseudidiomarina andamanensis comb. nov., and Idiomarina mangrovi as Pseudidiomarina mangrovi comb. nov

Abstract

A Gram-stain-negative, strictly aerobic, gliding motile, non-spore forming, rod-shaped indole-3-acetic acid producing bacterial strain, designated M1R2S28^T, was isolated from the rhizosphere soil of Kalidium cuspidatum, in Tumd Right Banner, Inner Mongolia, China. Strain M1R2S28^T grew at pH 5.0-10.0 (optimum 8.0), 10-45 °C (optimum 37 °C), in the presence of 0-20% (w/v) NaCl (optimum 5%). The phylogenetic trees based on the 16S rRNA gene sequences and the core-genome both revealed that strain M1R2S28^T clustered tightly with Idiomarina loihiensis L2-TR^T, and shared 99.3, 99.2, 98.7, and < 98.7% of the 16S rRNA gene sequence similarities with I. loihiensis L2-TR^T, I. abyssalis KMM 227 ^T, I. ramblicola R22^T, and all the other current type strains. The strain contained ubiquinone-8 (Q-8) as the sole respiratory quinone. Its major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminolipid, an unidentified phospholipid, and three unidentified lipids. Its major fatty acids were iso-C_15:0, iso-C_17:0, and iso-C_17:1 ω9c. The genomic DNA G + C content was 46.8%. The average nucleotide identity based on BLAST (ANIb) and the digital DNA-DNA hybridization (dDDH) values of strain M1R2S28^T to I. loihiensis L2-TR^T, I. ramblicola R22^T, and I. abyssalis KMM 227 ^T were 93.0, 82.9, and 81.8%, and 51.2, 26.0, and 25.0%, respectively. The phylogenetic and physiological results allowed the discrimination of strain M1R2S28^T from its phylogenetic relatives. Idiomarina rhizosphaerae sp. nov. is, therefore, proposed with strain M1R2S28^T (= CGMCC 1.19026 ^T = KCTC 92133 ^T) as the type strain. Additionally, based on the phylogenomic and genomic analysis results, Idiomarina andamanensis and Idiomarina mangrovi were transferred into genus Pseudidiomarina and be named Pseudidiomarina andamanensis comb. nov. and Pseudidiomarina mangrovi comb. nov., respectively.

Keywords: Comparative genomic analysis; Idiomarina; Phylogenetic analysis; Taxonomy.