Description of Aliirhizobium terrae sp. nov., A Plant Growth-Promoting Bacterium Isolated from a Maize-Rice Rotation Agriculture Field.

A polyphasic taxonomic approach was used to characterize a novel bacterium, designated strain CC-CFT758 T , isolated from a maize-rice rotation agriculture field in Taiwan. The cells are aerobic, Gram-stain-negative, rod-shaped, positive for catalase and oxidase, and grow at 20-30 °C (optimal 30 ℃), at pH 6.0-8.0 (optimal 8.0), and with 0-4% (w/v) NaCl (optimum, 2-3%). Phylogenetic analysis based on 16S rRNA gene sequencing, the strain CC-CFT758 T belongs to the genus "Aliirhizobium" of the family Rhizobiaceae. The closest known relatives of this strain are "Aliirhizobium wenxiniae" 166 T (with 98.7% similarity), "Aliirhizobium cellulosilyticum" SEMIA 448 T (with 97.9% similarity), and "Aliirhizobium smilacinae" PTYR-5 T (with 97.0% similarity). The genome size was 5.9 Mbp, with a G + C content of 60.6%. Values of digital DNA-DNA hybridization between the strain and closely related species were 29.5% for "Ali. cellulosilyticum", and 23.9% for "Ali. wenxiniae" and "Ali. smilacinae". Strain CC-CFT758 T exhibited the highest orthologous average nucleotide identity (OrthoANI) values with members of the genus "Aliirhizobium", ranging from 80.4 to 81.6% (n = 3). Chemotaxonomical analysis indicated that strain CC-CFT758 T contained C 16:0 , C 16:0 3OH, C 19:0 cyclo ω8c, C 14:0 3OH/iso-C 16:1 I, and C 18:2 ω6,9c/ante C 18:0 as dominant fatty acids, and the major polyamines were putrescine and spermidine. The polar lipids comprised diphosphatidylglycerol, phosphatidylcholin, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, seven unidentified aminolipids, three unidentified phospholipids, and two unidentified polar lipids. Strain CC-CFT758 T exhibited distinct phylogenetic, phenotypic, and chemotaxonomic characteristics, as well as unique results in comparative analysis of 16S rRNA gene sequence, OrthoANI, AAI, dDDH, and phylogenomic placement. Therefore, this strain represents a new species of the genus "Aliirhizobium", for which the name Aliirhizobium terrae sp. nov. is proposed, with the type strain is CC-CFT758 T (= BCRC 81364 T  = JCM 35482 T ).