Ensifer alkalisoli sp. nov. isolated from root nodules of Sesbania cannabina grown in saline–alkaline soils

Abstract

A group of Sesbania cannabina rhizobia belonging to four recA genotypes of a novel group was further characterized in comparison with the related Ensifer species. They showed 98.2 to 99.9 % similarities among themselves and 92.9 to 93.3 % similarities with the most related strain Ensifer sojae CCBAU 05684T in multilocus sequence analysis of recA, atpD and glnII. The genome average nucleotide identity values between representative strain YIC4027T and the type strains of its closely related species were 81.6 to 88.9 %. Identical symbiotic gene (nodA, nodC and nifH) sequences highly similar with those in other Sesbania-nodulating strains (Rhizobium sp. SIN-1, Neorhizobium huautlense S02T, Ensifer saheli ORS609T and Rhizobium sp. IRBG74) were detected. The representative strain YIC4027T could form effective nodules on its original host Sesbaniacannabina, but not on Sophora flavescens, Trifolium repens, Glycine max, Glycyrrhiza uralensis, Phaseolus vulgaris or Medicago sativa. The use of lactulose as sole carbon source, possession of C13 : 0 2-OH, C13 : 1 at 12-13, C15 : 1 iso ω9c, C17 : 0 anteiso and C18 : 0 iso and absence of C14 : 0 anteiso, C15 : 0 anteiso and C18 : 0 3-OH in fatty acids distinguished the strain YIC4027T from the type strains of its closely related species. Based on all the analyses mentioned above, we propose a novel species Ensifer alkalisoli sp. nov. and designate YIC4027T (=HAMBI 3655T=LMG 29286T) as the type strain. The genome size of YIC4027T is 5.97 Mbp, comprising 5588 predicted genes, and the DNA G+C content is 62.2 mol%.