Mangrovibacter plantisponsor gen. nov., sp. nov., a nitrogen-fixing bacterium isolated from a mangrove-associated wild rice (Porteresia coarctata Tateoka)

Abstract

A facultatively anaerobic, nitrogen-fixing bacterium, strain MSSRF40T, was isolated from roots of mangrove-associated wild rice (Porteresia coarctata Tateoka). On the basis of 16S rRNA gene sequence similarities, strain MSSRF40T was shown to belong to the family Enterobacteriaceae, most closely related to Cronobacter muytjensii E603T (97.2 % sequence similarity), Enterobacter cloacae subsp. dissolvens LMG 2683T (97.1 %), E. radicincitans D5/23T (97.1 %) and E. ludwigii EN-119T (97.0 %). Sequence analysis of rpoB, gyrB and hsp60 genes showed that strain MSSRF40T had relatively low sequence similarity (<91, <84 and <90 %) to recognized species of different genera of the family Enterobacteriaceae and formed an independent phyletic lineage in all phylogenetic analyses using the 16S rRNA, rpoB, gyrB and hsp60 genes, clearly indicating that strain MSSRF40T could not be affiliated to any of the recognized genera within the family Enterobacteriaceae. The dominant cellular fatty acids were C16 : 0, C16 : 1 ω7c and/or iso-C15 : 0 2-OH and C18 : 1 ω7c, similar to those of other members of the Enterobacteriaceae. The DNA G+C content was 50.1 mol%. Phylogenetic distinctiveness and phenotypic differences from its phylogenetic neighbours indicated that strain MSSRF40T represents a novel species and genus within the family Enterobacteriaceae, for which the name Mangrovibacter plantisponsor gen. nov., sp. nov. is proposed. The type strain of Mangrovibacter plantisponsor is strain MSSRF40T (=LMG 24236T =DSM 19579T).