Complete Genome Sequence of the Plant Growth-Promoting BacteriumHartmannibacter diazotrophicusStrain E19T

Abstract

Strain E19Tdescribed asHartmannibacter diazotrophicusgen. nov. sp. nov. was isolated from the rhizosphere ofPlantago winterifrom a natural salt meadow in a nature protection area. Strain E19Tis a plant growth-promoting rhizobacterium able to colonize the rhizosphere of barley and to promote its growth only under salt stress conditions. To gain insights into the genetic bases of plant growth promotion and its lifestyle at the rhizosphere under salty conditions, we determined the complete genome sequence using two complementary sequencing platforms (Ilumina MiSeq and PacBioRSII). The E19Tgenome comprises one circular chromosome and one plasmid containing several genes involved in salt adaptation and genes related to plant growth-promoting traits under salt stress. Based on previous experiments, ACC deaminase activity was identified as a main mechanism of E19Tto promote plant growth under salt stress. Interestingly, no genes classically reported to encode for ACC deaminase activity are present. In general, the E19Tgenome provides information to confirm, discover, and better understand many of its previously evaluated traits involved in plant growth promotion under salt stress. Furthermore, the complete E19Tgenome sequence helps to define its previously reported unclear 16S rRNA gene-based phylogenetic affiliation.Hartmannibacterforms a distinct subcluster with generaMethylobrevis,Pleomorphomonas,Oharaeibacter, andMongoliimonassubclustered with genera belonging toRhizobiales.