Analysis of cellular fatty acids and phenotypic relationships of Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium species using the Sherlock microbial identification system

Previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. In this study, the fatty acid profiles of over 600 strains belonging to the genera #Agrobacterium$, #Bradyrhizobium$, #Mesorhizobium$, #Rhizobium$ and #Sinorhizobium$ were evaluated using the gas-chromatography-based Sherlock Microbial Identification System (MIS). Data collected with the MIS showed that the three phylogenetically defined biovars of the genus #Agrobacterium$ formed discrete clusters, whilst species belonging to the genus #Mesorhizobium$ formed three subclusters which were easily distinguished. These three subclusters contained #Mesorhizobium ciceri$ and #Mesorhizobium mediterraneum$,#Mesorhizobium tianshanense$ fatty acid group I and #Mesorhizobium plurifarium$, and #Mesorhizobium Huakuii$ and #Mesorhizobium loti$. The genus #Sinorhizobium$ was composed of an individual position for #Sinorhizobium meliloti$ and a large cluster comprising #Sinorhizobium fredii$, #Sinorhizobium saheli$, #Sinorhizobium terangae$, #Sinorhizobium kostiense$ and #Sinorhizobium arboris$. #S. meliloti$ contained significantly higher levels of the fatty acid 19 : 0 cyclo omega8cis and clustered with #Rhizobium$ sp. (#Hedysarum coronarium$). However, discrimination between the species of genera #Sinorhizobium$ and #Rhizobium$ was a function of the concentration of 16 : 0 3-OH. The genus #Rhizobium$ contained a single cluster containing #Rhizobium$ sp. (#Hedysarum coronarium$), #Rhizobium gallicum$, #Rhizobium leguminosarum$ and #Rhizobium etli$, along with individual positions for #Rhizobium giardinii$, #Rhizobium tropici$, #Rhizobium galegae$ and #Rhizobium hainanense$. #R. tropici$ and #R. hainanense$ exhibited similarity to #Agrobacterium biovar$ 2, whilst #R. galegae$ was similar to #Agrobacterium biovar$ 1... (D'après résumé d'auteur