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