Trial of direct diagnosis of Bradyrhizobium japonicum and B. elkanii from soils by fatty acid analysis based on plant bait technique

Previous studies have already reported that cellular fatty acid analysis is a useful taxonomic tool for classifying and identifying Bradyrhizobium strains, including B. japonicum, B. elkanii and Bradyrhizobium sp. obtained from mungbean. In this study, the existence of species-specific fatty acids, 16:1ω5cis, 17:0 cyclo and 19:0 cyclo ω8cis were remarked as the identification profiles within B. japonicum and B. elkanii. Direct detection of B. japonicum and B. elkanii from plant grown soils were performed by whole cellular fatty acid analysis combined with plant baiting technique. Tested plant materials, soybean, mungbean, groundnut and cowpea were used as the plant baiting experiment. Soil materials, contaminated soils to single strain and mixture of B. japonicum and B. elkanii, and natural infested soils were prepared for whole cellular fatty acid analysis. Bacteria trap experiment with plant baiting technique revealed that whole cellular fatty acid analysis was effectively detected B. japonicum and B. elkanii from all soil materials by using soybean plant.