Study of Acid Tolerance of Sinorhizobium meliloti

In this experiment,after separating and screening rhizobium from the root nodules of Medicago sativa L.growing on an acidy soil,three rhizobium strains which grew well on YMA medium of pH 4.8 were obtained.They were then back-inoculated and their growth curves were determined.The results indicated that strain 91532 showed higher acid tolerance than the other two strains in this study and the rhizobium strains nodulating Medicago sativa L.reported in previous literature.16SrRNA sequencing analysis and cell scanning electron microscope photographs showed that strain 91532 belongs to Sinorhizobium meliloti.In a proton flux experiment(solution pH 4.0),the cell membrane of 91532 exhibited a higher ability of blocking proton off and the cells had a high livability as well than the acid-sensitive strain.Its acid tolerance showed stable inheritance.