Cultural conditions required for the induction of an adaptive acid-tolerance response (ATR) in Sinorhizobium meliloti and the question as to whether or not the ATR helps rhizobia improve their symbiosis with alfalfa at low pH.
Laboratory prescreening ofRhizobium trifolii for acid tolerance, based upon the ability of rhizobia to grow in acid media (pH 4.2) containing Al (15 μM), was successful for the selection of strains capable of survival in acid soil. Both sterile and non-sterile soils of varying acidity were inoculated with several strains ofR. trifolii. Acid tolerant strains generally had significantly higher populations at every sample period than an acid sensitive strain. Amelioration of soil acidity by liming improved persistence of all strains. Soil sterilization by autoclaving adversely affected survival of all strains at each soil acidity level.