Differentiation of Rhizobium japonicum strain derivatives by antibiotic sensitivity patterns, lectin binding, and utilization of biochemicals

Abstract

Several strains of Rhizobium japonicum have been reported to consist of mixtures of stable derivatives having distinct colony morphologies and physiological characteristics. We isolated derivatives from strains of R. japonicum and systematically compared them with previously isolated derivatives with respect to the utilization of biochemicals, antibiotic sensitivity, and soybean lectin binding. With the exception of a pair of derivatives from 3I1b 110, one of which utilized pyruvate and one of which did not, sibling derivatives had essentially identical biochemical utilization patterns. The sibling derivatives of parental strains 3I1b 110 and 3I1b 140 exhibited marked variation in their sensitivities to several antibiotics, including gentamicin, sulfamethoxazole, and tetracycline. Compared with the derivatives with small colony morphology, derivatives with large colony morphology were in general more sensitive to these antibiotics. With one exception, the binding of soybean lectin to the derivatives was quantitatively the same as that to the parental strain. The anomaly was 110-Y which, in contrast to its parental strain and sibling derivatives, failed to bind detectable amounts of the lectin. 110-Y, as well as all the other derivatives and parental strains, nodulated Disoy soybean.