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

Several strains of Rhizobium japonicum have been reported to consist of mixtures of stable derivativess 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 soyben lectin binding. With the exception of a pair of derivatives from 3Ilb110, 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 3Ilb110 and 3Ilb140 exhibited marked variation in their sensitivities to several antibiotics, including gentamicin, sul famethoxazole, and tetracycline. Compared with the derivative 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.