Direct monitoring of Rhizobium sp. (Cicer) in nodules and soil using lac Z fusions

• Published in: Biology and fertility of soils 1996-03, Vol.21 (4), p.309-313
• Main Authors: Kamboj, D.V, Sharma, P.K, Kundu, B.S
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; Biotechnology; Cicer; competitive ability; detection; Economic plant physiology; enumeration; Environment and pollution; Fundamental and applied biological sciences. Psychology; genetic engineering; genetic markers; genetically engineered microorganisms; Genetically engineered organisms behavior (microorganisms, plants, animals); identification; indigenous versus introduced strains; Industrial applications and implications. Economical aspects; inoculum; lacz genes; Microbial ecology; monitoring; mutants; nodulation; Rhizobium; Soil; soil bacteria; strains; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...)
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/BF00334908

We constructed lacZ fusions in Rhizobium sp. (Cicer) by random Tn5-lacZ mutagenesis. The lacZ+ I fusants formed blue colonies on a Rhizobial minimal medium containing 5-bromo-4-chloro-3-indolyl-beta-D -galactopyranoside (X-gal). Rhizobium sp. (Cicer) fusant HSL-2 was identified in nodules and soil in a mixed population on the basis of the lacZ+ phenotype. Nodule occupancy of inoculated Rhizobium sp. (Cicer) HSL-2 (lacZ+) was assessed by directly streaking the nodule sap on X-gal plates. This method revealed differences between rhizobia carrying identical antibiotic markers. The rhizobial population in soil was estimated by direct plate counts using a medium containing X-gal. Introduction of lacZ into the Rhizobium sp. thus provided a simple and direct method for identifying strains from nodules and soil.