Heat Shock Tolerant Mutants of Rhizobium meliloti Forming Ineffective Nodules

Six heat shock tolerant mutants of Rhizobium meliloti Rmd201 were isolated through transposon Tn5 mutagenesis. The symbiotic assays of these mutants with alfalfa plants, showed four of these mutants to be affected in nitrogenase effectivity also. These four mutants could be classified into two separate complementation groups hssA and hssC through R-prime mediated merodiploid constructions. The hssC mutant Rmd1040 also showed poor interaction with phages indicating surface alterations. The results indicated possible involvement of these loci in symbiosis as well as heat shock response.