Nodulating strains of Rhizobium loti arise through chromosomal symbiotic gene transfer in the environment.

AUTOR(ES)

Sullivan, J T

RESUMO

Rhizobia were isolated from nodules off a stand of Lotus corniculatus established with a single inoculant strain, ICMP3153, 7 years earlier in an area devoid of naturalized Rhizobium loti. The isolates showed diversity in growth rate, Spe I fingerprint of genomic DNA, and hybridization pattern to genomic DNA probes. The 19% of isolates that grew at the same rate as strain ICMP3153 were the only isolates that had the same fingerprint as strain ICMP3153. Sequencing of part of the 16S rRNA gene of several diverse isolates confirmed that they were not derived from the inoculant strain. Nevertheless, all non-ICMP3153 strains gave EcoRI and Spe I hybridization patterns identical to ICMP3153 when hybridized to nodulation gene cosmids. Hybridization of digests generated by the very rare cutting enzyme Swa I revealed that the symbiotic DNA region (at least 105 kb) was chromosomally integrated in the strains. The results suggest that the diverse strains arose by transfer of chromosomal symbiotic genes from ICMP3153 to nonsymbiotic rhizobia in the environment.

Documentos Relacionados

• Bacterial gene transfer by natural genetic transformation in the environment.
• Symbiotic effectiveness and ecological characterization of indigenous Rhizobium loti populations in Uruguay.
• Exopolysaccharide mutants of Rhizobium loti are fully effective on a determinate nodulating host but are ineffective on an indeterminate nodulating host.
• Diversity of Plasmid Profiles and Conservation of Symbiotic Nitrogen Fixation Genes in Newly Isolated Rhizobium Strains Nodulating Sulla (Hedysarum coronarium L.)
• Isolation and characterization of transposon Tn5-induced symbiotic mutants of Rhizobium loti.