RESUMO
In the present study, we analyzed the frequency of hemolytic and antifungal activities in bacterial isolates from the rhizosphere of Medicago truncatula plants. Of the 2000 bacterial colonies, 96 showed ß-hemolytic activities (frequency, 4.8 x 10(-2)). Hemolytic isolates were analyzed for their genetic diversity by using random amplification of polymorphic DNA, yielding 88 haplotypes. The similarity coefficient of Nei and Li showed a polymorphic diversity ranging from 0.3 to 1. Additionally, 8 of the hemolytic isolates showed antifungal activity toward plant pathogens, Diaporthe phaseolorum, Colletotrichum acutatum, Rhizoctonia solani, and Fusarium oxysporum. The 16S ribosomal sequencing analysis showed that antagonistic bacterial isolates corresponded to Bacillus subtilis (UM15, UM33, UM42, UM49, UM52, and UM91), Bacillus pumilus (UM24), and Bacillus licheniformis (UM88). The present results revealed a higher genetic diversity among hemolytic isolates compared to that of isolates with antifungal action.
Assuntos
Bacillus subtilis/genética , Bacillus/genética , Medicago truncatula/microbiologia , Filogenia , RNA Ribossômico 16S/genética , Microbiologia do Solo , Antibiose , Antifúngicos/metabolismo , Antifúngicos/farmacologia , Bacillus/classificação , Bacillus/metabolismo , Bacillus subtilis/classificação , Bacillus subtilis/metabolismo , Técnicas de Tipagem Bacteriana , Fusarium/efeitos dos fármacos , Fusarium/crescimento & desenvolvimento , Variação Genética , Haplótipos , Hemólise , Técnica de Amplificação ao Acaso de DNA Polimórfico , Rhizoctonia/efeitos dos fármacos , Rhizoctonia/crescimento & desenvolvimento , RizosferaRESUMO
Gene families are an important and intrinsic trait of rhizobial species. These gene copies can participate in non-reciprocal recombination events, also called gene conversions. Gene conversion has diverse roles, but it is usually implicated in the evolution of multigene families. Here, we searched for gene conversions in multigene families of six representative rhizobial genomes. We identified 11 gene families with different numbers of copies, genome location and function in CFN42 and CIAT652 strains of Rhizobium etli, Rhizobium sp NGR234, Mesorhizobium loti MAFF303099, Sinorhizobium meliloti 1021, and Bradyrhizobium japonicum USDA110. Gene conversions were detected by phylogenetic inference in the nifD and nifK gene families in R. etli. Sequence analysis confirmed multiple gene conversions in these two gene families. We suggest that gene conversion events have an important role in homogenizing multigene families in rhizobia.