IIBIO   27936
Unidad Ejecutora - UE
congresos y reuniones científicas
Regulation of swimming motility and biofilm formation in Mesorhizobium loti: study of the role of second messengers
Congreso; LV Reunion Anual SAIB; 2019
Institución organizadora:
Sociedad Argentina de Investigación en Bioquímica y Biología Molecular
ABSTRACTREGULATION OF SWIMMING MOTILITY AND BIOFILM FORMATION IN MESORHIZOBIUM LOTI: STUDY OF THE ROLE OF SECOND MESSENGERSBasile LA, Escobar M, Lepek VCInstituto de Investigaciones Biotecnológicas (IIBIO-CONICET-UNSAM). Buenos Aires, ArgentinaE-mail: lbasile@iibintech.com.arEarly steps of nodule development in rhizobia-legume symbiosis involve the induction of the bacterial Type III secretion system (T3SS) by specific flavonoids secreted by the leguminous plants. Flagella promote swimming and swarming motility in free-living bacteria being required for the bacterial movement to the roots proximity and attachment to the root hairs. We had previously described a negative regulation of swimming motility in soft-agar under T3SS induction conditions in Mesorhizobium loti MAFF303099. The transcriptional factor TtsI (which positively regulates T3SS genes expression) was involved in the inhibition of motility. Expression of visN gene (a positive regulator for flagellar genes) and flagella production were also affected under T3SS induction conditions. In this work we started to evaluate the role of the second messengers c-diGMP and cAMP in motility regulation, biofilm formation and interaction with the leguminous Lotus sp. A M. loti strain overexpressing a phosphodiesterase of c-diGMP (PDE, mll2537) did not show inhibition of swimming motility under T3SS induction conditions, suggesting a role of c-diGMP levels in the negative regulation of motility. Biofilm formation was increased in the wild type strain under T3SS induction conditions, but not in the strain overexpressing mll2537 gene. This indicates that c-diGMP levels would be also implicated in the regulation of biofilm formation. The promoter region of the mll9676 gene (a fosfoesterase of c-AMP) presents a tts-box like sequence. By fusion to the b-galactosidase gene, the activity of this promoter region was evaluated. Preliminary results showed activity at late-exponential growth phase, both in the wild type as in the ttsI mutant strain. Similar levels of promoter activity were detected for the wild type strain grown with or without T3SS induction conditions. These results suggest that mll9676 gene is not under a direct regulation of the TtsI transcriptional factor. M. loti mutant strains for genes of c-diGMP and c-AMP metabolism are being constructed. In addition to biofilm and motility assays, their role in nodulation will be determined by inoculation of these strains in Lotus tenuis plants.