Production of quorum-sensing signaling molecules by bacteria isolated from rhizosphere of chickpea

VILCHEZ, LUCIANA ; NIEVAS ,FIORELA ; BOGINO, PABLO; INFANTE CIPRI, IVANA; AMIGO, JOSEFINA; GIORDANO, WALTER

San Miguel de Tucumán

Congreso; XII Congreso Argentino de Microbiología General (SAMIGE); 2017

Chickpea (Cicer arietinum L.), a important grain legume, forms a Nitrogen-fixing symbiosis with soil bacteria (rhizobia) that can be harnessed in agriculture to enable chickpea to be grown without nitrogen fertilizer. When cultivated in soil lacking compatible rhizobia, chickpea can be inoculated with a symbiotically effective strain of Mesorhizobium. In Argentina, Mesorhizobium ciceri has been the commercial inoculant for this crop. Many bacteria, including rhizobia, use a molecular communication system, referred to as quorum sensing (QS), to synchronize the expression of certain genes and adopt a group behavior. Specifically QS communication via AHLs in rhizobia affects many metabolic and physiological process, including motility, exopolysaccharide production, biofilm formation, plasmid transfer, root nodulation efficiency, and nitrogen fixing efficiency. Previous studies in our laboratory demonstrated the existence of cell communication mechanisms among bradyrhizobial strains symbiotic of peanut. In this work, we investigated efficiency of inoculation of chickpea with M. ciceri in an assay carried out in the experimental field of the Facultad de Agronomia y Zootecnia ? Universidad Nacional de Tucumán, located in the town of El Manantial. We used Norteño variety seeds treated with fungicide products and inoculated with commercial liquid inoculation at the doses suggested by the manufacturer. In addition the QS signals produced by bacterial strains isolated from root nodule and rhizosphere was tested. Our study indicated that there was a positive response to inoculation, which suggests that it is a recommended practice for this important legume crop. On the other way, detection of AHLs in bacteria strains was performed using the biosensor strains Agrobacterium tumefaciens NTL4 (pZLR4) and Chromobacterium violaceum CV026 for AHLs with long and short acyl chains, respectively. Total of 100 strains isolated from the rhizosphere, 31% showed production for short chain (8 strains) and long chain (27 strains) AHL. Qs activity was detected in one recommended strains for inoculation this crop. Our results demonstrate the existence of cell communication mechanisms among bacterial strains interacting with chickpea roots. Further characterizations of the phenotypes regulated by quorum-sensing signaling molecules are underway.