PRODUCTION OF QUORUM-SENSING SIGNALING MOLECULES BY BACTERIA ISOLATED FROM RHIZOSPHERE OF CHICKPEA

VILCHEZ L; NIEVAS F.L; BOGINO P.C; INFANTE CIPRI AL; AMIGO JOSEFINA

San Miguel de Tucuman

Congreso; XII congreso argentino de microbiologia general; 2017

Chickpea (Cicer arietinum L.), a important grain legume, forms a Nitrogen-fixingsymbiosis with soil bacteria (rhizobia) that can be harnessed in agriculture to enablechickpea to be grown without nitrogen fertilizer. When cultivated in soil lackingcompatible rhizobia, chickpea can be inoculated with a symbiotically effective strain ofMesorhizobium. In Argentina, Mesorhizobium ciceri has been the commercial inoculantfor this crop. Many bacteria, including rhizobia, use a molecular communication system,referred to as quorum sensing (QS), to synchronize the expression of certain genes andadopt a group behavior. Specifically QS communication via AHLs in rhizobia affectsmany metabolic and physiological process, including motility, exopolysaccharideproduction, biofilm formation, plasmid transfer, root nodulation efficiency, and nitrogenfixing efficiency. Previous studies in our laboratory demonstrated the existence of cellcommunication mechanisms among bradyrhizobial strains symbiotic of peanut. In thiswork, we investigated efficiency of inoculation of chickpea with M. ciceri in an assaycarried out in the experimental field of the Facultad de Agronomia y Zootecnia ?Universidad Nacional de Tucumán, located in the town of El Manantial. We usedNorteño variety seeds treated with fungicide products and inoculated with commercialliquid inoculation at the doses suggested by the manufacturer. In addition the QSsignals produced by bacterial strains isolated from root nodule and rhizosphere wastested. Our study indicated that there was a positive response to inoculation, whichsuggests that it is a recommended practice for this important legume crop. On the otherway, detection of AHLs in bacteria strains was performed using the biosensor strainsAgrobacterium tumefaciens NTL4 (pZLR4) and Chromobacterium violaceum CV026 forAHLs with long and short acyl chains, respectively. Total of 100 strains isolated from therhizosphere, 31% showed production for short chain (8 strains) and long chain (27strains) AHL. Qs activity was detected in one recommended strains for inoculation thiscrop. Our results demonstrate the existence of cell communication mechanisms amongbacterial strains interacting with chickpea roots. Further characterizations of thephenotypes regulated by quorum-sensing signaling molecules are underway.