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

LUCIANA VILCHEZ; FIORELA L. NIEVAS; PABLO C. BOGINO; IVANNA LUZ INFANTE CIPRI; JOSEFINA AMIGO; WALTER GIORDANO

Congreso; XII Congreso Argentino de Microbiología General; 2017

Chickpea (Cicer arietinum L.), a important grain legume, forms a Nitrogen-fixing symbiosis with soilbacteria (rhizobia) that can be harnessed in agriculture to enable chickpea to be grown without nitrogenfertilizer. When cultivated in soil lacking compatible rhizobia, chickpea can be inoculated witha symbiotically effective strain of Mesorhizobium. In Argentina, Mesorhizobium ciceri has been thecommercial inoculant for this crop. Many bacteria, including rhizobia, use a molecular communicationsystem, referred to as quorum sensing (QS), to synchronize the expression of certain genes andadopt a group behavior. Specifically QS communication via AHLs in rhizobia affects many metabolicand physiological process, including motility, exopolysaccharide production, biofilm formation, plasmidtransfer, root nodulation efficiency, and nitrogen fixing efficiency. Previous studies in our laboratorydemonstrated the existence of cell communication mechanisms among bradyrhizobial strains symbioticof peanut. In this work, 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 Nacionalde Tucumán, located in the town of El Manantial. We used Norteño variety seeds treated with fungicideproducts 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 rhizospherewas tested. Our study indicated that there was a positive response to inoculation, which suggests thatit is a recommended practice for this important legume crop. On the other way, detection of AHLs inbacteria 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 of100 strains isolated from the rhizosphere, 31% showed production for short chain (8 strains) and longchain (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 interactingwith chickpea roots. Further characterizations of the phenotypes regulated by quorum-sensingsignaling molecules are underway.