Colonization of Catharanthus roseus by Methylobacterium extorquens wild type and mutants defective in biofilm formation and acyl-homoserine-lactone production

SANTOS GAI, C., NIETO PEÑALVER, C., BARROS ROSSETTO, P., TEIXEIRA LACAVA, P., VORHOLT, J., ARAÚJO, W.L., AZEVEDO, J.L

Sorrento, Italia

Congreso; XIII International Congress on Molecular Plant-Microbe Interactions; 2007

Endophytes are microorganisms that inhabit the interior of plant tissues. They cause no harm and may help the host plants in conferring resistance to insects, diseases, environmental adverse conditions and might influence plant growth. Methylobacterium extorquens is a common endophytic bacterium isolated form different plants, such as citrus, soy been, sugar cane, eucalyptus, mango, among others. In the present study, we analyzed whether biofilm production and synthesis of acyl-homoserine lactones (AHL) affects plant colonization by M. extorquens. Mutants defective in biofilm formation and production of AHL, respectively, were generated via random transposon mutagenesis. One mutant was effected in both characters suggesting that biofilm formation is at least partially regulated by quorum sensing in the methylotrophic Alphaproteobacterium. Infection experiments with these mutants as well as the wild type strain and water as a negative control were performed and bacterial counts determined on selective medium after isolation from stems of 15 plants after 45, 60, and 90 days. Biofilm-defective mutants showed a faster initial colonization of the plant. In general, the failure to produce biofilms and AHL resulted in higher final concentration of bacteria inside the plant relative to the wild type. For the different mutants a different colonization pattern was observed which suggests that biofilm and AHL production is of influence for plant colonization by the endophytic bacterium M. extorquens.