Atividade das lectinas de Canavalia brasiliensis e Canavalia ensiformis sobre o crescimento “in vitro” de Rhizobium tropici

Abstract

Rizobia are gram-negative bacteria that lives as symbiotic cells in roots of leguminous inducing the formation of nodules. Inside of these nodules, these bacteria in their endosymbiotic life style, fixate the atmospheric nitrogen and make it available for the cells from the host plant. Different environment conditions are limiting factors for the biological nitrogen fixation and for the plant development, like drought-stressed, salinity, pH and temperature. Rhizobium tropici CIAT899 is a rizobia‟s strain that has effective symbioses with Phaseolus vulgaris, this strain shows tolerance to many different environment stress, such as high temperatures, acid environment and high salinity. Lectins are (glico) proteins from non-immune origin that binds specific and reversible to carbohydrates or to glicoconjugates. Due to their capacity of recognizing specific carbohydrates, lectins shows to be an important tool that helps the interaction between rizobia and the host plant. In this work we tried to demonstrate the activity of the lectin isolated from Canavalia brasiliensis (ConBr) and Canavalia ensiformis seeds on the in vitro growth of Rhizobium tropici. The data demonstrate that the lectin ConBr was capable of stimulating, in a significant way, the in vitro growth of Rhizobium tropici. The effect that was found was reverted in the presence of the inhibitory sugar (mannose), suggesting an effective lectin activity. However the lectin ConA didn‟t show any activity on the growth of the microorganisms. The ConBr-FITC conjugates, as been expected, showed interaction between the bacteria surface, these results were similar with those from ConA, although this lectin doesn‟t show any activity in the microbial growth of Rhizobium tropici. The difference between the biological activities of these similar lectins, probably is due to their structure differences in the carbohydrate binding domain.