Envolvimento da proteína EnvZ nos processos de osmotolerância e fixação biológica de nitrogênio em Gluconacetobacter diazotrophicus

Abstract

Gluconacetobacter diazotrophicus is an endophytic diazotrophic bacterium originally isolated from plants of sugarcane and used as biofertilizers in culture. In order to prospect new genes involved directly or indirectly in Biological Nitrogen Fixation (BNF) in G. diazotrophicus (PAL5T) in previous studies was performed to select mutants affected in this process. The strain selected Mut29 was mutated in envZ gene homologous to that encoding an osmosensore protein. In other bacteria these proteins are involved in signal transduction to physiological responses such as: osmoregulation, motility, and production of extracellular polysaccharide involved in the pathogenesis of plants. This study aimed to evaluate the function of the osmosensore protein encoded by homologous to envZ of G. diazotrophicus. For this, the strains used PAL5T and Mut29 were grown in the cultivation LGI-P containing osmolytes increasing concentrations of sucrose, polyethylene glycol (PEG400) or sodium chloride (NaCl). This medium was evaluated tactical air film formation, acetylene reduction activity, motility, biofilm formation and analysis of expression of some genes by RT-qPCR. As a result it was observed that the strain PAL5T was capable of forming film and reduce acetylene at all concentrations of osmolytes used, except for some concentrations of sodium chloride. The Mut29 was not capable of forming film, characteristic of microorganism diazotrophic or to fix nitrogen in large concentrations of any of the treatments and medium. Moreover, the growth of this mutant at higher concentrations of different osmolytes was unaffected relative to PAL5T, indicating that other mechanisms related to osmotolerance in G. diazotrophicus. Tests for motility and biofilm formation in PAL5T indicate that envZ is related to production or handling of flagella. In conclusion, envZ has important functions in the metabolism of G. diazotrophicus, which need to be elucidated, suggesting that further studies should be conducted.