Effect of some abiotic factors on the biological activity of Gluconacetobacter diazotrophicus

Aims: The effect of some abiotic factors, dryness, heat and salinity on the growth and biological activity of Gluconacetobacter diazotrophicus , and the influence of a salt stress on some enzymes involved in carbon metabolism of these bacteria is studied under laboratory conditions. Methods and Results: Strain PAL-5 of G. diazotrophicus was incubated under different conditions of drying, heat and salinity. Cells showed tolerance to heat treatments and salt concentrations, and sensitivity to drying conditions. Higher NaCl dosage of 150 and 200 mmol l (-1) limited its growth and drastically affected the nitrogenase activity and the enzymes glucose dehydrogenase, alcohol dehydrogenase, fumarase, isocitrate dehydrogenase and malate dehydrogenase. Conclusions: Gluconacetobacter diazotrophicus , despite its endophytic nature, tolerated heat treatments and salinity stress, but its nitrogenase activity and carbon metabolism enzymes were affected by high NaCl dosage. Significance and Impact of the Study: The investigation of the biological activity of G. diazotrophicus in response to different abiotic factors led to more knowledge of this endophyte and may help to clarify pathways involved in its transmission into the host plant.