RESISTANCE OF KARST CAVERNS NITROGEN-FIXING BACTERIA TO EXTREME FACTORS

Abstract

To determine the studied bacteria resistance quantitative parameters of extreme factors such as toxic metals (Cu2+), organic xenobiotics (p-nitrochlorobenzene) and UV-irradiation were the aim of the research. Six strains of nitrogen-fixing bacteria isolated from clays of two caverns Mushkarova Yama (Podolia, Ukraine) and Kuybyshevskaya (Western Caucasus, Abkhazia) and Azotobacter vinelandii УКМ В-6017 as a reference strain have been tested. For this purpose the maximum permissible concentration of Cu2+ and p-nitrochlorobenzene in the concentration gradient and lethal doses of UV by the survival caverns have been determined. Maximum permissible concentrations for strains were as 10 ppm Cu2+, 70–120 ppm of p-nitrochlorobenzene. The maximum doses of UV-irradiation varied in the range of 55–85 J/m2 (LD99.99). It is shown that three classes of extreme factors resistance parameters of karst caverns strains are similar to the strain of terrestrial soil ecosystems. The most active studied strains reduce the concentration of p-nitrochlorobenzene in the medium in 13 times. The ability of nitrogen-fixing bacteria to degrade p-nitrochlorobenzene could be used in creation new environmental biotechnology for industrial wastewater treatment from nitrochloroaromatic xenobiotics. Isolated strains could be used as destructors for soils bioremediation in agrobiotechnologies and to optimize plants nitrogen nutrition in terrestrial ecosystems.

Keywords

• karst caverns
• nitrogen-fixing bacteria
• environmental biotechnology