Nitrogen utilization and transformation of Stenotrophomonas maltophilia W-6 with nitrogen-fixing ability

Abstract

Strain W-6 was isolated from the purple soil and successfully identifed as Stenotrophomonas maltophilia and used for the investigation on nitrogen utilization. Strain W-6 was monitored with the ability of biological nitrogen fixation when N2 was used for the sole nitrogen source, and yet nitrogenase activity would be inhibited in the presence of extra nitrogen. Moreover, Strain W-6 could utilize NO3-, NO2- and NH4+ for cell growth through assimilation, but unable to convert them to atmospheric nitrogen. Meantime, accumulation of nitrite was observed during the nitrate removal process, and the optimal conditions for nitrate removal were temperature of 20{degrees}C, shaking speed of 150 rpm, sodium succinate as the carbon source and C/N of 12. The experimental results indicate that Stenotrophomonas maltophiliautilize W-6 could utilize not only N2 but also other nitrogen sources directly as its N substance. Therefore, heterotrophic Azotobacter may possess a great significance to nitrogen cycle except in biological nitrogen fixation.\n\nImportanceAzotobacter spp. are found in soils worldwide, with features not simply for the nitrogen fixation, but for the energy metabolism relevant to agriculture. However, the role of Azotobacter potential in the function of nitrogen cycle except in biological nitrogen fixation is largely unknown. As such, whether bacteria utilize either inorganic nitrogen or organic nitrogen has remained obscure. The present studies indicate that Stenotrophomonas maltophilia W-6 could highly efficient utilize nitrate, nitrite and ammonium etc. N substance and detect NH4+ as final product. The transport velocities of nitrate-N to nitrite-N was quickly without gaseous nitrogen was produced. We probed the relationship between biological nitrogen fixation and N cycle via N conversion processes by S. maltophilia W-6 with nitrogen-fixing ability