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

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 N 2 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 NO 3 - , NO 2 - and NH 4 + 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 o 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 N 2 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.