Nitrogen source assimilation of a <I>Vibrio alginolyticus</I> strain under different C/N ratios

Abstract

Nitrogen assimilation characteristics of a Vibrio alginolyticus strain(Z5) were investigated under both single(organic nitrogen, NH4-N, or NO2-N) and mixed nitrogen sources(organic nitrogen and NH4-N, organic nitrogen and NH4-N, or NH4-N, and NO2-N) at C/N ratios of 5, 10, 15, and 20 respectively. Activity of protease,glutamine synthetase, and nitrite reductase, which are all involved in nitrogen metabolism, was also determined.The results showed that both organic and inorganic nitrogen assimilation rates of V. alginolyticus were affected by C/N ratio. NH4-N and NO2-N assimilation rates under a C/N ratio of 20 were 3.39 and 2.25 times higher, respectively, than those under a C/N ratio of 5. There were no significant differences in the assimilation of NH4-N and NO2-N between C/N ratios of 15 and 20(P0.05). The NH4-N and NO2-N assimilation processes may be NH4-N→bacterial protein and NO2-N→NH4-N→bacterial protein, respectively. Inorganic nitrogen(NH4-N and NO2-N) assimilation rates increased with higher C/N; the protein nitrogen content of the bacteria enriched from NH4-N and NO2-N increased from 25.0% and 19.4% under a C/N of 5 to 41.3% and 43.0% under a C/N of 20,respectively. In addition, glutamine synthetase activity was significantly regulated by NH4-N while protease and NiR activity were not regulated significantly by the nitrogen species.