Project description:we studied the functional composition of a packed-bed nitrifying bioreactor inoculated with a co-culture of Nitrosomonas europaea (ATCC 25978) and Nitrobacter winogradskyi (ATCC 25391) after 840 days of operation.
Project description:Heavy metals have been postulated as significant nitrification inhibitor in wastewater treatment plant. The effect of heavy metals such as Cd2+, Cu2+ and Hg2+ to nitrifying bacterium, Nitrosomonas europaea, was studied in pseudo-steady state batch reactor. Under incubation of Nitrosomonas europaea with 1 ?M CdCl2 for 1 hour, transcripts for 66 of 2460 genes were found at high level, yet transcripts of 50 genes were found at low level. Mercury resistance genes (merACDPT) showed 277-fold up regulation. Keywords: cadmium, stress response, global transcription, mercury resistance genes, merA,
Project description:Nitrite-oxidizing bacteria are vital players in the global nitrogen cycle that convert nitrite to nitrate during the 2nd step of nitrification. Within this functional guild, the genus Nitrospira is among the most widespread and phylogenetically and physiologically diverse nitrite oxidizers and its members drive nitrite oxidation in many natural and biotechnological ecosystems. Despite their ecological and biotechnological importance, our understanding of Nitrospira’s energy metabolism is still limited. The main bottleneck for a detailed biochemical characterization of Nitrospira is biomass production, since they are slow-growing organisms and fastidious to culture. In this study, we cultured Nitrospira moscoviensis in a continuous stirred tank reactor system (CSTR) allowing constant biomass harvesting. Additionally, this cultivation setup enabled accurate control of physicochemical parameters and thus avoided fluctuating levels of nitrite and accumulation of nitrate. We performed transcriptome analysis and confirmed constant gene expression profiles in the chemostat culture over a period of two weeks. The transcriptomic data supports the predicted core metabolism of N. moscoviensis, including the reductive TCA cycle as a CO2 fixation pathway, the novel bd-like oxidase as terminal oxidase and the octaheme nitrite reductase involved in nitrogen assimilation. Additionally, the expression of multiple copies of respiratory complexes suggests functional differentiation of these copies within the respiratory chain. Transcriptome analysis also suggests a soluble and a membrane-bound gamma subunit as part of the nitrite oxidoreductase (NXR), the enzyme catalyzing nitrite oxidation. Overall, the transcriptome data provided novel insights into the metabolism of Nitrospira supporting the genome-based prediction of key pathways. Moreover, the application of a CSTR to cultivate Nitrospira is an important foundation for future proteomic and biochemical characterizations, which are crucial for a better understanding of canonical and complete nitrifying microorganisms.
Project description:Heavy metals have been postulated as significant nitrification inhibitor in wastewater treatment plant. The effect of heavy metals such as Cd2+, Cu2+ and Hg2+ to nitrifying bacterium, Nitrosomonas europaea, was studied in pseudo-steady state batch reactor. Under incubation of Nitrosomonas europaea with 1 ?M CdCl2 for 1 hour, transcripts for 66 of 2460 genes were found at high level, yet transcripts of 50 genes were found at low level. Mercury resistance genes (merACDPT) showed 277-fold up regulation. Keywords: cadmium, stress response, global transcription, mercury resistance genes, merA, The 1 uM CdCl2 caused more than 50 % inhibition in physiological response for 1 hour incubation. Transcriptional levels of the cells inhibited by cadmium were compared with the cells under control condition.