德国联邦营养研究中心( Federal Research Centre for Nutri tion)的加工工程技术研究所的研究组发现脱氮细菌(还原硝酸成为氨气的微生物)对减少蔬菜汁液中过量的硝酸盐(nitrate)有效。硝酸本身几乎没有一次毒性,但是一旦摄食,由于口腔...德国联邦营养研究中心( Federal Research Centre for Nutri tion)的加工工程技术研究所的研究组发现脱氮细菌(还原硝酸成为氨气的微生物)对减少蔬菜汁液中过量的硝酸盐(nitrate)有效。硝酸本身几乎没有一次毒性,但是一旦摄食,由于口腔内细菌和肠内细菌的作用而还原成活性型亚硝酸(nitrite)。因此,德国和欧共体(EC)规定上限浓度。实际对减少胡萝卜汁液的硝酸浓度有效。展开更多
This study attempted to determine the characteristics of the communities, the ecological factors, and the denitrifying enzyme activity for denitrifying bacteria found in the paddy soils of the Taihu Lake Basin, China....This study attempted to determine the characteristics of the communities, the ecological factors, and the denitrifying enzyme activity for denitrifying bacteria found in the paddy soils of the Taihu Lake Basin, China. Samples of the six main soil types of the basin were taken from paddy fields with different fertilities. The total numbers of bacteria and denitrifying bacteria in the high fertility soils were much more than those in low fertility soils, and the number of denitrifying bacteria accounted for 49% to 80% of the total number of bacteria. The O2 content was an important ecological factor that affected denitrification. Of test the strains isolated from the paddy soils in the Taihu Lake Basin, some (e.g., Pseudomonas spp.) grew well under low oxygen partial pressure, while others (e.g., Bacillus spp.) had no strict predilection with O2 content. Another critical ecological factor was the nitrogen concentration. Three selected denitrifying bacteria grew better in aculture medium with 135 instead of 276mg L^-1 nitrogen. At the same time 67% of the test strains were able to reduce NO3^- to NO2^- and 56% had N2O reductase.展开更多
This is the first time to describe the diversity of denitrifying bacteria in Sanjiangyuan natural reserve in Tibet Plateau by investigating the molecular diversity and phylogenetic analysis of nirK and nosZ genes usin...This is the first time to describe the diversity of denitrifying bacteria in Sanjiangyuan natural reserve in Tibet Plateau by investigating the molecular diversity and phylogenetic analysis of nirK and nosZ genes using PCR-RFLP and sequencing. Four soil samples were collected from alpine meadow communities from over an altitude of 4600 m which had different physicochemical properties by principal component analysis (PCA). For the genes fragment of nirK and nosZ, the diverse PCR products were characterized by cloning, restriction fragment length polymorphism (RFLP) analysis and sequenced. A total of 253 nirK clones and 283 nosZ clones were received in four samples, and 78 operational taxonomic units (OTUs) of nirK and 120 OTUs of nosZ by the restriction enzymes MspI and RsaI digested. The analysis of environmental factors showed that altitude and C/N ratio in soil may be the key factors to the denitrifying bacteria community. 36 nirK clones and 17 nosZ clones were sequenced, and their levels of nucleotide identity were from 69% to 98% and 57% to 97%, respectively. The phylogenetic tree was constructed using the Clustal W and Mega softwares, and all the sequenced clones could be subdivided into 4 groups. Some of clone sequences were related to the nirK and nosZ genes belonging to three phylogenetic subdivisions (α-, β- and γ subclasses of the Proteobacteria), while most of the clones were closely related to the genes of the uncultured bacteria. The sequence distributions were not clear relating to the sample sites in the tree.展开更多
Literatures revealed that the electron acceptor-nitrite could be inhibitory or toxic in the denitrifying phosphorus removal process. Batch test experiments were used to investigate the inhibitory effect during the ano...Literatures revealed that the electron acceptor-nitrite could be inhibitory or toxic in the denitrifying phosphorus removal process. Batch test experiments were used to investigate the inhibitory effect during the anoxic condition. The inoculated activated sludge was taken from a continuous double-sludge denitrifying phosphorus and nitrogen removal system. Nitrite was added at the anoxic stage. One time injection and sequencing batch injection were carried on in the denitrifying dephosphorus procedure. The results indicated that the nitrite concentration higher than 30 mg/L would inhibit the anoxic phosphate uptake severely,and the threshold inhibitory concentration was dependent on the characteristics of the activated sludge and the operating conditions; instead,lower than the inhibitory concentration would not be detrimental to anoxic phosphorus uptake,and it could act as good electron acceptor for the anoxic phosphate accumulated. Positive effects performed during the denitrifying biological dephosphorus all the time. The utility of nitrite as good electron acceptor would provide a new feasible way in the denitrifying phosphorus process.展开更多
文摘德国联邦营养研究中心( Federal Research Centre for Nutri tion)的加工工程技术研究所的研究组发现脱氮细菌(还原硝酸成为氨气的微生物)对减少蔬菜汁液中过量的硝酸盐(nitrate)有效。硝酸本身几乎没有一次毒性,但是一旦摄食,由于口腔内细菌和肠内细菌的作用而还原成活性型亚硝酸(nitrite)。因此,德国和欧共体(EC)规定上限浓度。实际对减少胡萝卜汁液的硝酸浓度有效。
基金Project supported by the National Natural Science Foundation of China (No. 39770024).
文摘This study attempted to determine the characteristics of the communities, the ecological factors, and the denitrifying enzyme activity for denitrifying bacteria found in the paddy soils of the Taihu Lake Basin, China. Samples of the six main soil types of the basin were taken from paddy fields with different fertilities. The total numbers of bacteria and denitrifying bacteria in the high fertility soils were much more than those in low fertility soils, and the number of denitrifying bacteria accounted for 49% to 80% of the total number of bacteria. The O2 content was an important ecological factor that affected denitrification. Of test the strains isolated from the paddy soils in the Taihu Lake Basin, some (e.g., Pseudomonas spp.) grew well under low oxygen partial pressure, while others (e.g., Bacillus spp.) had no strict predilection with O2 content. Another critical ecological factor was the nitrogen concentration. Three selected denitrifying bacteria grew better in aculture medium with 135 instead of 276mg L^-1 nitrogen. At the same time 67% of the test strains were able to reduce NO3^- to NO2^- and 56% had N2O reductase.
文摘This is the first time to describe the diversity of denitrifying bacteria in Sanjiangyuan natural reserve in Tibet Plateau by investigating the molecular diversity and phylogenetic analysis of nirK and nosZ genes using PCR-RFLP and sequencing. Four soil samples were collected from alpine meadow communities from over an altitude of 4600 m which had different physicochemical properties by principal component analysis (PCA). For the genes fragment of nirK and nosZ, the diverse PCR products were characterized by cloning, restriction fragment length polymorphism (RFLP) analysis and sequenced. A total of 253 nirK clones and 283 nosZ clones were received in four samples, and 78 operational taxonomic units (OTUs) of nirK and 120 OTUs of nosZ by the restriction enzymes MspI and RsaI digested. The analysis of environmental factors showed that altitude and C/N ratio in soil may be the key factors to the denitrifying bacteria community. 36 nirK clones and 17 nosZ clones were sequenced, and their levels of nucleotide identity were from 69% to 98% and 57% to 97%, respectively. The phylogenetic tree was constructed using the Clustal W and Mega softwares, and all the sequenced clones could be subdivided into 4 groups. Some of clone sequences were related to the nirK and nosZ genes belonging to three phylogenetic subdivisions (α-, β- and γ subclasses of the Proteobacteria), while most of the clones were closely related to the genes of the uncultured bacteria. The sequence distributions were not clear relating to the sample sites in the tree.
基金Supported by the Science and Technology Project of Heilongjiang Province (Grant No. GA01C201-03)
文摘Literatures revealed that the electron acceptor-nitrite could be inhibitory or toxic in the denitrifying phosphorus removal process. Batch test experiments were used to investigate the inhibitory effect during the anoxic condition. The inoculated activated sludge was taken from a continuous double-sludge denitrifying phosphorus and nitrogen removal system. Nitrite was added at the anoxic stage. One time injection and sequencing batch injection were carried on in the denitrifying dephosphorus procedure. The results indicated that the nitrite concentration higher than 30 mg/L would inhibit the anoxic phosphate uptake severely,and the threshold inhibitory concentration was dependent on the characteristics of the activated sludge and the operating conditions; instead,lower than the inhibitory concentration would not be detrimental to anoxic phosphorus uptake,and it could act as good electron acceptor for the anoxic phosphate accumulated. Positive effects performed during the denitrifying biological dephosphorus all the time. The utility of nitrite as good electron acceptor would provide a new feasible way in the denitrifying phosphorus process.
