دانلود رایگان مقاله بیان ژن و کشف نشانگر باکتری آناموکس در راکتورهای مختلف

BSTRACT

Themultiplicity and heterogeneity of anaerobic ammonia oxidation (anammox) bacteriamake their absolute quantification difficult. To reveal the quantitative relationships among the 16S rRNA gene and typical functional genes (nir, hzo and hzs genes) in the anammox process and their quantitative association with nitrogen removal (ammonium and nitrite), the genes were extracted from four reactors and quantified by real-time quantitative PCR (q-PCR). The Pearson correlation coefficients among the associated genes exceeded 0.96 (P < 0.01), and the q-PCR results indicated that the relative copy numbers (compared with the level of the hzo gene, which was set as 1) of the hzs gene, nir gene and 16S rRNA gene per cell were 8.00, 25.22 and 157.67, respectively. Nitrogen removal efficiency was directly proportional to the logarithm of the gene concentration, with most of the R2 values being greater than 0.9. The functional genes, especially hzo and hzs, are more suitable to assess anammox activity with the R2 values of fitted equations being greater than 0.96. The mRNA quantity did not correlate with the system nitrogen removal performance directly because of different enzyme activities. This study provided valuable reference data to further reveal the molecular mechanism of anammox metabolism.

4. Conclusions

Nucleic acid (DNA & mRNA) concentrations were quantified to explore the relationships among the 16S rRNA gene, functional genes and their quantity compared with nitrogen removal. The results suggested that an anammox bacterium cell contains more than one copy of the functional genes and the 16S rRNA gene. The nitrogen removal efficiency was in direct proportion to the logarithm of the gene concentration. Functional genes, especially hzo and hzs, are more suitable than the 16S rRNA gene to assess anammox activity, with R2 values of the fitted equation over 0.96. The mRNA quantities were difficultto correlate directly with the anam-mox performance because of the different enzyme activities under different operation conditions.