Study On The Ecological Security Of Nitrifying Bacteria Agents

In aquaculture system, microbial agents improve the health of aquaculture species and aquaculture environment by regulating micro-ecological balance in water, adjusting the biological environment and purifing water. After twenty years of development, microbial agents in aquaculture as became an emerging industry. But the current researches of microbial agents are mostly limited to effect, strain selection, application conditions, method and dose, however, interaction and compatibility between species, function mechanism, environmental effect, preserve method, recycling and elimination technologies are seriously lagging behind, especially, in the selection of strains. To study how to choose the safe, non-toxic side effects strains is more important. In this study, a series of low-moderate to high,such as luminescent bacteria, algaes, Daphnia, and fish were chosed as the biological subjects, as well as the pathogen detection, and drug resistance tests were also conducted . The results of the investigation are as follows:(1) In a short contact time, the nitrifying bacteria agents had a low inhibition rate on luminescent bacteria and there's no obvious correlation. When the contact time reached to 30 min, EC20 was 74.6% of the sample dilution ratio. The inhibition of nitrifying bacteria on luminescent bacteria was not obvious.(2) Study the impact of nitrifying bacteria on the growth of Chlorella vulgaris and Scenedesmus obliquus throughout the life cycle showed there's no inhibition on algaes, but had a facilitating role. When the promotion rate of 50%, for Chlorella vulgaris, the normal dosage of the bacterium concentration was 1053.9 mg/L, 95% confidence interval was [184.1,6039.5] mg/L; for Scenedesmus obliquus, it's 124.0 mg/ L, 95% confidence interval was [19.1,807.2] mg/ L.(3)For Moina Daphnia, the nitrifying bacteria agents's 24hEC₅₀ was 1.15×10²⁵mg/L, and 48hEC₅₀ was 1.00×10²² mg/L, greater than the prescribed low toxicity criteria of 100mg/L. And the logarithm concentration of Nitrifying bacteria agents had no significant linear relationship with the 24h and 48h Moina Daphnia motality.(4) The 96h zebrafish acute toxicity test showed that nitrifying bacteria agents of various concentrations had no any negative influence on zebrafish.(5) Using the E. coli and Salmonella chromogenic medium for bacteria detection, nitrifying bacteria agents didn't have these two kinds of pathogens. (6) The impact six kinds of disinfectants and antibiotics'on the activity of nitrifying bacteria was stuied, the results showed that, potassium permanganate and copper sulfate had significant inhibition of nitrifying bacteria. The 24h and 48h nitrifying bacteria concentrations for the 50% inhibitory rate were greater than the dose in aquaculture. Two kinds of antibiotics (oxytetracycline and sulfa), had the lower inhibitions on nitrifying bacteria than the four kinds of disinfectants. The dose of sulfonamides has 50% inhibition rate on nitrifying bacteria is much less than the concentration used in aquaculture system.