草鱼养殖水体中参与氮转化途径的异养菌分析

为分析草鱼池塘中参与氮代谢的异养细菌比例及其代谢途径,从杭州郊区取得4个草鱼池塘的水样,每个水样通过涂布随即挑选100株菌株进行定性显色试验,并据此选取11株异养菌进行16S rRNA序列分析。结果表明,4个草鱼养殖池塘中NH4+-N和NO2--N的平均水平分别为5.597 mg/L和0.135 mg/L。池塘中可培养的异养菌平均为3.26×105cfu/mL,其中的89.75%参与了氮的不同代谢途径,其中31.25%的氨化菌和33.50%NO3--N(NO2--N)还原菌参与了NH4+-N的生成,32.45%的氨氧化菌参与了NH4+-N的降低;NO2--N生成途径主要包括蛋白质直接转化(11.26%)、氨氧化(4.25%)和硝酸盐氮还原(10.75%),而NO2--N降低主要通过15.50%的亚硝酸氧化菌、8.75%的NO2--N还原菌和10.75%的反硝化菌实现。结果提示,草鱼养殖水体中存在大量的异养硝化菌参与不同的氮代谢途径,且产生氨氮的异养菌比例远高于去除氨氮的菌,这是草鱼养殖水体中氨氮含量易偏高的原因。同时,11株不同功能的异养菌16SrRNA鉴定结果为寡养食单胞菌(Stenotrophomonas)6株、假单胞菌(Pseudomonas)3株、克雷伯氏菌(Klebsiella)和肠杆菌(Enterobacter)各1株,而且细菌对氮源的利用具有菌株特异性。

Analysis of cultivable heterotrophic bacteria involved in nitrogen cycle in grass carp(Ctenopharyngodon idellus)pond

The aim of the present study was to detect the levels of NH⁺₄-N,NO^-₂-N and NO^-₃-N,and to determine the numbers of ammonifying,nitrifying,and denitrifying bacteria,which are responsible for the nitrogen cycling process in four representative grass carp(Ctenopharyngodon idellus)ponds.After sampling water from 4 grass carp ponds,one hundred strains selected randomly from each sample were tested by qualitative color reaction,and on the basis of the test,11 strains of heterotrophic bacteria were selected for 16S rRNA sequence analysis.Results showed that the mean levels of NH⁺₄-N and NO^-₂-N was 5.597 mg/L and 0.135 mg/L,respectively.The cultivable heterotrophic bacteria density in fish pond was 3.26×10⁵ cfu/mL and 89.75% of them were involved in nitrogen cycle,65.75% and 31% of which were involved in NH⁺₄-N production and degrading,respectively.This result indicated that the overwhelming majority of nitrite-producing bacteria resulted in high level of nitrite in grass fish pond.The identification results of 11 strains of heterotrophic bacteria were as follows:six of them were related to Stenotrophomonas,three of them were related to Pseudomonas,and the other two strains were Klebsiella and Enterobacter,respectively.Moreover,there might be strain differences on utilization of nitrogen resourses.