耐汞好氧反硝化菌的鉴定及适应汞离子的特性研究

从实验室保存的高效好氧反硝化菌种中筛选得到一株抗汞细菌并命名为X1,经生理生化特性和16SrRNA基因序列分析,初步鉴定该菌为恶臭假单胞菌(Pseudomonasputida).对菌株X1进行Hg2适应特性研究,结果表明,对于Hg2浓度为2、67++4、、mg·L-1的实验组,菌体分别需要被延滞12、284018、、h后进入对数期,而8mg·L-1实验组则不能进入对数期;在好氧反硝化过程中,Hg2浓度在7mg·L+-1范围内各实验组的好氧反硝化过程中NO3-N浓度变化速率、NO2-N累积峰值、pH特征点出现时刻随着Hg2浓度的增大而增大(延迟),而Hg2浓度呈现出同硝氮一致的下降趋势,并且在对数期内除汞率能达到100%.研究表明,菌株X1对Hg2最大适宜耐受浓度为7mg·L+-1,相应适应时间约为40h.在最大耐受浓度范围内,菌株X1的生长和好氧反硝化过程呈现出"被抑制-适应-受刺激"的变化规律,其中,被抑制的时间和受刺激的程度都随着Hg2浓度的增大而增大,主要表现为延滞期的延长和对数期的缩短.此外,在对数期,菌株X1的生长速率、达到稳定期的浓度和好+氧反硝化速率也都随着Hg2浓度的增大而增大,且大于无Hg2菌组.++

Identification and Hg2+-adaptation characteristics of an aerobic denitrifying bacterium

A mercury resistant strain, X1, was screened out from efficient aerobic denitrifying bacteria. It was identified as Pseudomonas putida according to its physiological properties and the analysis of its 16S rRNA gene sequence. Study on its adaptive characteristics to Hg²⁺ showed that, for the experimental groups containing 2, 4, 6, 7 mg·L^-1 of Hg²⁺, bacteria need to be delayed for 12, 18, 28, 40 h respectively to enter the logarithmic period, with the 8mg·L^-1 group unable to enter the logarithmic period. In the process of aerobic denitrification, concentration change rate of NO₃^--N, accumulated peak of NO₂^--N and pH characteristic points had same change trend with concentration of Hg²⁺, while concentration of Hg²⁺ showed the same downward trend as NO₃^--N, and could be removed by 100% during logarithmic period. It can thus be concluded that the concentration limit was 7 mg·L^-1 and the corresponding adaptive time was 40 h. Within the concentration limit, the growth and aerobic denitrification process would present a "Suppression-adaptation-stimulation" pattern. The pent-up time and stimulated degree would both increase with the increase of Hg²⁺ concentration, which was mainly reflected by longer adapting period and shorter logarithm period. In addition, during logarithm period, its growth rate, stabilization concentration and aerobic denitrification rate also increased with the increase of Hg²⁺ concentration and were all larger than blank group.