|其他题名: ||Studies on the Ecophysiological Effects of Microcystins against Microbes|
低浓度MC-RR（0.1，1 mg/L）的处理组大肠杆菌ROS含量在整个试验过程中和对照相比均无明显变化。而高浓度MC-RR（5，10 mg/L）处理组在1 h时，细胞内ROS含量均显著高于对照，表明细胞受到了氧化胁迫，但随着处理时间的延长，处理组ROS含量逐渐下降，恢复到和对照相似的水平，说明细菌通过自身系统的适应和调节逐渐消除了细胞内的活性氧。细胞内TBARS含量变化趋势类似于ROS。高浓度MC-RR处理下，SOD、CAT和GR酶活性以及GSH含量也显著升高，随后逐渐恢复到对照水平。低浓度毒素处理下和对照无明显差异。低浓度MC-RR处理枯草芽孢杆菌1 h时细胞内SOD、CAT酶活性以及TBARS、GSH含量和对照相比无明显差异。高浓度MC-RR处理组SOD、CAT、GR酶活性以及TBARS、GSH含量均明显高于对照。10 mg/L MC-RR对枯草芽孢杆菌氧化胁迫的时间效应表明，MC-RR处理1 h时，SOD、CAT、GR酶活性以及TBARS、GSH含量均明显高于对照，但随着处理时间的延长，逐渐恢复到对照水平。
从滇池水样之中分离到了两株反硝化细菌和有机磷细菌，根据形态学和16S rDNA序列分析对其进行了鉴定。结果表明，DN-3属于Bacillus gibsonii，DN-5属于Oceanobacillus iheyensis；P-1和P-2均属于Serratia marcescens.研究结果表明，MC-RR能够抑制反硝化细菌和有机磷细菌的生长及其生理功能，并且随着浓度的增大，这种抑制效果越明显。但随着处理时间的延长，细菌逐渐抵抗了毒素的胁迫，恢复了生长，从而使处理组和对照组生长曲线均成上升趋于平行。MC-RR可能通过抑制反硝化细菌的生长和NR酶活性，从而抑制了培养液中硝态氮含量的减少、亚硝态氮含量的升高。MC-RR对有机磷细菌ACP和AKP酶活性的影响类似，具有一定的剂量抑制效应。整体来看，处理组细胞内ACP和AKP酶活性均低于对照组，说明MC-RR抑制了磷酸酶的活性。高浓度MC-RR能够显著抑制磷细菌培养液中可溶性磷酸盐含量，说明抑制了有机磷细菌的解磷能力，这种解磷能力的降低可能主要归因于对细菌数量以及磷酸酶活性的抑制。|
|英文摘要: ||In this paper the ecophysiological effects of microcystins on bacteria and its possible mechanism were studied. The main results are as follows:
1.The growth and biochemical response of E.coli and B. subtilis to MC-RR were studied. The results showed that the growth and cell viability of bacteria were inhibited for a short period compared with that of the control when exposed to MC-RR. E.coli and B. subtilis only showed growth inhibition at the initial growth phase when cells were treated with MC-RR. Indeed the normal rate of growth was gradually re-established and the growth curves of the toxin-treated and untreated bacteria became parallel. The contents of protein and soluble sugar in cells increased compared with that of the control at the beginning of MC-RR exposure and then gradually decreased. The permeabilising ability of MC-RR under different concentrations to the cell outer membrane of E. coli and B. subtilis was demonstrated by a rapid and sustained reduction in the OD675 values of lysozyme-treated cells. The extravasations of protein and soluble sugar increased with the increment of the treated-concentration of MC-RR and the prolonged of the treated-time.
2.E.coli and B. subtilis was undertaken to determine the effect of MC-RR on microbes. With high concentrations MC-RR exposure, the results showed that the ROS level and TBARS contents of E.coli were obviously increased after 1 h exposure to MC-RR. At the same time, the activities of antioxidant enzymes including SOD and CAT as well as GR activity and GSH contents in bacterial cells were also increased when exposed to microcystin –RR for 1 h, subsequently decreased. For B. subtilis, the activity of antioxidant enzymes including SOD and CAT was significantly increased than that of the control when exposed to 5 or 10 mg/L MC-RR for 1 h. The contents of TBARS and GSH as well as GR activity were obviously increased only when exposed to 10 mg/L MC-RR. For the time-effect of MC-RR on B. subtilis, the activities of antioxidant enzymes including SOD and CAT as well as GR activity and TBARS, GSH content in B. subtilis were first significantly increased and than subsequently decreased.
3.Two strains denitrifying bacteria and Organic phosphorus bacteria were isolated to further study the effect of MC-RR on the population of functional bacteria. From the morphological characteristics and results of 16S rDNA sequence analysis, the denitrifying bacteria were identified as Bacillus gibsonii and Oceanobacillus iheyensis, the organic phosphorus bacteria were identified as Serratia marcescens. The growth and denitrification function of denitrifying bacteria were prolonged by MC-RR. It showed a time- and dose-effect. The decrease of Nitrate and the increase of nitrite were both inhibited as a result of the growth and NR activity inhibition. Indeed with the toxin-treated time increased, the normal rate of growth was gradually re-established. The effect of MC-RR on organic phosphorus bacteria was similar to that on denitrifying bacteria. The enzyme activity of ACP and ALP were lower than that of the control and finally the content of phosphate in liquid medium decreased with the exposure of MC-RR.|
|Appears in Collections:||中科院水生所知识产出（2009年前）_学位论文|
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