Binding of Hg by bacterial extracellular polysaccharide: a possible role in Hg tolerance
Binding of Hg by bacterial extracellular polysaccharide: a possible role in Hg tolerance
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DOI：
10.1007/s00253-017-8239-z
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发表时间：
2017-04
影响因子：
5
通讯作者：
K. Cruz;J. Guézennec;T. Barkay
中科院分区：
文献类型：
--
作者：
K. Cruz;J. Guézennec;T. Barkay
细菌利用汞耐受性的适应机制在汞浓度升高的环境中生存。细菌产生胞外多糖（EPS）作为汞耐受机制的可能性以前尚未研究过。本研究的目的是，以确定是否细菌EPS吸附汞，如果这样做的吸附提供保护免受汞毒性。从法属波利尼西亚环礁和深海热液喷口的微生物垫细菌分离物产生的不同化学成分的纯化EPS进行了汞吸附评估。数据表明，EPS吸附高达82%的汞从溶液中，这种吸附是依赖于EPS组合物，吸附是一个饱和的机制。不同EPS的汞吸收能力范围为0.005至0.454 mmol Hg/g。为了确定EPS的产生是否会改变细菌的汞耐受性，大肠杆菌K-12菌株及其EPS缺陷突变体进行了测试，通过圆盘抑制试验。汞以剂量依赖性方式抑制生长，野生型菌株具有比各种突变体更小（约1 mm）但具有统计学显著性的抑制区，这种差异与突变体产生的EPS量相对于细胞生物量下降2倍有关。这些实验确定了colanic酸和氨基己糖作为EPS中的汞结合部分。总之，这些数据表明，汞与EPS的结合提供了对生产细菌的低水平抵抗。
Bacteria employ adaptive mechanisms of mercury (Hg) tolerance to survive in environments containing elevated Hg concentrations. The potential of extracellular polysaccharides (EPS) production by bacteria as a mechanism of Hg tolerance has not been previously investigated. The objectives of this study were to determine if bacterial EPS sorb Hg, and if so does sorption provide protection against Hg toxicity. Purified EPS with different chemical compositions produced by bacterial isolates from microbial mats in French Polynesian atolls and deep-sea hydrothermal vents were assessed for Hg sorption. The data showed that EPS sorbed up to 82% of Hg from solution, that this sorption was dependent on EPS composition, and that sorption was a saturable mechanism. Hg uptake capacities ranged from 0.005 to 0.454 mmol Hg/g for the different EPS. To determine if EPS production could alter bacterial Hg tolerance,Escherichia coliK-12 strains and their EPS defective mutants were tested by the disc inhibition assay. Mercury inhibited growth in a dose-dependent manner with wild-type strains having smaller (~1 mm), but statistically significant, zones of inhibition than various mutants and this difference was related to a 2-fold decline in the amount of EPS produced by the mutants relative to cell biomass. These experiments identified colanic acid and hexosamine as Hg-binding moieties in EPS. Together these data indicate that binding of Hg to EPS affords a low level of resistance to the producing bacteria.