浮萍叶面细菌群落对砷的氧化及该过程受抗生素的影响

Arsenite oxidation by phyllosphere bacterial community of duckweed and the effect of antibiotics on this process

[目的]本文旨在探讨浮萍叶面细菌群落对三价砷(AsⅢ)的氧化、对浮萍累积砷(As)的阻控作用以及抗生素对该氧化过程和阻控作用的影响。[方法]采用高效液相色谱-电感耦合等离子体-质谱(HPLC-ICP-MS)联用技术和ICP-MS测定添加110μg·L^-1 AsⅢ的有菌浮萍、有菌浮萍+抗生素(50 mg·L^-1氯霉素)、无菌浮萍处理和空白对照中溶液As形态随时间的变化情况,以及培养168 h时不同处理中浮萍As的形态以及总累积量。在培养168 h时,从培养溶液和叶面分离可培养细菌,并在纯培养条件下测定其对AsⅢ的氧化能力。[结果]与空白对照及无菌浮萍处理相比,有菌浮萍处理能够在10 h内将溶液中AsⅢ快速氧化为五价砷(AsⅤ),使溶液中的AsⅤ比例大于97.1%。有菌浮萍+抗生素处理中AsⅤ质量浓度超过AsⅢ质量浓度的时间推迟到72 h,且AsⅤ占As比例仅为70.2%。经过168 h的培养,无菌浮萍及添加氯霉素的有菌浮萍处理中累积的As总含量分别为有菌浮萍处理的3.4和2.9倍。与有菌浮萍处理相比,氯霉素显著增加浮萍中累积的AsⅢ的比例(P<0.05)。从有菌浮萍处理的浮萍叶面获得7株具有较弱AsⅢ氧化能力的细菌,这些AsⅢ氧化菌隶属于α-变形菌、β-变形菌和γ-变形菌。从有菌浮萍处理的溶液中以及有菌浮萍+抗生素处理中分离获得的细菌对AsⅢ均未表现出氧化能力。[结论]浮萍叶面细菌群落将AsⅢ快速氧化为AsⅤ的过程对累积As具有非常好的阻控作用。氯霉素显著抑制浮萍叶面细菌群落对AsⅢ的氧化,增加浮萍对As的累积以及AsⅢ在浮萍中的比例。

[Objectives]The present study was designed to investigate arsenite(AsⅢ)oxidation by phyllosphere bacterial community of duckweed,the effect of the oxidation on arsenic(As)accumulation in the duckweed and the effect of antibiotics on the processes of oxidation and accumulation.[Methods]High performance liquid chromatography inductively coupled plasma-mass spectrometry(HPLC-ICP-MS)was employed to measure the temporal speciation of As in the incubation systems of non-sterile duckweed,non-sterile duckweed supplemented with antibiotics(50 mg·L^-1 chloramphenicol),sterile duckweed and control without duckweed that contained 110μg·L^-1 AsⅢ,respectively.At 168 h,speciation and total concentration of As in duckweed from different treatments were determined by HPLC-ICP-MS and ICP-MS,respectively.Bacteria were isolated from the incubation systems at 168 h and their abilities to oxidize AsⅢwere measured by HPLC-ICP-MS.[Results]In comparison to sterile duckweed,the incubation system with non-sterile duckweed could oxidize AsⅢinto arsenate(AsⅤ)rapidly within 10 h,generating 97.1%of AsⅤin the system.The addition of chloramphenicol delayed the occurrence of AsⅤdomination in the system to 72 h,with the percentage of AsⅤat only 70.2%.After an incubation period of 168 h,total contents of As in sterile duckweed and non-sterile duckweed with chloramphenicol were 3.4 and 2.9 times of those in non-sterile duckweed,respectively.The addition of chloramphenicol significantly increased the percentage of AsⅢin the duckweed(P<0.05),compared to that in non-sterile duckweed.Seven AsⅢ-oxidizing bacteria with low oxidation ability that belonged toα-proteobacteria,β-proteobacteria andγ-proteobacteria were isolated from the phyllosphere of non-sterile duckweed.The bacteria isolated from the solution of non-sterile duckweed or from the system of non-sterile duckweed with chloramphenicol showed no oxidation of AsⅢ.[Conclusions]The rapid oxidation of AsⅢby the phyllosphere bacteria community of duckweed was effective in preventing the As accumulation in duckweed.However,chloramphenicol significantly inhibited the oxidation of AsⅢby the phyllosphere bacteria,and increased the As accumulation by the duckweed and the percentage of AsⅢin duckweed tissue.