土壤中砷的生物转化及砷与抗生素抗性的关联

Arsenic Biotransformation in Soils and Its Relationship with Antibiotic Resistance

砷是一种广泛存在于自然环境中毒性较强的类金属元素,农田生态系统中的植物(尤其水稻)很容易吸收积累土壤环境中的砷。植物中的砷沿食物链向高等动物传递,威胁人类健康。除土壤本身的理化性质外,土壤中砷的生物转化也强烈影响砷的生物有效性。目前研究发现异化砷酸盐(As(Ⅴ))呼吸性还原、细胞质As(Ⅴ)还原、亚砷酸盐(As(Ⅲ))氧化、As(Ⅲ)甲基化和有机砷的去甲基化在土壤砷的生物地球化学过程中起重要作用。随着分析化学和分子生物学技术的进步,最新研究发现土壤生物也参与了砷糖、砷糖磷脂、砷甜菜碱、砷代草丁膦、硫代砷等有机砷的合成,其中三价一甲基砷和砷代草丁膦可作为新型抗生素,但其合成机制及生态学功能有待进一步研究。本文还详细介绍了为适应复合污染环境微生物通过自身的进化对抗生素和重金属形成的四种共选择抗性机制:共抗性,交叉抗性、共调控和生物膜感应,特别提出了土壤中砷污染与抗生素抗性相关联这一新的研究方向。最后对砷生物转化和砷与抗生素共抗机制的未来研究方向做了展望。

Arsenic,a highly toxic metalloid,widely exists in the natural environment.Plants(especially wetland plants)can easily absorb and accumulate arsenic from the soil environment.Arsenic accumulated by plants is tranfered to animals along the food chain,and threatens human health.In addition to the physical and chemical properties of the soil,the biological transformation of arsenic in the soil heavily affects the bioavailability and fate of arsenic in soils.It has been found that dissimilatory arsenate(As(Ⅴ))-respiring reduction,cytoplasmic As(Ⅴ)reduction,arsenite(As(Ⅲ))oxidation,As(Ⅲ)methylation,and organoarsenic demethylation play important roles in biogeochemical processes of arsenic in soils.With the development of analytical chemistry and molecular biology,some recent studies have found that soil organisms are also involved in the synthesis of organoarsenic,such as arsenosuagrs,arsenosugar phospholipids,arsenobetaine,arsinothricin,and thio-arsenic.Trivalent monomethylarsenic MAs(III)and arsinothricin can be used as primordial antibiotics.However,the synthesis mechanism and ecological functions of organoarsenics need to be further investigated.In this paper,four co-selective resistance mechanisms of microorganisms to both of antibiotics and heavy metals via the evolution were introduced in details:co-resistance,crossresistance,co-regulation and biofilm induction.In particular,a new research direction of coupling arsenic pollution with antibiotic resistance in soil was put forward..In the end,the future directions of arsenic biotransformation and co-resistance mechanism to arsenic and antibiotic were prospected.