电缆细菌及其介导的生电硫氧化(e-SO_(x))过程研究进展

Advances in the research on cable bacteria and their mediated electrogenic sulfur oxidation(e-SO_(x))

在自然环境中,微生物参与的硫化物氧化过程是地球硫元素循环的重要组成部分,然而在多数情况下,硫化物形成于海滨等沉积物下层,而氧气等电子受体位于表层,微生物如何解决其所需的电子供体和受体不在同一空间位置的问题尚不清楚.近期研究发现,电缆细菌通过生电硫氧化(electrogenic sulfur oxidation,e-SO_(x))过程将空间分离的硫氧化反应和氧气还原反应耦合起来,完美地解决了上述问题.本文总结近10年有关电缆细菌及其介导的生电硫氧化过程的研究进展,主要包括电缆细菌生存环境、生电硫氧化生态学意义、电缆细菌的鉴定与分类、生理特征、导电结构和机制等方面.发现普遍存在于海滨沉积物、淡水沉积物、水生植物根际等环境的生电硫氧化过程可以显著影响硫、铁、碳、钙、氮、磷等元素的循环,解除硫化物毒性,强化有机污染物降解.目前已鉴定出的所有电缆细菌均属于Candidatus Electrothrix属或Candidatus Electronema属.电缆细菌通过嵌入细胞膜的高导电纤维传导电子,而且已经进化出高度故障安全的内部导电网络.建议今后继续开展电缆细菌的遗传和代谢多样性、导电结构、多细胞之间能量分配机制以及导电纤维的仿生学应用开发等方面研究,为将来应用于生物能源、生物电子和生物修复等领域提供理论和思路.

In the natural environment,the process of sulfide oxidation by microorganisms is an important part of the earth’s sulfur cycle.However,in most cases,sulfide is formed in the lower layer of sediments such as seashore,whereas the electron acceptors such as oxygen are located in the surface layer.Thus,the electron donors and receptors needed by microorganisms are not in the same spatial position,which makes it difficult to understand how electrons travel in this case.Recently,it has been found that cable bacteria can couple the sulfur oxidation reaction and oxygen reduction reaction through the process of electrogenic sulfur oxidation(e-SO_(x)),which perfectly solves the above problem.In this paper,the research progress of cable bacteria and its mediated e-SO_(x) process during the past ten years are summarized,focusing on the living environment of cable bacteria,ecological significance of e-SO_(x),identification and classification of cable bacteria,physiological characteristics,conductive structure,and mechanism.The process of e-SO_(x),which widely exists in coastal sediments,freshwater sediments,and aquatic plant rhizosphere can significantly affect the cycle of sulfur,iron,carbon,calcium,nitrogen,phosphorus and other elements,which relieves the toxicity of sulfide and strengthens the degradation of organic pollutants.At present,all the cable bacteria found belong to Candidatus electrotherix or Candidatus electronema.Cable bacteria conduct electrons through highly conductive fibers embedded in cell membranes and have evolved highly failure-safe internal conductive networks.It is suggested that the research on the genetic and metabolic diversity,conductive structure,energy distribution mechanism between cells and the application of conductive fibers should be continued in the future to provide theory and ideas for future applications in bioenergy,bioelectronics,and bioremediation.