Abstract

Heavy metals bring long-term hazardous consequences and pose a serious threat to all life forms. Being non-biodegradable, they can remain in the food webs for a long period of time. Metal ions are essential for life and indispensable for almost all aspects of metabolism but can be toxic beyond threshold level to all living beings including microbes. Heavy metals are generally present in the environment, but many geogenic and anthropogenic activities has led to excess metal ion accumulation in the environment. To survive in harsh metal contaminated environments, bacteria have certain resistance mechanisms to metabolize and transform heavy metals into less hazardous forms. This also gives rise to different species of heavy metal resistant bacteria. Herein, we have tried to incorporate the different aspects of heavy metal toxicity in bacteria and provide an up-to-date and across-the-board review. The various aspects of heavy metal biology of bacteria encompassed in this review includes the biological notion of heavy metals, toxic effect of heavy metals on bacteria, the factors regulating bacterial heavy metal resistance, the diverse mechanisms governing bacterial heavy metal resistance, bacterial responses to heavy metal stress, and a brief overview of gene regulation under heavy metal stress.

摘要

重金属带来长期的危险后果，对所有生命形式构成严重威胁。由于不可生物降解，它们可以长时间留在食物网中。金属离子对生命至关重要，几乎对新陈代谢的所有方面都是必不可少的，但对包括微生物在内的所有生物的毒性可能超过阈值水平。重金属普遍存在于环境中，但许多地质和人为活动导致环境中过量的金属离子积累。为了在恶劣的金属污染环境中生存，细菌具有一定的抵抗机制来代谢重金属并将其转化为危害较小的形式。这也产生了不同种类的重金属抗性细菌。在此处，我们试图将重金属毒性的不同方面纳入细菌中，并提供最新的全面审查。本综述涵盖的细菌重金属生物学的各个方面包括重金属的生物学概念、重金属对细菌的毒性作用、调节细菌重金属抗性的因素、控制细菌重金属抗性的多种机制、细菌对重金属的反应金属胁迫，以及重金属胁迫下基因调控的简要概述。