兼性厌氧细菌硫化氢的产生机理及其生理功能

Endogenous production and physiological functions of hydrogen sulfide in facultative anaerobic bacteria

摘要:

硫化氢（H₂S）是继一氧化氮（NO）和一氧化碳（CO）后发现的第3种气态信号分子，但其细菌生理学研究才刚刚起步。本文根据作者对奥内达希瓦氏菌的研究，结合新近文献，就细菌的H₂S产生机理及其生理功能作了较为全面的阐述。细菌的H₂S产生途径主要有2条，一是通过降解半胱氨酸产生，二是通过厌氧呼吸产生。产生的H₂S除可为互生性微生物提供能源、供氢体和无机矿质营养外，还具有抑制竞争性微生物的生长，有效占领生态位的作用。H₂S在氧化应答中也起着重要的作用，一方面可抑制过氧化氢酶活性，增加过氧化氢对细菌的杀灭效果；另一方面可作为信号分子激活细菌的氧化应答，诱导拮抗系统的表达，保护细胞免受氧化损伤。这两种看似“矛盾”的作用与H₂S的处理时间有关：短时间处理以抑制为主，而延长处理时间则以保护为主。细菌H₂S产生机理及生理功能的阐明可为硫元素生物地球化学循环规律的揭示和感染性病原细菌的控制提供有益的参考。

Abstract:

H₂S is the third gaseous signaling molecule next to nitric oxide and carbon monoxide, but studies on its physiological functions in bacteria are just emerging. In this paper, we review recent findings regarding endogenous production and physiological functions of H₂S in facultative anaerobic bacteria, partly based on our own research on Shewanella oneidensis. There are two principal H₂S producing pathways in S. oneidensis:one is through cysteine degradation, and the other is via inorganic sulfur respiration. Endogenous H₂S could either benefit mutual growing bacteria by supplying energy and inorganic, or inhibit competing bacteria. Our review attaches particular importance to the role of H₂S in bacterial oxidative stress response. On one hand, H₂S is able to directly inhibit heme-containing catalase, enhancing killing by H₂O₂. On the other hand, H₂S could activate oxidative response as a signaling molecule, leading to cell protection from the oxidative stress due to elevated expression of H₂O₂ scavenging and repairing systems. Intriguingly, the dominance of either role is determined by H₂S-treating time, that is, inhibition is the immediate response whereas activation of oxidative stress response needs extended treatment. The elucidation of endogenous production and its physiological function of H₂S in facultative anaerobic bacteria would improve understanding of biogeochemical sulfur recycling, and facilitate control of infectious bacterial pathogens.