Delineating the Oxidative Stress Response in Shewanella Oneidensis


J Bacteriol Mycol. 2014;1(1): 2.

Delineating the Oxidative Stress Response in Shewanella Oneidensis

Jie Yuan and Haichun Gao

Institute of Microbiology, Zhejiang University, China

*Corresponding author: Haichun Gao, Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.

Received: Aug 16, 2014; Accepted: Aug 18, 2014; Published: Aug 18, 2014


Emergence of the ability to respire on O2 in prokaryotes had been a great evolutionary success story, leading way to more efficient energy use, faster growth, greater cell populations for natural selection to act upon, and eventually to the birth of higher organisms [1]. However, every coin has two sides, along with all the benefits of aerobic respiration come the Reactive Oxygen Species (ROS) and oxidative stress [2].

Superoxide (O2 -), H2O2 and Organic Peroxides (OP) are all ROS species commonly encountered by microbes [3,4]. They are damaging to DNA, RNA, protein, lipids, and virtually any cellular component, causing oxidative stress [2, 5]. The bad news is, beside radiation and other external factors, one major source of ROS is the process of aerobic respiration per se, rendering ROS an unavoidable drag of the aerobic lifestyle [1,5]. In defense, microorganisms have evolved sophisticated mechanisms to sense, respond, and battle against ROS.

Figure 1 summarizes the oxidative stress response dedicated to battling against various ROS and their damages. Although a diversity of genes are involved, and specific genes differ for different ROS species, oxidative stress response can be broadly divided into two tiers of defense. The primary defense focuses on removing the ROS (e.g., H2O2 induces catalase and peroxidase, and O2- induces superoxide dismutase), and the secondary defense is concerned with cellular component repair or removal [4,5]. Also illustrated in Figure 1 are the four major sensor-transcriptional regulators well characterized in model organisms, OxyR, PerR, OhrR, and SoxRS. As shown, each of these regulators specializes in coping with a set of different ROS species, with OxyR and PerR for H2O2 but usually found in different organisms, OhrR for OPs, and SoxRS for superoxide.

While studies in model organisms undoubtedly helped us put together a general picture of oxidative stress response, it is also of great value to expand the territory by characterizing other interesting organisms, especially those thriving in redox-stratified environments prone to ROS generation, and investigate their specific strategies. Shewanella oneidensis MR-1, a gram-negative facultative anaerobe, is such a representative. Endowed by the diverse collection of iron or heme containing respiratory proteins encoded in its genome, MR-1 is able to respire on oxygen, nitrate, Fe(III), Cr(VI) and even more exotic electron acceptors [6]. These characteristics all put MR-1 in the front seat for ROS attack [2,5], and our study aims to shed light on how this organism defends itself. We have identified analogues of OxyR and OhrR MR-1 [7,8]. And our recent research had revealed that the regulation of oxidative stress response in MR-1 (summarized in Figure 2) differ considerably from the general model shown in Figure 1.

Citation: Yuan J and Gao H. Delineating the Oxidative Stress Response in Shewanella Oneidensis. J Bacteriol Mycol. 2014;1(1): 2. ISSN: 2471-0172