BifA Regulates Biofilm Development of Pseudomonas putida MnB1 as a Primary Response to H2O2 and Mn2.

Yanjing Zheng,Juan Li,Hongyan Long,Dongmei Zhang,Xiaojuan Zhao,Leyong Wang,Yumei Li,Ruiyong Wang,Keke Jia,Xiancai Lu

doi:10.3389/fmicb.2018.01490

Abstract

Pseudomonas putida (P. putida) MnB1 is a widely used model strain in environment science and technology for determining microbial manganese oxidation. Numerous studies have demonstrated that the growth and metabolism of P. putida MnB1 are influenced by various environmental factors. In this study, we investigated the effects of hydrogen peroxide (H2O2) and manganese (Mn2+) on proliferation, Mn2+ acquisition, anti-oxidative system, and biofilm formation of P. putida MnB1. The related orthologs of 4 genes, mco, mntABC, sod, and bifA, were amplified from P. putida GB1 and their involvement were assayed, respectively. We found that P. putida MnB1 degraded H2O2, and quickly recovered for proliferation, but its intracellular oxidative stress state was maintained, with rapid biofilm formation after H2O2 depletion. The data from mco, mntABC, sod and bifA expression levels by qRT-PCR, elucidated a sensitivity toward bifA-mediated biofilm formation, in contrary to intracellular anti-oxidative system under H2O2 exposure. Meanwhile, Mn2+ ion supply inhibited biofilm formation of P. putida MnB1. The expression pattern of these genes showed that Mn2+ ion supply likely functioned to modulate biofilm formation rather than only acting as nutrient substrate for P. putida MnB1. Furthermore, blockade of BifA activity by GTP increased the formation and development of biofilms during H2O2 exposure, while converse response to Mn2+ ion supply was evident. These distinct cellular responses to H2O2 and Mn2+ provide insights on the common mechanism by which environmental microorganisms may be protected from exogenous factors. We postulate that BifA-mediated biofilm formation but not intracellular anti-oxidative system may be a primary protective strategy adopted by P. putida MnB1. These findings will highlight the understanding of microbial adaptation mechanisms to distinct environmental stresses.

Highlights

Environmental stresses, such as nutrient depletion, extreme temperature and pressure, high salinity, strong ultraviolet light, and radiation, commonly induce microbes to produce cellular oxidative stress with overproduction of reactive oxygen species (ROS) (Teitzel and Parsek, 2003; Matallana-Surget et al, 2009; Chattopadhyay et al, 2011; Murata et al, 2011; Chen et al, 2013)
Changes in proliferation indicated a defensive mechanism in P. putida MnB1 in response to exogenous H2O2
Since there was no significant change in proliferation of P. putida MnB1 at 40 and 200 μM of H2O2, these working concentrations were employed for the following experiments

Summary

Introduction

Environmental stresses, such as nutrient depletion, extreme temperature and pressure, high salinity, strong ultraviolet light, and radiation, commonly induce microbes to produce cellular oxidative stress with overproduction of reactive oxygen species (ROS) (Teitzel and Parsek, 2003; Matallana-Surget et al, 2009; Chattopadhyay et al, 2011; Murata et al, 2011; Chen et al, 2013). While low or moderate levels of ROS-induced physiological and biochemical changes are able to achieve an adaptation to the surrounding environment (Sies, 2017). The two primary mechanistic adaptations in response to ROS are excitation of anti-oxidative system (Apel and Hirt, 2004) and the formation of biofilms (Kubota et al, 2008). For non-pathogenic environmental microorganisms, the mechanistic basis for response to ROS (e.g., tolerance or scavenging) is less well understood

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