Endogenous hydrogen peroxide increases biofilm formation by inducing exopolysaccharide production in Acinetobacter oleivorans DR1

Abstract

In this study, we investigated differentially expressed proteins in Acinetobacter oleivorans cells during planktonic and biofilm growth by using 2-dimensional gel electrophoresis combined with matrixassisted laser desorption time-of-flight mass spectrometry. We focused on the role of oxidative stress resistance during biofilm formation using mutants defective in alkyl hydroperoxide reductase (AhpC) because its production in aged biofilms was enhanced compared to that in planktonic cells. Results obtained using an ahpC promoter-gfp reporter vector showed that aged biofilms expressed higher ahpC levels than planktonic cells at 48 h. However, at 24 h, ahpC expression was higher in planktonic cells than in biofilms. Deletion of ahpC led to a severe growth defect in rich media that was not observed in minimal media and promoted early biofilm formation through increased production of exopolysaccharide (EPS) and EPS gene expression. Increased endogenous H 2 O 2 production in the ahpC mutant in rich media enhanced biofilm formation, and this enhancement was not observed in the presence of antioxidants. Exogenous addition of H 2 O 2 promoted biofilm formation in wild type cells, which suggested that biofilm development is linked to defense against H 2 O 2 . Collectively, our data showed that EPS production caused by H 2 O 2 stress enhances biofilm formation in A. oleivorans.Many bacterial species exist in multicellular communities known as biofilms that can attach to any biotic or abiotic surface and at the interface between air and water in many different habitats 1 . The characteristics of cells within biofilms differ from those of planktonic cells. Among the biofilm-specific traits are antibiotic tolerance and resistance, slow growth, metabolic shift, production of extracellular matrix (ECM), and different cellular surface properties 2 . These physiological and phenotypical transitions result from the fine-tuned regulation of biofilm-specific genes involved in quorum sensing, the expression of small RNAs, cyclic diguanosine-5′-monophosphate (c-di-GMP) signaling, flagella biosynthesis, and ECM production 2,3,4 . The ECM is composed of exopolysaccharides, nucleic acids, and proteins, which surround biofilms and increases their tolerance to environmental chemicals 5,6 . This matrix also helps bacterial pathogens avoid host immune responses 7 . High ECM production creates a barrier that limits the penetration of various chemicals, including oxygen, nutrients, wastes, and antibiotics 8,9 . Because cells occupy different locations within a biofilm, they encounter different concentrations of chemicals, leading to heterogeneity in gene expression and physiology 2 .Nonpolar, diatomic oxygen gas is small and freely diffusible through biological membranes, which is an important characteristic for aerobic respiration, where it is used as an electron acceptor 10 . Reactive oxygen species (ROS) can be generated during either respiratory or fermentative cellular metabolism, mainly as an unavoidable consequence of electron transfer f...

Vanillic acid from Actinidia deliciosa impedes virulence in Serratia marcescens by affecting S-layer, flagellin and fatty acid biosynthesis proteins

“…Biosynthesis of purines and pyrimidines depends on the availability of histidine and DNA synthesis is linked to e-DNA release, which is also required for the biofilm formation 43 . In addition, HutU has been reported to have biofilm formation of Acinetobacter oleivorans 44 and Acinetobacter baumannii 43 . It is likely that down-regulation of HutU by vanillic acid could also be responsible for the reduction of biofilm formation in S. marcescens .…”

Non-Lethal Effects of N-Acetylcysteine on Xylella fastidiosa Strain De Donno Biofilm Formation and Detachment

“…The polysaccharide overproduction in the EPS matrix after NAC exposure could be related to the oxidative imbalance in the treated biofilm. It has been demonstrated that EPS polysaccharides played a critical role in relief of the oxygen stress in several microorganisms such as Pseudomonas putida, Sinorhizobium meliloti and Acinetobacter oleivorans [59,[64][65][66]. Indeed, some polysaccharides can scavenge hydroxyl radicals, inhibiting lipid and protein oxidation [67,68].…”

“…Indeed, some polysaccharides can scavenge hydroxyl radicals, inhibiting lipid and protein oxidation [67,68]. Interestingly, the role of the redox-sensing transcription factor OxyR in the regulation of EPS exopolysaccharide production has been reported [65,69]. Burbank and Roper [69] demonstrated that ∆oxyR mutants negatively regulated the gene expression of exopolysaccharides, making the mutants more prone to oxidative stress.…”

Lineage-specific SoxR-mediated Regulation of an Endoribonuclease Protects Non-enteric Bacteria from Redox-active Compounds

“…S4A). The genome of A. oleivorans DR1 contains exopolysaccharide (EPS) operons: poly-N-acetyl glucosamine operons and the K locus (39). The expression of genes involved in the EPS complex was increased by Ͼ3.0-fold in the sinE mutant (supplemental Fig.…”