ThecopYAZOperon Functions in Copper Efflux, Biofilm Formation, Genetic Transformation, and Stress Tolerance in Streptococcus mutans

ABSTRACTIn bacteria, copper homeostasis is closely monitored to ensure proper cellular functions while avoiding cell damage. Most Gram-positive bacteria utilize thecopYABZoperon for copper homeostasis, wherecopAandcopBencode copper-transporting P-type ATPases, whereascopYandcopZregulate the expression of thecopoperon.Streptococcus mutansis a biofilm-forming oral pathogen that harbors a putative copper-transportingcopYAZoperon. Here, we characterized the role ofcopYAZoperon in the physiology ofS. mutansand delineated the mechanisms of copper-induced toxicity in this bacterium. We observed that copper induced toxicity inS. mutanscells by generating oxidative stress and disrupting their membrane potential. Deletion of thecopYAZoperon inS. mutansstrain UA159 resulted in reduced cell viability under copper, acid, and oxidative stress relative to the viability of the wild type under these conditions. Furthermore, the ability ofS. mutansto form biofilms and develop genetic competence was impaired under copper stress. Briefly, copper stress significantly reduced cell adherence and total biofilm biomass, concomitantly repressing the transcription of thegtfB,gtfC,gtfD,gbpB, andgbpCgenes, whose products have roles in maintaining the structural and/or functional integrity of theS. mutansbiofilm. Furthermore, supplementation with copper or loss ofcopYAZresulted in significant reductions in transformability and in the transcription of competence-associated genes. Copper transport assays revealed that the ΔcopYAZstrain accrued significantly large amounts of intracellular copper compared with the amount of copper accumulation in the wild-type strain, thereby demonstrating a role for CopYAZ in the copper efflux ofS. mutans. The complementation of the CopYAZ system restored copper expulsion, membrane potential, and stress tolerance in thecopYAZ-null mutant. Taking these results collectively, we have established the function of theS. mutansCopYAZ system in copper export and have further expanded knowledge on the importance of copper homeostasis and the CopYAZ system in modulating streptococcal physiology, including stress tolerance, membrane potential, genetic competence, and biofilm formation.IMPORTANCES. mutansis best known for its role in the initiation and progression of human dental caries, one of the most common chronic diseases worldwide.S. mutansis also implicated in bacterial endocarditis, a life-threatening inflammation of the heart valve. The core virulence factors ofS. mutansinclude its ability to produce and sustain acidic conditions and to form a polysaccharide-encased biofilm that provides protection against environmental insults. Here, we demonstrate that the addition of copper and/or deletion ofcopYAZ(the copper homeostasis system) have serious implications in modulating biofilm formation, stress tolerance, and genetic transformation inS. mutans. Manipulating the pathways affected by copper and thecopYAZsystem may help to develop potential therapeutics to preventS. mutansinfection in and beyond the oral cavity.

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Roles of Four Putative DEAD-Box RNA Helicase Genes in Growth of Listeria monocytogenes EGD-e under Heat, pH, Osmotic, Ethanol, and Oxidative Stress Conditions

Applied and Environmental Microbiology ◽

10.1128/aem.01526-12 ◽

2012 ◽

Vol 78 (19) ◽

pp. 6875-6882 ◽

Cited By ~ 14

Author(s):

Annukka Markkula ◽

Miia Lindström ◽

Per Johansson ◽

Johanna Björkroth ◽

Hannu Korkeala

Keyword(s):

Oxidative Stress ◽

Listeria Monocytogenes ◽

Stress Tolerance ◽

Deletion Mutant ◽

Rna Helicase ◽

Wild Type ◽

Content Type ◽

Oxidative Stresses ◽

Dead Box ◽

Mutant Strains

ABSTRACTTo examine the role of the four putative DEAD-box RNA helicase genes ofListeria monocytogenesEGD-e in stress tolerance, the growth of the Δlmo0866, Δlmo1246, Δlmo1450, and Δlmo1722deletion mutant strains at 42.5°C, at pH 5.6 or pH 9.4, in 6% NaCl, in 3.5% ethanol, and in 5 mM H2O2was studied. Restricted growth of the Δlmo0866deletion mutant strain in 3.5% ethanol suggests that Lmo0866 contributes to ethanol stress tolerance ofL. monocytogenesEGD-e. The Δlmo1450mutant strain showed negligible growth at 42.5°C, at pH 9.4, and in 5 mM H2O2and a lower maximum growth temperature than the wild-type EGD-e, suggesting that Lmo1450 is involved in the tolerance ofL. monocytogenesEGD-e to heat, alkali, and oxidative stresses. The altered stress tolerance of the Δlmo0866and Δlmo1450deletion mutant strains did not correlate with changes in relative expression levels oflmo0866andlmo1450genes under corresponding stresses, suggesting that Lmo0866- and Lmo1450-dependent tolerance to heat, alkali, ethanol, or oxidative stress is not regulated at the transcriptional level. Growth of the Δlmo1246and Δlmo1722deletion mutant strains did not differ from that of the wild-type EGD-e under any of the conditions tested, suggesting that Lmo1246 and Lmo1722 have no roles in the growth ofL. monocytogenesEGD-e under heat, pH, osmotic, ethanol, or oxidative stress. This study shows that the putative DEAD-box RNA helicase geneslmo0866andlmo1450play important roles in tolerance ofL. monocytogenesEGD-e to ethanol, heat, alkali, and oxidative stresses.

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A Novel DNA-Binding Protein Plays an Important Role in Helicobacter pylori Stress Tolerance and Survival in the Host

Journal of Bacteriology ◽

10.1128/jb.02489-14 ◽

2014 ◽

Vol 197 (5) ◽

pp. 973-982 ◽

Cited By ~ 16

Author(s):

Ge Wang ◽

Robert J. Maier

Keyword(s):

Oxidative Stress ◽

Helicobacter Pylori ◽

Dna Binding ◽

Stress Tolerance ◽

Mutant Strain ◽

Binding Protein ◽

Dna Binding Protein ◽

Wild Type ◽

Content Type ◽

H Pylori

The gastric pathogenHelicobacter pylorimust combat chronic acid and oxidative stress. It does so via many mechanisms, including macromolecule repair and gene regulation. Mitomycin C-sensitive clones from a transposon mutagenesis library were screened. One sensitive strain contained the insertion element at the locus ofhp119, a hypothetical gene. No homologous gene exists in any (non-H. pylori) organism. Nevertheless, the predicted protein has some features characteristic of histone-like proteins, and we showed that purified HP119 protein is a DNA-binding protein. A Δhp119strain was markedly more sensitive (viability loss) to acid or to air exposure, and these phenotypes were restored to wild-type (WT) attributes upon complementation of the mutant with the wild-type version ofhp119at a separate chromosomal locus. The mutant strain was approximately10-fold more sensitive to macrophage-mediated killing than the parent or the complemented strain. Of 12 mice inoculated with the wild type, all containedH. pylori, whereas 5 of 12 mice contained the mutant strain; the mean colonization numbers were 158-fold less for the mutant strain. A proteomic (two-dimensional PAGE with mass spectrometric analysis) comparison between the Δhp119mutant and the WT strain under oxidative stress conditions revealed a number of important antioxidant protein differences; SodB, Tpx, TrxR, and NapA, as well as the peptidoglycan deacetylase PgdA, were significantly less expressed in the Δhp119mutant than in the WT strain. This study identified HP119 as a putative histone-like DNA-binding protein and showed that it plays an important role inHelicobacter pyloristress tolerance and survival in the host.

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Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

Journal of Bacteriology ◽

10.1128/jb.00813-15 ◽

2016 ◽

Vol 198 (7) ◽

pp. 1087-1100 ◽

Cited By ~ 14

Author(s):

Gursonika Binepal ◽

Kamal Gill ◽

Paula Crowley ◽

Martha Cordova ◽

L. Jeannine Brady ◽

...

Keyword(s):

Stress Tolerance ◽

Streptococcus Mutans ◽

Transport System ◽

Biofilm Formation ◽

Cellular Response ◽

Pathogenic Bacteria ◽

Transport Systems ◽

Content Type ◽

Growth And Survival ◽

Dental Biofilm

ABSTRACTPotassium (K+) is the most abundant cation in the fluids of dental biofilm. The biochemical and biophysical functions of K+and a variety of K+transport systems have been studied for most pathogenic bacteria but not for oral pathogens. In this study, we establish the modes of K+acquisition inStreptococcus mutansand the importance of K+homeostasis for its virulence attributes. TheS. mutansgenome harbors four putative K+transport systems that included two Trk-like transporters (designated Trk1 and Trk2), one glutamate/K+cotransporter (GlnQHMP), and a channel-like K+transport system (Kch). Mutants lacking Trk2 had significantly impaired growth, acidogenicity, aciduricity, and biofilm formation. [K+] less than 5 mM eliminated biofilm formation inS. mutans. The functionality of the Trk2 system was confirmed by complementing anEscherichia coliTK2420 mutant strain, which resulted in significant K+accumulation, improved growth, and survival under stress. Taken together, these results suggest that Trk2 is the main facet of the K+-dependent cellular response ofS. mutansto environment stresses.IMPORTANCEBiofilm formation and stress tolerance are important virulence properties of caries-causingStreptococcus mutans. To limit these properties of this bacterium, it is imperative to understand its survival mechanisms. Potassium is the most abundant cation in dental plaque, the natural environment ofS. mutans. K+is known to function in stress tolerance, and bacteria have specialized mechanisms for its uptake. However, there are no reports to identify or characterize specific K+transporters inS. mutans. We identified the most important system for K+homeostasis and its role in the biofilm formation, stress tolerance, and growth. We also show the requirement of environmental K+for the activity of biofilm-forming enzymes, which explains why such high levels of K+would favor biofilm formation.

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Abrogation of Neuraminidase Reduces Biofilm Formation, Capsule Biosynthesis, and Virulence of Porphyromonas gingivalis

Infection and Immunity ◽

10.1128/iai.05773-11 ◽

2011 ◽

Vol 80 (1) ◽

pp. 3-13 ◽

Cited By ~ 27

Author(s):

Chen Li ◽

Kurniyati ◽

Bo Hu ◽

Jiang Bian ◽

Jianlan Sun ◽

...

Keyword(s):

Porphyromonas Gingivalis ◽

Biofilm Formation ◽

Adult Population ◽

Transcriptional Analysis ◽

Wild Type ◽

Content Type ◽

Multiple Organs ◽

Biochemical Analyses

ABSTRACTThe oral bacteriumPorphyromonas gingivalisis a key etiological agent of human periodontitis, a prevalent chronic disease that affects up to 80% of the adult population worldwide.P. gingivalisexhibits neuraminidase activity. However, the enzyme responsible for this activity, its biochemical features, and its role in the physiology and virulence ofP. gingivalisremain elusive. In this report, we found thatP. gingivalisencodes a neuraminidase, PG0352 (SiaPg). Transcriptional analysis showed thatPG0352is monocistronic and is regulated by a sigma70-like promoter. Biochemical analyses demonstrated that SiaPgis an exo-α-neuraminidase that cleaves glycosidic-linked sialic acids. Cryoelectron microscopy and tomography analyses revealed that thePG0352deletion mutant (ΔPG352) failed to produce an intact capsule layer. Compared to the wild type,in vitrostudies showed that ΔPG352 formed less biofilm and was less resistant to killing by the host complement.In vivostudies showed that while the wild type caused a spreading type of infection that affected multiple organs and all infected mice were killed, ΔPG352 only caused localized infection and all animals survived. Taken together, these results demonstrate that SiaPgis an important virulence factor that contributes to the biofilm formation, capsule biosynthesis, and pathogenicity ofP. gingivalis, and it can potentially serve as a new target for developing therapeutic agents againstP. gingivalisinfection.

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Two regulatory factors of Vibrio cholerae activating the mannose-sensitive haemagglutinin pilus expression is important for biofilm formation and colonization in mice

Microbiology ◽

10.1099/mic.0.001098 ◽

2021 ◽

Vol 167 (10) ◽

Author(s):

Mengting Shi ◽

Yue Zheng ◽

Xianghong Wang ◽

Zhengjia Wang ◽

Menghua Yang

Keyword(s):

Mouse Model ◽

Vibrio Cholerae ◽

Biofilm Formation ◽

Type Species ◽

Wild Type ◽

Expression Library ◽

Content Type ◽

Genomic Expression ◽

Infant Mouse ◽

Link Type

Vibrio cholerae the causative agent of cholera, uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host intestine, which is its preferred colonization site. Transcription of the mannose-sensitive haemagglutinin pilus (MSHA), which aids the persistence of V. cholerae in aquatic environments, but causes its clearance by host immune defenses, was found to be regulated by a yet unknown mechanism during the infection cycle of V. cholerae . In this study, genomic expression library screening revealed that two regulators, VC1371 and VcRfaH, are able to positively activate the transcription of MSHA operon. VC1371 is localized and active in the cell membrane. Deletion of vc1371 or VcrfaH genes in V. cholerae resulted in less MshA protein production and less efficiency of biofilm formation compared to that in the wild-type strain. An adult mouse model showed that the mutants with vc1371 or VcrfaH deletion colonized less efficiently than the wild-type; the VcrfaH deletion mutant showed less colonization efficiency in the infant mouse model. The findings strongly suggested that the two regulators, namely VC1371 and VcRfaH, which are involved in the regulation of MSHA expression, play an important role in V. cholerae biofilm formation and colonization in mice.

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Oxidative Stressors Modify the Response of Streptococcus mutans to Its Competence Signal Peptides

Applied and Environmental Microbiology ◽

10.1128/aem.01345-17 ◽

2017 ◽

Vol 83 (22) ◽

Cited By ~ 9

Author(s):

Matthew De Furio ◽

Sang Joon Ahn ◽

Robert A. Burne ◽

Stephen J. Hagen

Keyword(s):

Oxidative Stress ◽

Reactive Oxygen Species ◽

Dental Caries ◽

Signaling Pathway ◽

Streptococcus Mutans ◽

Reactive Oxygen ◽

Oxygen Species ◽

Oral Biofilm ◽

Genetic Competence ◽

Content Type

ABSTRACTThe dental caries pathogenStreptococcus mutansis continually exposed to several types of stress in the oral biofilm environment. Oxidative stress generated by reactive oxygen species has a major impact on the establishment, persistence, and virulence ofS. mutans. Here, we combined fluorescent reporter-promoter fusions with single-cell imaging to study the effects of reactive oxygen species on activation of genetic competence inS. mutans. Exposure to paraquat, which generates superoxide anion, produced a qualitatively different effect on activation of expression of the gene for the master competence regulator, ComX, than did treatment with hydrogen peroxide (H2O2), which can yield hydroxyl radical. Paraquat suppressed peptide-mediated induction ofcomXin a progressive and cumulative fashion, whereas the response to H2O2displayed a strong threshold behavior. Low concentrations of H2O2had little effect on induction ofcomXor the bacteriocin genecipB, but expression of these genes declined sharply if extracellular H2O2exceeded a threshold concentration. These effects were not due to decreased reporter gene fluorescence. Two different threshold concentrations were observed in the response to H2O2, depending on the gene promoter that was analyzed and the pathway by which the competence regulon was stimulated. The results show that paraquat and H2O2affect theS. mutanscompetence signaling pathway differently, and that some portions of the competence signaling pathway are more sensitive to oxidative stress than others.IMPORTANCEStreptococcus mutansinhabits the oral biofilm, where it plays an important role in the development of dental caries. Environmental stresses such as oxidative stress influence the growth ofS. mutansand its important virulence-associated behaviors, such as genetic competence.S. mutanscompetence development is a complex behavior that involves two different signaling peptides and can exhibit cell-to-cell heterogeneity. Although oxidative stress is known to influenceS. mutanscompetence, it is not understood how oxidative stress interacts with the peptide signaling or affects heterogeneity. In this study, we used fluorescent reporters to probe the effect of reactive oxygen species on competence signaling at the single-cell level. Our data show that different reactive oxygen species have different effects onS. mutanscompetence, and that some portions of the signaling pathway are more acutely sensitive to oxidative stress than others.

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Effect of Nitroxides on Swarming Motility and Biofilm Formation, Multicellular Behaviors in Pseudomonas aeruginosa

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01381-13 ◽

2013 ◽

Vol 57 (10) ◽

pp. 4877-4881 ◽

Cited By ~ 45

Author(s):

César de la Fuente-Núñez ◽

Fany Reffuveille ◽

Kathryn E. Fairfull-Smith ◽

Robert E. W. Hancock

Keyword(s):

Nitric Oxide ◽

Pseudomonas Aeruginosa ◽

Biofilm Formation ◽

Wild Type ◽

Planktonic Cells ◽

Swarming Motility ◽

Content Type ◽

Exogenous Addition ◽

Biofilm Dispersion ◽

Dispersal Activity

ABSTRACTThe ability of nitric oxide (NO) to induce biofilm dispersion has been well established. Here, we investigated the effect of nitroxides (sterically hindered nitric oxide analogues) on biofilm formation and swarming motility inPseudomonas aeruginosa. A transposon mutant unable to produce nitric oxide endogenously (nirS) was deficient in swarming motility relative to the wild type and the complemented strain. Moreover, expression of thenirSgene was upregulated by 9.65-fold in wild-type swarming cells compared to planktonic cells. Wild-type swarming levels were substantially restored upon the exogenous addition of nitroxide containing compounds, a finding consistent with the hypothesis that NO is necessary for swarming motility. Here, we showed that nitroxides not only mimicked the dispersal activity of NO but also prevented biofilms from forming in flow cell chambers. In addition, anirStransposon mutant was deficient in biofilm formation relative to the wild type and the complemented strain, thus implicating NO in the formation of biofilms. Intriguingly, despite its stand-alone action in inhibiting biofilm formation and promoting dispersal, a nitroxide partially restored the ability of anirSmutant to form biofilms.

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Motility-Independent Formation of Antibiotic-TolerantPseudomonas aeruginosaAggregates

Applied and Environmental Microbiology ◽

10.1128/aem.00844-19 ◽

2019 ◽

Vol 85 (14) ◽

Cited By ~ 3

Author(s):

Sally Demirdjian ◽

Hector Sanchez ◽

Daniel Hopkins ◽

Brent Berwin

Keyword(s):

Biofilm Formation ◽

Bacterial Pathogen ◽

Aggregate Formation ◽

Flagellar Motility ◽

Wild Type ◽

Chronic Infections ◽

Content Type ◽

Temporal Adaptation ◽

Bacterial Aggregates

ABSTRACTPseudomonas aeruginosais a bacterial pathogen that causes severe chronic infections in immunocompromised individuals. This bacterium is highly adaptable to its environments, which frequently select for traits that promote bacterial persistence. A clinically significant temporal adaptation is the formation of surface- or cell-adhered bacterial biofilms that are associated with increased resistance to immune and antibiotic clearance. Extensive research has shown that bacterial flagellar motility promotes formation of such biofilms, whereupon the bacteria subsequently become nonmotile. However, recent evidence shows that antibiotic-tolerant nonattached bacterial aggregates, distinct from surface-adhered biofilms, can form, and these have been reported in the context of lung infections, otitis media, nonhealing wounds, and soft tissue fillers. It is unclear whether the same bacterial traits are required for aggregate formation as for biofilm formation. In this report, using isogenic mutants, we demonstrate thatP. aeruginosaaggregates in liquid cultures are spontaneously formed independent of bacterial flagellar motility and independent of an exogenous scaffold. This contrasts with the role of the flagellum to initiate surface-adhered biofilms. Similarly to surface-attached biofilms, these aggregates exhibit increased antibiotic tolerance compared to planktonic cultures. These findings provide key insights into the requirements for aggregate formation that contrast with those for biofilm formation and that may have relevance for the persistence and dissemination of nonmotile bacteria found within chronic clinical infections.IMPORTANCEIn this work, we have investigated the role of bacterial motility with regard to antibiotic-tolerant bacterial aggregate formation. Previous work has convincingly demonstrated thatP. aeruginosaflagellar motility promotes the formation of surface-adhered biofilms in many systems. In contrast, aggregate formation byP. aeruginosawas observed for nonmotile but not for motile cells in the presence of an exogenous scaffold. Here, we demonstrate that both wild-typeP. aeruginosaand mutants that genetically lack motility spontaneously form antibiotic-tolerant aggregates in the absence of an exogenously added scaffold. Additionally, we also demonstrate that wild-type (WT) and nonmotileP. aeruginosabacteria can coaggregate, shedding light on potential physiological interactions and heterogeneity of aggregates.

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Role of Flagellin-Homologous Proteins in Biofilm Formation by Pathogenic Vibrio Species

mBio ◽

10.1128/mbio.01793-19 ◽

2019 ◽

Vol 10 (4) ◽

Cited By ~ 2

Author(s):

You-Chul Jung ◽

Mi-Ae Lee ◽

Kyu-Ho Lee

Keyword(s):

Biofilm Formation ◽

Specific Binding ◽

Biological Significance ◽

Wild Type ◽

Forming Process ◽

Homologous Proteins ◽

Content Type ◽

Pathogenic Vibrio ◽

Biofilm Matrix

ABSTRACT The pathogenic bacterium Vibrio vulnificus exhibits the ability to form biofilm, for which initiation is dependent upon swimming motility by virtue of a polar flagellum. The filament of its flagellum is composed of multiple flagellin subunits, FlaA, -B, -C, and -D. In V. vulnificus genomes, however, open reading frames (ORFs) annotated by FlaE and -F are also present. Although neither FlaE nor FlaF is involved in filament formation and cellular motility, they are well expressed and secreted to the extracellular milieu through the secretion apparatus for flagellar assembly. In the extrapolymeric matrix of V. vulnificus biofilm, significant levels of FlaEF were detected. Mutants defective in both flaE and flaF formed significantly decreased biofilms compared to the wild-type biofilm. Thus, the potential role of FlaEF during the biofilm-forming process was investigated by exogenous addition of recombinant FlaEF (rFlaEF) to the biofilm assays. The added rFlaE and rFlaF were predominantly incorporated into the biofilm matrix formed by the wild type. However, biofilms formed by a mutant defective in exopolysaccharide (EPS) biosynthesis were not affected by added FlaEF. These results raised a possibility that FlaEF specifically interact with EPS within the biofilm matrix. In vitro pulldown assays using His-tagged rFlaEF or rFlaC revealed the specific binding of EPS to rFlaEF but not to rFlaC. Taken together, our results demonstrate that V. vulnificus FlaEF, flagellin-homologous proteins (FHPs), are crucial for biofilm formation by directly interacting with the essential determinant for biofilm maturation, EPS. Further analyses performed with other pathogenic Vibrio species demonstrated both the presence of FHPs and their important role in biofilm formation. IMPORTANCE Flagellar filaments of the pathogenic Vibrio species, including V. vulnificus, V. parahaemolyticus, and V. cholerae, are composed of multiple flagellin subunits. In their genomes, however, there are higher numbers of the ORFs encoding flagellin-like proteins than the numbers of flagellin subunits required for filament assembly. Since these flagellin-homologous proteins (FHPs) are well expressed and excreted to environments via a flagellin transport channel, their extracellular role in the pathogenic Vibrio has been enigmatic. Their biological significance, which is not related with flagellar functions, has been revealed to be in maturation of biofilm structures. Among various components of the extracellular polymeric matrix produced in the V. vulnificus biofilms, the exopolysaccharides (EPS) are dominant constituents and crucial in maturation of biofilms. The enhancing role of the V. vulnificus FHPs in biofilm formation requires the presence of EPS, as indicated by highly specific interactions among two FHPs and three EPS.

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SodA Contributes to the Virulence of Avian PathogenicEscherichia coliO2 Strain E058 in Experimentally Infected Chickens

Journal of Bacteriology ◽

10.1128/jb.00625-18 ◽

2019 ◽

Vol 201 (6) ◽

Cited By ~ 1

Author(s):

Qingqing Gao ◽

Le Xia ◽

Xiaobo Wang ◽

Zhengqin Ye ◽

Jinbiao Liu ◽

...

Keyword(s):

Oxidative Stress ◽

Escherichia Coli ◽

Hydrogen Peroxide ◽

Virulence Factor ◽

Infection Process ◽

Strain Identification ◽

Bacterial Disease ◽

Wild Type ◽

Content Type

ABSTRACTStrains of avian pathogenicEscherichia coli(APEC), the common pathogen of avian colibacillosis, encounter reactive oxygen species (ROS) during the infection process. Superoxide dismutases (SODs), acting as antioxidant factors, can protect against ROS-mediated host defenses. Our previous reports showed that thesodAgene (encoding a Mn-cofactor-containing SOD [MnSOD]) is highly expressed during the septicemic infection process of APEC.sodAhas been proven to be a virulence factor of certain pathogens, but its role in the pathogenicity of APEC has not been fully identified. In this study, we deleted thesodAgene from the virulent APEC O2 strain E058 and examined thein vitroandin vivophenotypes of the mutant. ThesodAmutant was more sensitive to hydrogen peroxide in terms of both its growth and viability than was the wild type. The ability to form a biofilm was weakened in thesodAmutant. ThesodAmutant was significantly more easily phagocytosed by chicken macrophages than was the wild-type strain. Chicken infection assays revealed significantly attenuated virulence of thesodAmutant compared with the wild type at 24 h postinfection. The virulence phenotype was restored by complementation of thesodAgene. Quantitative real-time reverse transcription-PCR revealed that the inactivation ofsodAreduced the expression of oxidative stress response geneskatE,perR, andosmCbut did not affect the expression ofsodBandsodC. Taken together, our studies indicate that SodA is important for oxidative resistance and virulence of APEC E058.IMPORTANCEAvian colibacillosis, caused by strains of avian pathogenicEscherichia coli, is a major bacterial disease of severe economic significance to the poultry industry worldwide. The virulence mechanisms of APEC are not completely understood. This study investigated the influence of an antioxidant protein, SodA, on the phenotype and pathogenicity of APEC O2 strain E058. This is the first report demonstrating that SodA plays an important role in protecting a specific APEC strain against hydrogen peroxide-induced oxidative stress and contributes to the virulence of this pathotype strain. Identification of this virulence factor will enhance our knowledge of APEC pathogenic mechanisms, which is crucial for designing successful strategies against associated infections and transmission.

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