scholarly journals Characterization of BcaA, a Putative Classical Autotransporter Protein in Burkholderia pseudomallei

2013 ◽  
Vol 81 (4) ◽  
pp. 1121-1128 ◽  
Author(s):  
Cristine G. Campos ◽  
Luke Borst ◽  
Peggy A. Cotter
Keyword(s):  
Burkholderia Pseudomallei ◽  
Efflux Pump ◽  
Outer Membrane Proteins ◽  
Lung Epithelial Cells ◽  
Wild Type ◽  
Passenger Domain ◽  
Content Type ◽  
Reading Frame ◽  
Type V

ABSTRACTBurkholderia pseudomalleiis a tier 1 select agent, and the causative agent of melioidosis, a disease with effects ranging from chronic abscesses to fulminant pneumonia and septic shock, which can be rapidly fatal. Autotransporters (ATs) are outer membrane proteins belonging to the type V secretion system family, and many have been shown to play crucial roles in pathogenesis. The open reading frame Bp1026b_II1054 (bcaA) inB. pseudomalleistrain 1026b is predicted to encode a classical autotransporter protein with an approximately 80-kDa passenger domain that contains a subtilisin-related domain. Immediately 3′ tobcaAis Bp11026_II1055 (bcaB), which encodes a putative prolyl 4-hydroxylase. To investigate the role of these genes in pathogenesis, large in-frame deletion mutations ofbcaAandbcaBwere constructed in strain Bp340, an efflux pump mutant derivative of the melioidosis clinical isolate 1026b. Comparison of Bp340ΔbcaAand Bp340ΔbcaBmutants to wild-typeB. pseudomalleiin vitrodemonstrated similar levels of adherence to A549 lung epithelial cells, but the mutant strains were defective in their ability to invade these cells and to form plaques. In a BALB/c mouse model of intranasal infection, similar bacterial burdens were observed after 48 h in the lungs and liver of mice infected with Bp340ΔbcaA, Bp340ΔbcaB, and wild-type bacteria. However, significantly fewer bacteria were recovered from the spleen of Bp340ΔbcaA-infected mice, supporting the idea of a role for this AT in dissemination or in survival in the passage from the site of infection to the spleen.

scholarly journals Characterization of New Virulence Factors Involved in the Intracellular Growth and Survival of Burkholderia pseudomallei

2015 ◽  
Vol 84 (3) ◽  
pp. 701-710 ◽  
Author(s):  
Madeleine G. Moule ◽  
Natasha Spink ◽  
Sam Willcocks ◽  
Jiali Lim ◽  
José Afonso Guerra-Assunção ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Insertion Site ◽  
Wild Type ◽  
Content Type ◽  
Growth And Survival ◽  
New Genes ◽  
Insertion Sites

Burkholderia pseudomallei, the causative agent of melioidosis, has complex and poorly understood extracellular and intracellular lifestyles. We used transposon-directed insertion site sequencing (TraDIS) to retrospectively analyze a transposon library that had previously been screened through a BALB/c mouse model to identify genes important for growth and survivalin vivo. This allowed us to identify the insertion sites and phenotypes of negatively selected mutants that were previously overlooked due to technical constraints. All 23 unique genes identified in the original screen were confirmed by TraDIS, and an additional 105 mutants with various degrees of attenuationin vivowere identified. Five of the newly identified genes were chosen for further characterization, and clean, unmarkedbpsl2248,tex,rpiR,bpsl1728, andbpss1528deletion mutants were constructed from the wild-type strain K96243. Each of these mutants was testedin vitroandin vivoto confirm their attenuated phenotypes and investigate the nature of the attenuation. Our results confirm that we have identified new genes important toin vivovirulence with roles in different stages ofB. pseudomalleipathogenesis, including extracellular and intracellular survival. Of particular interest, deletion of the transcription accessory protein Tex was shown to be highly attenuating, and thetexmutant was capable of providing protective immunity against challenge with wild-typeB. pseudomallei, suggesting that the genes identified in our TraDIS screen have the potential to be investigated as live vaccine candidates.

scholarly journals Involvement of the AcrAB-TolC Efflux Pump in the Resistance, Fitness, and Virulence of Enterobacter cloacae

2012 ◽  
Vol 56 (4) ◽  
pp. 2084-2090 ◽  
Author(s):  
Astrid Pérez ◽  
Margarita Poza ◽  
Ana Fernández ◽  
Maria del Carmen Fernández ◽  
Susana Mallo ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Efflux Pump ◽  
Enterobacter Cloacae ◽  
Efflux Pumps ◽  
Clinical Isolates ◽  
Wild Type ◽  
Content Type

ABSTRACTMultidrug efflux pumps have emerged as important mechanisms of antimicrobial resistance in bacterial pathogens. In order to cause infection, pathogenic bacteria require mechanisms to avoid the effects of host-produced compounds, and express efflux pumps may accomplish this task. In this study, we evaluated the effect of the inactivation of AcrAB-TolC on antimicrobial resistance, fitness, and virulence inEnterobacter cloacae, an opportunistic pathogen usually involved in nosocomial infections. Two different clinical isolates ofE. cloacaewere used, EcDC64 (multidrug resistance overexpressing the AcrAB-TolC efflux pump) and Jc194 (basal AcrAB-TolC expression). TheacrAandtolCgenes were deleted in strains EcDC64 and Jc194 to produce, respectively, EcΔacrAand EcΔtolCand JcΔacrAand JcΔtolCknockout (KO) derivatives. Antibiotic susceptibility testing was performed with all isolates, and we discovered that these mechanisms are involved in the resistance ofE. cloacaeto several antibiotics. Competition experiments were also performed with wild-type and isogenic KO strains. The competition index (CI), defined as the mutant/wild-type ratio, revealed that theacrAandtolCgenes both affect the fitness ofE. cloacae, as fitness was clearly reduced in theacrAandtolCKO strains. The median CI values obtainedin vitroandin vivowere, respectively, 0.42 and 0.3 for EcDC64/EcΔacrA, 0.24 and 0.38 for EcDC64/EcΔtolC, 0.15 and 0.11 for Jc194/JcΔacrA, and 0.38 and 0.39 for Jc194/JcΔtolC. Use of an intraperitoneal mouse model of systemic infection revealed reduced virulence in bothE. cloacaeclinical strains when either theacrAortolCgene was inactivated. In conclusion, the structural components of the AcrAB-TolC efflux pump appear to play a role in antibiotic resistance as well as environmental adaptation and host virulence in clinical isolates ofE. cloacae.

scholarly journals Manogepix (APX001A) In Vitro Activity against Candida auris: Head-to-Head Comparison of EUCAST and CLSI MICs

2020 ◽  
Vol 64 (10) ◽  
Author(s):  
Maiken Cavling Arendrup ◽  
Anuradha Chowdhary ◽  
Karin Meinike Jørgensen ◽  
Joseph Meletiadis
Keyword(s):  
Efflux Pump ◽  
Absolute Difference ◽  
Low Grade ◽  
Wild Type ◽  
Candida Auris ◽  
Content Type ◽  
New Class ◽  
Active Moiety ◽  
Upper Limits

ABSTRACT Fosmanogepix is a novel prodrug in a new class of antifungal agents. Manogepix is the active moiety. We evaluated the CLSI and EUCAST MICs of manogepix and eight comparators against Candida auris. CLSI M27-A3 susceptibility testing of manogepix was performed for 122 C. auris isolates and compared to CLSI and EUCAST MICs for manogepix and eight comparators. Differences and agreement were calculated for each compound. Wild-type upper limits (WT-ULs; the upper MIC where the wild-type distribution ends) for manogepix and correlations with other drugs’ MICs were determined. Manogepix MICs (CLSI/EUCAST [mg/liter]) and WT-ULs were as follows: MIC50s, 0.008/0.016; MIC90s, 0.03/0.03; ranges, 0.001 to 0.25/0.001 to 0.125; 97.5% and 99% WT-ULs, 0.03/0.125 and 0.06/0.125, respectively. The manogepix CLSI/EUCAST MIC distributions spanned 9/8 dilutions, respectively. Significant correlation was found for all azoles, particularly fluconazole (r = 0.22 to 0.74, P < 0.05). Isolates with EUCAST manogepix MICs of ≤0.004 had 7.6-/10.2-fold-lower fluconazole CLSI/EUCAST MICs than the remaining isolates that had higher manogepix MICs. The highest essential agreement between CLSI and EUCAST results was observed for manogepix and fluconazole, with a median difference of −1 to 0 2-fold dilutions, 90th percentile absolute difference of 1, and 90 to 92% and 98 to 100% agreement within ±1 and ±2 dilutions. The lowest agreements within ±1 and ±2 dilutions were found for isavuconazole and anidulafungin (44 to 50% and 69 to 76%). The correlation between CLSI and EUCAST manogepix MICs against C. auris was excellent. Differential MICs were found, and these correlated with fluconazole MICs, suggesting that the C. auris population is a mix of wild-type isolates and non-wild-type isolates with low-grade manogepix MIC elevation, probably involving efflux pump expression. However, manogepix was the most potent agent against C. auris in this in vitro study.

scholarly journals Mutations Reducing In Vitro Susceptibility to Novel LpxC Inhibitors in Pseudomonas aeruginosa and Interplay of Efflux and Nonefflux Mechanisms

2019 ◽  
Vol 64 (1) ◽  
Author(s):  
Adriana K. Jones ◽  
Ruth E. Caughlan ◽  
Angela L. Woods ◽  
Kyoko Uehara ◽  
Lili Xie ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Single Step ◽  
Protein Overexpression ◽  
Wild Type ◽  
Novel Mutations ◽  
In Vitro Susceptibility ◽  
Content Type ◽  
Selection Experiments ◽  
Step Selection

ABSTRACT Upregulated expression of efflux pumps, lpxC target mutations, LpxC protein overexpression, and mutations in fabG were previously shown to mediate single-step resistance to the LpxC inhibitor CHIR-090 in P. aeruginosa. Single-step selection experiments using three recently described LpxC inhibitors (compounds 2, 3, and 4) and mutant characterization showed that these mechanisms affect susceptibility to additional novel LpxC inhibitors. Serial passaging of P. aeruginosa wild-type and efflux pump-defective strains using the LpxC inhibitor CHIR-090 or compound 1 generated substantial shifts in susceptibility and underscored the interplay of efflux and nonefflux mechanisms. Whole-genome sequencing of CHIR-090 passage mutants identified efflux pump overexpression, fabG mutations, and novel mutations in fabF1 and in PA4465 as determinants of reduced susceptibility. Two new lpxC mutations, encoding A214V and G208S, that reduce susceptibility to certain LpxC inhibitors were identified in these studies, and we show that these and other target mutations differentially affect different LpxC inhibitor scaffolds. Lastly, the combination of target alteration (LpxCA214V) and upregulated expression of LpxC was shown to be tolerated in P. aeruginosa and could mediate significant decreases in susceptibility.

scholarly journals The Burkholderia pseudomallei ΔasdMutant Exhibits Attenuated Intracellular Infectivity and Imparts Protection against Acute Inhalation Melioidosis in Mice

2011 ◽  
Vol 79 (10) ◽  
pp. 4010-4018 ◽  
Author(s):  
Michael H. Norris ◽  
Katie L. Propst ◽  
Yun Kang ◽  
Steven W. Dow ◽  
Herbert P. Schweizer ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Cell Model ◽  
Single Copy ◽  
Wild Type ◽  
Live Attenuated Vaccine ◽  
Content Type ◽  
Life Threatening ◽  
A Cell ◽  
Bioterrorism Agent

ABSTRACTBurkholderia pseudomallei, the cause of serious and life-threatening diseases in humans, is of national biodefense concern because of its potential use as a bioterrorism agent. This microbe is listed as a select agent by the CDC; therefore, development of vaccines is of significant importance. Here, we further investigated the growth characteristics of a recently createdB. pseudomallei1026b Δasdmutantin vitro, in a cell model, and in an animal model of infection. The mutant was typified by an inability to grow in the absence of exogenous diaminopimelate (DAP); upon single-copy complementation with a wild-type copy of theasdgene, growth was restored to wild-type levels. Further characterization of theB. pseudomalleiΔasdmutant revealed a marked decrease in RAW264.7 murine macrophage cytotoxicity compared to the wild type and the complemented Δasdmutant. RAW264.7 cells infected by the Δasdmutant did not exhibit signs of cytopathology or multinucleated giant cell (MNGC) formation, which were observed in wild-typeB. pseudomalleicell infections. The Δasdmutant was found to be avirulent in BALB/c mice, and mice vaccinated with the mutant were protected against acute inhalation melioidosis. Thus, theB. pseudomalleiΔasdmutant may be a promising live attenuated vaccine strain and a biosafe strain for consideration of exclusion from the select agent list.

scholarly journals Palmitoylation State Impacts Induction of Innate and Acquired Immunity by the Salmonella enterica Serovar TyphimuriummsbBMutant

2011 ◽  
Vol 79 (12) ◽  
pp. 5027-5038 ◽  
Author(s):  
Qingke Kong ◽  
David A. Six ◽  
Qing Liu ◽  
Lillian Gu ◽  
Kenneth L. Roland ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Lipid A ◽  
Inflammatory Responses ◽  
Outer Membrane Proteins ◽  
Acyl Chain ◽  
Wild Type ◽  
Proinflammatory Response ◽  
Content Type ◽  
Serovar Typhimurium

ABSTRACTLipopolysaccharide (LPS), composed of lipid A, core, and O-antigen, is a major virulence factor ofSalmonella entericaserovar Typhimurium, with lipid A being a major stimulator to induce the proinflammatory response via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. WhileSalmonella msbBmutants lacking the myristate chain in lipid A were investigated widely as an anticancer vaccine, inclusion of themsbBmutation in aSalmonellavaccine to deliver heterologous antigens has not yet been investigated. We introduced themsbBmutation alone or in combination with mutations in other lipid A acyl chain modification genes encoding PagL, PagP, and LpxR into wild-typeS. entericaserovar Typhimurium. ThemsbBmutation reduced virulence, while thepagL,pagP, andlpxRmutations did not affect virulence in themsbBmutant background when administered orally to BALB/c mice. Also, all mutants exhibited sensitivity to polymyxin B but did not display sensitivity to deoxycholate. LPS derived frommsbBmutants induced less inflammatory responses in human Mono Mac 6 and murine macrophage RAW264.7 cellsin vitro. However, anmsbBmutant did not decrease the induction of inflammatory responses in mice compared to the levels induced by the wild-type strain, whereas anmsbB pagPmutant induced less inflammatory responsesin vivo. The mutations were moved to an attenuatedSalmonellavaccine strain to evaluate their effects on immunogenicity. Lipid A modification caused by themsbBmutation alone and in combination withpagL,pagP, andlpxRmutations led to higher IgA production in the vaginal tract but still retained the same IgG titer level in serum to PspA, a test antigen fromStreptococcus pneumoniae, and to outer membrane proteins (OMPs) fromSalmonella.

scholarly journals Mechanisms DecreasingIn VitroSusceptibility to the LpxC Inhibitor CHIR-090 in the Gram-Negative Pathogen Pseudomonas aeruginosa

2011 ◽  
Vol 56 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Ruth E. Caughlan ◽  
Adriana K. Jones ◽  
Angela M. DeLucia ◽  
Angela L. Woods ◽  
Lili Xie ◽  
...  
Keyword(s):  
Target Gene ◽  
Efflux Pump ◽  
Acid Synthesis ◽  
Growth Defect ◽  
Regulator Gene ◽  
Wild Type ◽  
Gram Negative ◽  
Content Type ◽  
Repressor Gene

ABSTRACTTestingP. aeruginosaefflux pump mutants showed that the LpxC inhibitor CHIR-090 is a substrate for MexAB-OprM, MexCD-OprJ, and MexEF-OprN. UtilizingP. aeruginosaPAO1 with a chromosomalmexC::luxCDABEfusion, luminescent mutants arose on medium containing 4 μg/ml CHIR-090, indicating upregulation of MexCD-OprJ. These mutants were less susceptible to CHIR-090 (MIC, 4 μg/ml) and had mutations in themexCD-oprJrepressor genenfxB. Nonluminescent mutants (MIC, 4 μg/ml) that had mutations in themexAB-oprMregulator genemexRwere also observed. Plating the clinical isolate K2153 on 4 μg/ml CHIR-090 selected mutants with alterations inmexS(immediately upstream ofmexT), which upregulates MexEF-OprN. A mutant altered in the putative1ribosomal binding site (RBS) upstream oflpxCand overexpressing LpxC was selected on a related LpxC inhibitor and exhibited reduced susceptibility to CHIR-090. Overexpression of LpxC from a plasmid reduced susceptibility to CHIR-090, and introduction of the altered RBS in this construct further increased expression of LpxC and decreased susceptibility to CHIR-090. Using amutS(hypermutator) strain, a mutant with an alteredlpxCtarget gene (LpxC L18V) was also selected. Purified LpxC L18V had activity similar to that of wild-type LpxC in anin vitroassay but had reduced inhibition by CHIR-090. Finally, an additional class of mutant, typified by an extreme growth defect, was identified. These mutants had mutations infabG, indicating that alteration in fatty acid synthesis conferred resistance to LpxC inhibitors. Passaging experiments showed progressive decreases in susceptibility to CHIR-090. Therefore,P. aeruginosacan employ several strategies to reduce susceptibility to CHIR-090in vitro.

scholarly journals The Xanthomonas oryzae pv. oryzae PilZ Domain Proteins Function Differentially in Cyclic di-GMP Binding and Regulation of Virulence and Motility

2015 ◽  
Vol 81 (13) ◽  
pp. 4358-4367 ◽  
Author(s):  
Fenghuan Yang ◽  
Fang Tian ◽  
Huamin Chen ◽  
William Hutchins ◽  
Ching-Hong Yang ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Bacterial Blight ◽  
Pathogenic Bacteria ◽  
Xanthomonas Oryzae ◽  
Wild Type ◽  
Binding Motifs ◽  
Content Type ◽  
Reading Frame ◽  
Bacterial Blight Pathogen

ABSTRACTThe PilZ domain proteins have been demonstrated to be one of the major types of receptors mediating cyclic di-GMP (c-di-GMP) signaling pathways in several pathogenic bacteria. However, little is known about the function of PilZ domain proteins in c-di-GMP regulation of virulence in the bacterial blight pathogen of riceXanthomonas oryzaepv. oryzae. Here, the roles of PilZ domain proteins PXO_00049 and PXO_02374 in c-di-GMP binding, regulation of virulence and motility, and subcellular localization were characterized in comparison with PXO_02715, identified previously as an interactor with the c-di-GMP receptor Filp to regulate virulence. The c-di-GMP binding motifs in the PilZ domains were conserved in PXO_00049 and PXO_02374 but were less well conserved in PXO_02715. PXO_00049 and PXO_02374 but not PXO_02715 proteins bound to c-di-GMP with high affinityin vitro, and the R141and R10residues in the PilZ domains of PXO_00049 and PXO_02374, respectively, were crucial for c-di-GMP binding. Gene deletion of PXO_00049 and PXO_02374 resulted in significant increases in virulence andhrpgene transcription, indicating their negative regulation of virulence via type III secretion system expression. All mutants showed significant changes in sliding motility but not exopolysaccharide production and biofilm formation. Intransexpression of the full-length open reading frame (ORF) of each gene in the relevant mutants led to restoration of the phenotype to wild-type levels. Moreover, PXO_00049 and PXO_02374 displayed mainly multisite subcellular localizations, whereas PXO_02715 showed nonpolar distributions in theX. oryzaepv. oryzae cells. Therefore, this study demonstrated the different functions of the PilZ domain proteins in mediation of c-di-GMP regulation of virulence and motility inX. oryzaepv. oryzae.

scholarly journals The ABC-Type Efflux Pump MacAB Protects Salmonella enterica serovar Typhimurium from Oxidative Stress

mBio ◽  
2013 ◽  
Vol 4 (6) ◽  
Author(s):  
Lydia M. Bogomolnaya ◽  
Katharine D. Andrews ◽  
Marissa Talamantes ◽  
Aimee Maple ◽  
Yury Ragoza ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Salmonella Enterica ◽  
Efflux Pump ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Drug Efflux Pump

ABSTRACTMultidrug efflux pumps are integral membrane proteins known to actively excrete antibiotics. The macrolide-specific pump MacAB, the only ABC-type drug efflux pump inSalmonella, has previously been linked to virulence in mice. The molecular mechanism of this link betweenmacABand infection is unclear. We demonstrate thatmacABplays a role in the detoxification of reactive oxygen species (ROS), compounds that salmonellae are exposed to at various stages of infection.macABis induced upon exposure to H2O2and is critical for survival ofSalmonella entericaserovar Typhimurium in the presence of peroxide. Furthermore, we determined thatmacABis required for intracellular replication inside J774.A1 murine macrophages but is not required for survival in ROS-deficient J774.D9 macrophages.macABmutants also had reduced survival in the intestine in the mouse colitis model, a model characterized by a strong neutrophilic intestinal infiltrate where bacteria may experience the cytotoxic actions of ROS. Using an Amplex red-coupled assay,macABmutants appear to be unable to induce protection against exogenous H2O2in vitro, in contrast to the isogenic wild type. In mixed cultures, the presence of the wild-type organism, or media preconditioned by the growth of the wild-type organism, was sufficient to rescue themacABmutant from peroxide-mediated killing. Our data indicate that the MacAB drug efflux pump has functions beyond resistance to antibiotics and plays a role in the protection ofSalmonellaagainst oxidative stress. Intriguingly, our data also suggest the presence of a soluble anti-H2O2compound secreted bySalmonellacells through a MacAB-dependent mechanism.IMPORTANCEThe ABC-type multidrug efflux pump MacAB is known to be required forSalmonella entericaserovar Typhimurium virulence after oral infection in mice, yet the function of this pump during infection is unknown. We show that this pump is necessary for colonization of niches in infected mice where salmonellae encounter oxidative stress during infection. MacAB is required for growth in cultured macrophages that produce reactive oxygen species (ROS) but is not needed in macrophages that do not generate ROS. In addition, we show that MacAB is required to resist peroxide-mediated killingin vitroand for the inactivation of peroxide in the media. Finally, wild-type organisms, or supernatant from wild-type organisms grown in the presence of peroxide, rescue the growth defect ofmacABmutants in H2O2. MacAB appears to participate in the excretion of a compound that induces protection against ROS-mediated killing, revealing a new role for this multidrug efflux pump.

scholarly journals Flagellar Localization of a Helicobacter pylori Autotransporter Protein

mBio ◽  
2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Jana N. Radin ◽  
Jennifer A. Gaddy ◽  
Christian González-Rivera ◽  
John T. Loh ◽  
Holly M. Scott Algood ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Bacterial Infections ◽  
Secreted Proteins ◽  
Wild Type ◽  
Gram Negative ◽  
Content Type ◽  
Ulcer Disease ◽  
H Pylori ◽  
Type V

ABSTRACTHelicobacter pyloricontains four genes that are predicted to encode proteins secreted by the autotransporter (type V) pathway. One of these, the pore-forming toxin VacA, has been studied in great detail, but thus far there has been very little investigation of three VacA-like proteins. We show here that all three VacA-like proteins are >250 kDa in mass and localized on the surface ofH. pylori. The expression of the threevacA-like genes is upregulated duringH. pyloricolonization of the mouse stomach compared toH. pylorigrowthin vitro, and a wild-typeH. pyloristrain outcompeted each of the three corresponding isogenic mutant strains in its ability to colonize the mouse stomach. One of the VacA-like proteins localizes to a sheath that overlies the flagellar filament and bulb, and therefore, we designate it FaaA (flagella-associated autotransporter A). In comparison to a wild-typeH. pyloristrain, an isogenicfaaAmutant strain exhibits decreased motility, decreased flagellar stability, and an increased proportion of flagella in a nonpolar site. The flagellar localization of FaaA differs markedly from the localization of other known autotransporters, and the current results reveal an important role of FaaA in flagellar localization and motility.IMPORTANCEThe pathogenesis of most bacterial infections is dependent on the actions of secreted proteins, and proteins secreted by the autotransporter pathway constitute the largest family of secreted proteins in pathogenic Gram-negative bacteria. In this study, we analyzed three autotransporter proteins (VacA-like proteins) produced byHelicobacter pylori, a Gram-negative bacterium that colonizes the human stomach and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We demonstrate that these three proteins each enhance the capacity ofH. pylorito colonize the stomach. Unexpectedly, one of these proteins (FaaA) is localized to a sheath that overliesH. pyloriflagella. The absence of FaaA results in decreasedH. pylorimotility as well as a reduction in flagellar stability and a change in flagellar localization. The atypical localization of FaaA reflects a specialized function of this autotransporter designed to optimizeH. pyloricolonization of the gastric niche.

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