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Evans AS, Pybus C, Hansen EJ. Development of a LacZ-based transcriptional reporter system for use with Moraxella catarrhalis. Plasmid 2012; 69:180-5. [PMID: 23219721 DOI: 10.1016/j.plasmid.2012.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 11/20/2012] [Indexed: 01/13/2023]
Abstract
The lack of a transcriptional reporter system for use in Moraxella catarrhalis has hindered studies of gene regulation in this pathogen. PCR and recombinant DNA methods were used to insert a multicloning site (MCS) and promoterless full-length Escherichia coli lacZ gene, flanked by transcriptional terminators both immediately upstream and downstream, into the M. catarrhalis recombinant plasmid pWW115. Insertion into the MCS in the newly constructed plasmid pASE222 of M. catarrhalis promoter regions controlled by either a repressor (i.e., NsrR) or activator (i.e., PhoB) yielded transcriptional fusion constructs that were appropriately responsive to signal inputs dependent on the host strain genotype, as measured quantitatively by means of a Miller β-galactosidase assay. The transcriptional reporter plasmid pASE222 should prove to be a useful tool for rapid screening of factors affecting gene expression in M. catarrhalis.
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Affiliation(s)
- Amanda S Evans
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
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52
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de Vries SPW, Burghout P, Langereis JD, Zomer A, Hermans PWM, Bootsma HJ. Genetic requirements for Moraxella catarrhalis growth under iron-limiting conditions. Mol Microbiol 2012; 87:14-29. [PMID: 23163337 DOI: 10.1111/mmi.12081] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2012] [Indexed: 11/26/2022]
Abstract
Iron sequestration by the human host is a first line defence against respiratory pathogens like Moraxella catarrhalis, which consequently experiences a period of iron starvation during colonization. We determined the genetic requirements for M. catarrhalis BBH18 growth during iron starvation using the high-throughput genome-wide screening technology genomic array footprinting (GAF). By subjecting a large random transposon mutant library to growth under iron-limiting conditions, mutants of the MCR_0996-rhlB-yggW operon, rnd, and MCR_0457 were negatively selected. Growth experiments using directed mutants confirmed the GAF phenotypes with ΔyggW (putative haem-shuttling protein) and ΔMCR_0457 (hypothetical protein) most severely attenuated during iron starvation, phenotypes which were restored upon genetic complementation of the deleted genes. Deletion of yggW resulted in similar attenuated phenotypes in three additional strains. Transcriptional profiles of ΔyggW and ΔMCR_0457 were highly altered with 393 and 192 differentially expressed genes respectively. In all five mutants, expression of nitrate reductase genes was increased and of nitrite reductase decreased, suggesting an impaired aerobic respiration. Alteration of iron metabolism may affect nasopharyngeal colonization as adherence of all mutants to respiratory tract epithelial cells was attenuated. In conclusion, we elucidated the genetic requirements for M. catarrhalis growth during iron starvation and characterized the roles of the identified genes in bacterial growth and host interaction.
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Affiliation(s)
- Stefan P W de Vries
- Laboratory of Pediatric Infectious Diseases, Radboud University Medical Centre, Nijmegen, the Netherlands
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53
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Saito R, Nonaka S, Nishiyama H, Okamura N. Molecular mechanism of macrolide–lincosamide resistance in Moraxella catarrhalis. J Med Microbiol 2012; 61:1435-1438. [DOI: 10.1099/jmm.0.046706-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Ryoichi Saito
- Department of Microbiology and Immunology, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Shotaro Nonaka
- Department of Microbiology and Immunology, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Hiroyuki Nishiyama
- Clinical Laboratory Department, Surugadai Nihon University Hospital, 1-8-13 Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8309, Japan
- Department of Microbiology and Immunology, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Noboru Okamura
- Department of Microbiology and Immunology, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
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A novel group of Moraxella catarrhalis UspA proteins mediates cellular adhesion via CEACAMs and vitronectin. PLoS One 2012; 7:e45452. [PMID: 23049802 PMCID: PMC3458076 DOI: 10.1371/journal.pone.0045452] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 08/22/2012] [Indexed: 02/01/2023] Open
Abstract
Moraxella catarrhalis (Mx) is a common cause of otitis media and exacerbation of chronic obstructive pulmonary disease, an increasing worldwide problem. Surface proteins UspA1 and UspA2 of Mx bind to a number of human receptors and may function in pathogenesis. Genetic recombination events in the pathogen can generate hybrid proteins termed UspA2H. However, whether certain key functions (e.g. UspA1-specific CEACAM binding) can be exchanged between these adhesin families remains unknown. In this study, we have shown that Mx can incorporate the UspA1 CEACAM1-binding region not only into rare UspA1 proteins devoid of CEACAM-binding ability, but also into UspA2 which normally lack this capacity. Further, a screen of Mx isolates revealed the presence of novel UspA2 Variant proteins (UspA2V) in ∼14% of the CEACAM-binding population. We demonstrate that the expression of UspA2/2V with the CEACAM-binding domain enable Mx to bind both to cell surface CEACAMs and to integrins, the latter via vitronectin. Such properties of UspA2/2V have not been reported to date. The studies demonstrate that the UspA family is much more heterogeneous than previously believed and illustrate the in vivo potential for exchange of functional regions between UspA proteins which could convey novel adhesive functions whilst enhancing immune evasion.
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55
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Pneumococcal carbohydrate transport: food for thought. Trends Microbiol 2012; 20:517-22. [PMID: 22959614 DOI: 10.1016/j.tim.2012.08.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 08/10/2012] [Accepted: 08/16/2012] [Indexed: 02/05/2023]
Abstract
Streptococcus pneumoniae relies exclusively on carbohydrates as a carbon source and devotes 30% of all transport mechanisms to carbohydrate import. Pneumococci utilize at least 32 carbohydrates in vitro. However, some proposed substrates are not human-derived, so it is unclear where they are encountered in the host niche, and other substrates remain unidentified. The majority of transporter loci are conserved, arguing against redundancy and instead for distinct roles during pathogenesis. Despite this, expression and regulation of carbohydrate transporters in vivo remain ill defined. Recent work has also demonstrated that multiple ABC transporters share an ATPase; whether this evolved for genome minimization or for transporter regulation remains unknown. Continued efforts to understand carbohydrate import may reveal novel vaccine and therapeutic targets and increase our understanding of pneumococcal pathogenesis.
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56
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Akochy PM, Lapointe J, Roy PH. Natural insertion of the bro-1 β-lactamase gene into the gatCAB operon affects Moraxella catarrhalis aspartyl-tRNAAsn amidotransferase activity. Microbiology (Reading) 2012; 158:2363-2371. [DOI: 10.1099/mic.0.060095-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- Pierre-Marie Akochy
- Centre de Recherche en Infectiologie, CHUQ Pavillon CHUL, 2705 boul. Laurier, RC-709, QC G1V 4G2, Canada
- Institut Pasteur de Côte d’Ivoire, 01 BP 490 Abidjan, Côte d’Ivoire
- Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, QC G1V 0A6, Canada
| | - Jacques Lapointe
- Institut de biologie intégrative et des systèmes (IBIS), Pavillon Charles-Eugène-Marchand, G1V 0A6, Canada
- Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, QC G1V 0A6, Canada
| | - Paul H. Roy
- Centre de Recherche en Infectiologie, CHUQ Pavillon CHUL, 2705 boul. Laurier, RC-709, QC G1V 4G2, Canada
- Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, QC G1V 0A6, Canada
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Mao X, Zhang H, Yin Y, Xu Y. The percentage of bacterial genes on leading versus lagging strands is influenced by multiple balancing forces. Nucleic Acids Res 2012; 40:8210-8. [PMID: 22735706 PMCID: PMC3458553 DOI: 10.1093/nar/gks605] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The majority of bacterial genes are located on the leading strand, and the percentage of such genes has a large variation across different bacteria. Although some explanations have been proposed, these are at most partial explanations as they cover only small percentages of the genes and do not even consider the ones biased toward the lagging strand. We have carried out a computational study on 725 bacterial genomes, aiming to elucidate other factors that may have influenced the strand location of genes in a bacterium. Our analyses suggest that (i) genes of some functional categories such as ribosome have higher preferences to be on the leading strands; (ii) genes of some functional categories such as transcription factor have higher preferences on the lagging strands; (iii) there is a balancing force that tends to keep genes from all moving to the leading and more efficient strand and (iv) the percentage of leading-strand genes in an bacterium can be accurately explained based on the numbers of genes in the functional categories outlined in (i) and (ii), genome size and gene density, indicating that these numbers implicitly contain the information about the percentage of genes on the leading versus lagging strand in a genome.
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Affiliation(s)
- Xizeng Mao
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30605, USA
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58
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Liu Y, Zhao C, Zhang F, Chen H, Chen M, Wang H. High prevalence and molecular analysis of macrolide-nonsusceptible Moraxella catarrhalis isolated from nasopharynx of healthy children in China. Microb Drug Resist 2012; 18:417-26. [PMID: 22394083 DOI: 10.1089/mdr.2011.0175] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Three hundred eighty-three isolates of Moraxella catarrhalis were collected from healthy children aged less than 2 years in China and assessed for antimicrobial resistance. We found that 92.2% (n=353) produced a β-lactamase. Nonsusceptibility rates to erythromycin and azithromycin, determined using Clinical Laboratory Standards Institute (CLSI) breakpoints, were 40.3% and 22.5%, respectively; nonsusceptibility rates determined using pharmacokinetics/pharmacodynamics breakpoints, however, were 59% and 60.1%. The minimal inhibitory concentration (MIC)(90) values were >256 μg/ml. Nonsusceptibility rates varied by region from 9.7% in Dongguan to 75.9% in Jinan. Further, concomitant resistance to β-lactam antibiotics was also observed. Pulsed-field gel electrophoresis analysis of 27/37 high-level macrolide-resistant M. catarrhalis isolates showed that closely related pulsotypes dominated, with a total of 11 different pulsotypes being observed. The closely related pulsotypes were observed in isolates originating from all six Chinese cities investigated, possibly as a consequence of the mobility of the Chinese population. Sixteen patterns of 23S rRNA mutations were found among 97 selected isolates using polymerase chain reaction and sequencing, but no known ermA, ermB, mefA, or mefE genes could be detected. Mutations A2982T and A2796T in 23S rRNA were related to high-level macrolide resistance (MICs ranging from 24 to >256 μg/ml), while an A2983T mutation was associated with low-level macrolide resistance (MICs ranging from 0.19 to 16 μg/ml).
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Affiliation(s)
- Yali Liu
- Department of Clinical Laboratory, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
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59
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Use of the chinchilla model for nasopharyngeal colonization to study gene expression by Moraxella catarrhalis. Infect Immun 2011; 80:982-95. [PMID: 22184412 DOI: 10.1128/iai.05918-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Young adult chinchillas were atraumatically inoculated with Moraxella catarrhalis via the nasal route. Detailed histopathologic examination of nasopharyngeal tissues isolated from these M. catarrhalis-infected animals revealed the presence of significant inflammation within the epithelium. Absence of similar histopathologic findings in sham-inoculated animals confirmed that M. catarrhalis was exposed to significant host-derived factors in this environment. Twenty-four hours after inoculation, viable M. catarrhalis organisms were recovered from the nasal cavity and nasopharynx of the animals in numbers sufficient for DNA microarray analysis. More than 100 M. catarrhalis genes were upregulated in vivo, including open reading frames (ORFs) encoding proteins that are involved in a truncated denitrification pathway or in the oxidative stress response, as well as several putative transcriptional regulators. Additionally, 200 M. catarrhalis genes were found to be downregulated when this bacterium was introduced into the nasopharynx. These downregulated genes included ORFs encoding several well-characterized M. catarrhalis surface proteins including Hag, McaP, and MchA1. Real-time reverse transcriptase PCR (RT-PCR) was utilized as a stringent control to validate the results of in vivo gene expression patterns as measured by DNA microarray analysis. Inactivation of one of the genes (MC ORF 1550) that was upregulated in vivo resulted in a decrease in the ability of M. catarrhalis to survive in the chinchilla nasopharynx over a 3-day period. This is the first evaluation of global transcriptome expression by M. catarrhalis cells in vivo.
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60
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Hays J. Mobile genetic elements in Moraxella catarrhalis. Mob Genet Elements 2011; 1:155-158. [PMID: 22016866 DOI: 10.4161/mge.1.2.17632] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 08/04/2011] [Accepted: 08/04/2011] [Indexed: 12/26/2022] Open
Abstract
Moraxella catarrhalis is a Gram-negative diplococcus that is a strict human pathogen, which for a long period of time was regarded as a simple commensal. Research now shows that this organism is a pathogen its own right and is associated with both upper and lower respiratory tract infections. Further, there appears to be a dichotomy in the pathogenic potential of M. catarrhalis with upper respiratory tract infections mainly occurring in children, and lower respiratory tract infections mainly occurring in adults with predisposing pulmonary complications e.g., chronic obstructive pulmonary disease (COPD).
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Affiliation(s)
- John Hays
- Deptartment of Medical Microbiology and Infectious Disease; Erasmus MC; Rotterdam, The Netherlands
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61
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Moraxella catarrhalis outer membrane vesicles carry β-lactamase and promote survival of Streptococcus pneumoniae and Haemophilus influenzae by inactivating amoxicillin. Antimicrob Agents Chemother 2011; 55:3845-53. [PMID: 21576428 DOI: 10.1128/aac.01772-10] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Moraxella catarrhalis is a common pathogen found in children with upper respiratory tract infections and in patients with chronic obstructive pulmonary disease during exacerbations. The bacterial species is often isolated together with Streptococcus pneumoniae and Haemophilus influenzae. Outer membrane vesicles (OMVs) are released by M. catarrhalis and contain phospholipids, adhesins, and immunomodulatory compounds such as lipooligosaccharide. We have recently shown that M. catarrhalis OMVs exist in patients upon nasopharyngeal colonization. As virtually all M. catarrhalis isolates are β-lactamase positive, the goal of this study was to investigate whether M. catarrhalis OMVs carry β-lactamase and to analyze if OMV consequently can prevent amoxicillin-induced killing. Recombinant β-lactamase was produced and antibodies were raised in rabbits. Transmission electron microscopy, flow cytometry, and Western blotting verified that OMVs carried β-lactamase. Moreover, enzyme assays revealed that M. catarrhalis OMVs contained active β-lactamase. OMVs (25 μg/ml) incubated with amoxicillin for 1 h completely hydrolyzed amoxicillin at concentrations up to 2.5 μg/ml. In functional experiments, preincubation of amoxicillin (10× MIC) with M. catarrhalis OMVs fully rescued amoxicillin-susceptible M. catarrhalis, S. pneumoniae, and type b or nontypeable H. influenzae from β-lactam-induced killing. Our results suggest that the presence of amoxicillin-resistant M. catarrhalis originating from β-lactamase-containing OMVs may pave the way for respiratory pathogens that by definition are susceptible to β-lactam antibiotics.
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62
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Hallström T, Nordström T, Tan TT, Manolov T, Lambris JD, Isenman DE, Zipfel PF, Blom AM, Riesbeck K. Immune evasion of Moraxella catarrhalis involves ubiquitous surface protein A-dependent C3d binding. THE JOURNAL OF IMMUNOLOGY 2011; 186:3120-9. [PMID: 21270401 DOI: 10.4049/jimmunol.1002621] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The complement system plays an important role in eliminating invading pathogens. Activation of complement results in C3b deposition (opsonization), phagocytosis, anaphylatoxin (C3a, C5a) release, and consequently cell lysis. Moraxella catarrhalis is a human respiratory pathogen commonly found in children with otitis media and in adults with chronic obstructive pulmonary disease. The species has evolved multiple complement evasion strategies, which among others involves the ubiquitous surface protein (Usp) family consisting of UspA1, A2, and A2 hybrid. In the present study, we found that the ability of M. catarrhalis to bind C3 correlated with UspA expression and that C3 binding contributed to serum resistance in a large number of clinical isolates. Recombinantly expressed UspA1 and A2 inhibit both the alternative and classical pathways, C3b deposition, and C3a generation when bound to the C3 molecule. We also revealed that the M. catarrhalis UspA-binding domain on C3b was located to C3d and that the major bacterial C3d-binding domains were within UspA1(299-452) and UspA2(165-318). The interaction with C3 was not species specific since UspA-expressing M. catarrhalis also bound mouse C3 that resulted in inhibition of the alternative pathway of mouse complement. Taken together, the binding of C3 to UspAs is an efficient strategy of Moraxella to block the activation of complement and to inhibit C3a-mediated inflammation.
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Affiliation(s)
- Teresia Hallström
- Department of Laboratory Medicine Malmö, Lund University, Skåne University Hospital, Malmö, Sweden
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63
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Davie JJ, Earl J, de Vries SPW, Ahmed A, Hu FZ, Bootsma HJ, Stol K, Hermans PWM, Wadowsky RM, Ehrlich GD, Hays JP, Campagnari AA. Comparative analysis and supragenome modeling of twelve Moraxella catarrhalis clinical isolates. BMC Genomics 2011; 12:70. [PMID: 21269504 PMCID: PMC3045334 DOI: 10.1186/1471-2164-12-70] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 01/26/2011] [Indexed: 12/18/2022] Open
Abstract
Background M. catarrhalis is a gram-negative, gamma-proteobacterium and an opportunistic human pathogen associated with otitis media (OM) and exacerbations of chronic obstructive pulmonary disease (COPD). With direct and indirect costs for treating these conditions annually exceeding $33 billion in the United States alone, and nearly ubiquitous resistance to beta-lactam antibiotics among M. catarrhalis clinical isolates, a greater understanding of this pathogen's genome and its variability among isolates is needed. Results The genomic sequences of ten geographically and phenotypically diverse clinical isolates of M. catarrhalis were determined and analyzed together with two publicly available genomes. These twelve genomes were subjected to detailed comparative and predictive analyses aimed at characterizing the supragenome and understanding the metabolic and pathogenic potential of this species. A total of 2383 gene clusters were identified, of which 1755 are core with the remaining 628 clusters unevenly distributed among the twelve isolates. These findings are consistent with the distributed genome hypothesis (DGH), which posits that the species genome possesses a far greater number of genes than any single isolate. Multiple and pair-wise whole genome alignments highlight limited chromosomal re-arrangement. Conclusions M. catarrhalis gene content and chromosomal organization data, although supportive of the DGH, show modest overall genic diversity. These findings are in stark contrast with the reported heterogeneity of the species as a whole, as wells as to other bacterial pathogens mediating OM and COPD, providing important insight into M. catarrhalis pathogenesis that will aid in the development of novel therapeutic regimens.
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Affiliation(s)
- Jeremiah J Davie
- Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York, USA
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64
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Luke-Marshall NR, Sauberan SL, Campagnari AA. Comparative analyses of the Moraxella catarrhalis type-IV pilus structural subunit PilA. Gene 2011; 477:19-23. [PMID: 21256201 DOI: 10.1016/j.gene.2011.01.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 01/05/2011] [Accepted: 01/11/2011] [Indexed: 10/18/2022]
Abstract
Moraxella catarrhalis is a Gram-negative aerobic diplococcus that is a mucosal pathogen of the upper and lower respiratory tracts in humans. In order to colonize the human host and establish an infection, M. catarrhalis must be able to effectively attach to the respiratory mucosal epithelia. Although little is known about M. catarrhalis pathogenesis, our laboratory has previously shown that expression of type IV pili (TFP) contributes to mucosal colonization. TFP are filamentous surface appendages primarily composed of a single protein subunit termed pilin, which is encoded by pilA in M. catarrhalis. These surface structures play a crucial role in the initiation of disease by a wide range of pathogenic bacteria. Our studies also indicate that unlike the pilin of the pathogenic Neisseria species, which exhibit both phase and antigenic variation, the pilin subunit of M. catarrhalis appears to be more highly conserved as there are no major pilin variants produced by a single strain and only two major PilA antigenic variants, termed clade 1 and clade 2, have been observed between strains. Moreover, we have determined that these highly conserved bacterial surface structures are expressed by all M. catarrhalis clinical isolates evaluated. Therapeutic or vaccine-based interventions that prevent or diminish nasopharyngeal colonization will likely decrease acute and recurrent M. catarrhalis infections in prone populations. Thus, our data indicate that additional studies aimed at elucidating the role of PilA in the pathogenesis and host response to M. catarrhalis infections are warranted.
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Affiliation(s)
- Nicole R Luke-Marshall
- Department of Microbiology and Immunology, State University of New York at Buffalo, Buffalo, NY 14214, USA
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65
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Characterization and evaluation of the Moraxella catarrhalis oligopeptide permease A as a mucosal vaccine antigen. Infect Immun 2010; 79:846-57. [PMID: 21134967 DOI: 10.1128/iai.00314-10] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Moraxella catarrhalis is a common cause of otitis media in children and of lower respiratory tract infections in adults with chronic obstructive pulmonary disease; therefore, these two groups would benefit from a vaccine to prevent M. catarrhalis infections. A genome mining approach for vaccine antigens identified oligopeptide permease protein A (OppA), an oligopeptide binding protein of an apparent oligopeptide transport system. Analysis of the oppA gene by PCR and sequence analysis revealed that OppA is highly conserved among clinical isolates of M. catarrhalis. Recombinant OppA was expressed as a lipoprotein and purified, and an oppA knockout mutant was constructed. Antiserum raised to recombinant purified OppA recognized epitopes on the bacterial surface of the wild type but not the OppA knockout mutant. Antibodies raised to purified recombinant OppA recognized native OppA in multiple strains. Intranasal immunization of mice induced systemic and mucosal antibodies to OppA and resulted in enhanced clearance of M. catarrhalis in a mouse pulmonary clearance model. OppA is a highly conserved, immunogenic protein that expresses epitopes on the bacterial surface and that induces potentially protective immune responses in a mouse model. OppA should be evaluated further as a vaccine antigen for M. catarrhalis.
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Schaar V, de Vries SPW, Perez Vidakovics MLA, Bootsma HJ, Larsson L, Hermans PWM, Bjartell A, Mörgelin M, Riesbeck K. Multicomponent Moraxella catarrhalis outer membrane vesicles induce an inflammatory response and are internalized by human epithelial cells. Cell Microbiol 2010; 13:432-49. [PMID: 21044239 DOI: 10.1111/j.1462-5822.2010.01546.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Moraxella catarrhalis is an emerging human respiratory pathogen in patients with chronic obstructive pulmonary disease (COPD) and in children with acute otitis media. The specific secretion machinery known as outer membrane vesicles (OMVs) is a mechanism by which Gram-negative pathogens interact with host cells during infection. We identified 57 proteins in M. catarrhalis OMVs using a proteomics approach combining two-dimensional SDS-PAGE and MALDI-TOF mass spectrometry analysis. The OMVs contained known surface proteins such as ubiquitous surface proteins (Usp) A1/A2, and Moraxella IgD-binding protein (MID). Most of the proteins are adhesins/virulence factors triggering the immune response, but also aid bacteria to evade the host defence. FITC-stained OMVs bound to lipid raft domains in alveolar epithelial cells and were internalized after interaction with Toll-like receptor 2 (TLR2), suggesting a delivery to the host tissue of a large and complex group of OMV-attributed proteins. Interestingly, OMVs modulated the pro-inflammatory response in epithelial cells, and UspA1-bearing OMVs were found to specifically downregulate the reaction. When mice were exposed to OMVs, a pulmonary inflammation was clearly seen. Our findings indicate that Moraxella OMVs are highly biologically active, transport main bacterial virulence factors and may modulate the epithelial pro-inflammatory response.
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Affiliation(s)
- Viveka Schaar
- Medical Microbiology, Department of Laboratory Medicine Malmö, Lund University, Skåne University Hospital, Sweden
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67
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Ayers M, Howell PL, Burrows LL. Architecture of the type II secretion and type IV pilus machineries. Future Microbiol 2010; 5:1203-18. [PMID: 20722599 DOI: 10.2217/fmb.10.76] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Motility and protein secretion are key processes contributing to bacterial virulence. A wealth of phylogenetic, biochemical and structural evidence support the hypothesis that the widely distributed type IV pilus (T4P) system, involved in twitching motility, and the type II secretion (T2S) system, involved in exoprotein release, are descended from a common progenitor. Both are composed of dedicated but dynamic assemblages, which have been proposed to function through alternate polymerization and depolymerization or degradation of pilin-like subunits. While ongoing studies aimed at understanding the details of assembly and function of these systems are leading to new insights, there are still large knowledge gaps with respect to several fundamental aspects of their biology, including the localization and stoichiometry of critical assembly components, and the nature of their interactions. This article highlights recent advances in understanding the architectures of the T4P and T2S systems, and the organization of their inner and outer membrane components. As structural data accumulates, it is becoming increasingly apparent that even components with little-to-no sequence similarity have similar folds, further supporting the idea that both systems function by a similar mechanism.
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Affiliation(s)
- Melissa Ayers
- Department of Biochemistry & Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, ON, Canada
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Identification of gene products involved in the oxidative stress response of Moraxella catarrhalis. Infect Immun 2010; 79:745-55. [PMID: 21098105 DOI: 10.1128/iai.01060-10] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Moraxella catarrhalis is subjected to oxidative stress from both internal and environmental sources. A previous study (C. D. Pericone, K. Overweg, P. W. Hermans, and J. N. Weiser, Infect. Immun. 68:3990-3997, 2000) indicated that a wild-type strain of M. catarrhalis was very resistant to killing by exogenous hydrogen peroxide (H₂O₂). The gene encoding OxyR, a LysR family transcriptional regulator, was identified and inactivated in M. catarrhalis strain O35E, resulting in an increase in sensitivity to killing by H₂O₂ in disk diffusion assays and a concomitant aerobic serial dilution effect. Genes encoding a predicted catalase (KatA) and an alkyl hydroperoxidase (AhpCF) showed dose-dependent upregulation in wild-type cells exposed to H₂O₂. DNA microarray and real-time reverse transcription-PCR (RT-PCR) analyses identified M. catarrhalis genes whose expression was affected by oxidative stress in an OxyR-dependent manner. Testing of M. catarrhalis O35E katA and ahpC mutants for their abilities to scavenge exogenous H₂O₂ showed that the KatA catalase was responsible for most of this activity in the wild-type parent strain. The introduction of the same mutations into M. catarrhalis strain ETSU-4 showed that the growth of a ETSU-4 katA mutant was markedly inhibited by the addition of 50 mM H₂O₂ but that this mutant could still form a biofilm equivalent to that produced by its wild-type parent strain.
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