Identification of a bacteriocin and its cognate immunity factor expressed by Moraxella catarrhalis

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
BMC Microbiology (Impact Factor: 2.73). 09/2009; 9(1). DOI: 10.1186/1471-2180-9-207
Source: PubMed Central


Bacteriocins are antimicrobial proteins and peptides ribosomally synthesized by some bacteria which can effect both intraspecies and interspecies killing.

Moraxella catarrhalis strain E22 containing plasmid pLQ510 was shown to inhibit the growth of M. catarrhalis strain O35E. Two genes (mcbA and mcbB) in pLQ510 encoded proteins predicted to be involved in the secretion of a bacteriocin. Immediately downstream from these two genes, a very short ORF (mcbC) encoded a protein which had some homology to double-glycine bacteriocins produced by other bacteria. A second very short ORF (mcbI) immediately downstream from mcbC encoded a protein which had no significant similarity to other proteins in the databases. Cloning and expression of the mcbI gene in M. catarrhalis O35E indicated that this gene encoded the cognate immunity factor. Reverse transcriptase-PCR was used to show that the mcbA, mcbB, mcbC, and mcbI ORFs were transcriptionally linked. This four-gene cluster was subsequently shown to be present in the chromosome of several M. catarrhalis strains including O12E. Inactivation of the mcbA, mcbB, or mcbC ORFs in M. catarrhalis O12E eliminated the ability of this strain to inhibit the growth of M. catarrhalis O35E. In co-culture experiments involving a M. catarrhalis strain containing the mcbABCI locus and one which lacked this locus, the former strain became the predominant member of the culture after overnight growth in broth.

This is the first description of a bacteriocin and its cognate immunity factor produced by M. catarrhalis. The killing activity of the McbC protein raises the possibility that it might serve to lyse other M. catarrhalis strains that lack the mcbABCI locus, thereby making their DNA available for lateral gene transfer.

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    • "A study by Upton et al. (2001) described intra- and interspecies signaling between Streptococcus salivarius and S. pyogenes, mediated by SalA [46]. A single bacteriocin (McbC) has been described in M. catarrhalis, though the effect of this bacteriocin on GAS growth and virulence is not yet known [47]. "
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    ABSTRACT: Streptococcus pyogenes (group A Streptococcus, GAS) and Moraxella catarrhalis are important colonizers and (opportunistic) pathogens of the human respiratory tract. However, current knowledge regarding colonization and pathogenic potential of these two pathogens is based on work involving single bacterial species, even though the interplay between respiratory bacterial species is increasingly important in niche occupation and the development of disease. Therefore, to further define and understand polymicrobial species interactions, we investigated whether gene expression (and hence virulence potential) of GAS would be affected upon co-culture with M. catarrhalis. For co-culture experiments, GAS and M. catarrhalis were cultured in Todd-Hewitt broth supplemented with 0.2% yeast extract (THY) at 37°C with 5% CO2 aeration. Each strain was grown in triplicate so that triplicate experiments could be performed. Bacterial RNA was isolated, cDNA synthesized, and microarray transcriptome expression analysis performed. We observed significantly increased (≥4-fold) expression for genes playing a role in GAS virulence such as hyaluronan synthase (hasA), streptococcal mitogenic exotoxin Z (smeZ) and IgG endopeptidase (ideS). In contrast, significantly decreased (≥4-fold) expression was observed in genes involved in energy metabolism and in 12 conserved GAS two-component regulatory systems. This study provides the first evidence that M. catarrhalis increases GAS virulence gene expression during co-culture, and again shows the importance of polymicrobial infections in directing bacterial virulence.
    PLoS ONE 04/2013; 8(4):e62549. DOI:10.1371/journal.pone.0062549 · 3.23 Impact Factor
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    • "Interestingly, the BC7 plasmid-associated contig sequence possesses homologs of the bacteriocin/immunity factor complex first described in the M. catarrhalis plasmid, pLQ510 [24,26]; however, annotation records for this region also identify an incomplete VirB-family type four secretion system (T4SS), multiple transposases and a resolvase not reported in pLQ510, suggesting that this sequence may represent either an extra-chromosomally maintained conjugative plasmid or an integrative and conjugative element (ICE; recently reviewed in [27]). Phage-associated annotations varied between strains, but comprised only 0.2% to 2.5% of all identified ORFs per genome, while transposon-associated annotations accounted for only 0.15% to 0.44% of all ORFs per genome. "
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    ABSTRACT: 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. 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. 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.
    BMC Genomics 01/2011; 12(1):70. DOI:10.1186/1471-2164-12-70 · 3.99 Impact Factor
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    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).
    07/2011; 1(2):155 - 158. DOI:10.4161/mge.1.2.17632
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