Identification of a Secreted Cholesterol-Dependent Cytolysin (Mitilysin) from
            <i>Streptococcus mitis</i>

Jefferies, Johanna M.C.; Nieminen, Leena; Kirkham, Lea‐Ann S.; Johnston, Calum; Smith, A. Gordon; Mitchell, Tim

doi:10.1128/jb.01092-06

Cited by 31 publications

(41 citation statements)

References 30 publications

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“…Previous work characterized a Ply homologue termed mitilysin (Mly) in a subset of S. mitis isolates, with the protein sequences of 7 alleles reported (20). We report the characterization of a further related toxin in S. pseudopneumoniae isolates, referred to as pseudopneumolysin (pPly).…”

Section: Resultsmentioning

confidence: 99%

“…Translation of these sequences resulted in only 7 amino acid changes, with many synonymous mutations present, and 3 unique pPly alleles. Of the 7 amino acid changes, 2 were shared by both Ply and Mly (N14D and K224R), while another (20), and pPly, was explored using MEGA4 software to construct a minimum evolution tree to show the relationships between the toxin genes at the DNA level (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

“…Minimum evolution tree of ply DNA alleles and homologues in related streptococcal species. ply and mly alleles were previously described (20,21). The tree was drawn using MEGA4 software and demonstrates the relatedness of these toxins at the DNA level.…”

Section: Discussionmentioning

confidence: 99%

“…The results of the comparative genomic hybridization analysis allowed selection of homologues of pneumococcal vaccine candidates for further study in order to assess the diversity present in and genetic relationships between these genes. Recently, we identified and characterized a Ply homologue, termed mitilysin (20), in a subset of S. mitis isolates. Our results identify and further characterize a Ply homologue in S. pseudopneumoniae which is more closely related to mly than to ply.…”

Section: Figmentioning

confidence: 99%

“…Indeed, an increase in penicillin resistance in the pneumococcal population has been attributed to acquisition of resistant penicillin-binding protein variants from S. mitis and S. oralis, resulting in a "pool" of penicillin resistance genes being transferred between these species (9,12,38,41). Furthermore, homologous recombination with related VGS species has been observed in the pneumococcal virulence genes encoding IgA protease and neuraminidase A (nanA) (25,37), and homologues of pneumococcal virulence factors such as pneumolysin (Ply) and autolysin A (LytA) have been identified in related VGS species (20,32,48).…”

mentioning

confidence: 99%

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Detection of Large Numbers of Pneumococcal Virulence Genes in Streptococci of the Mitis Group

Johnston

Hinds

Smith³

et al. 2010

J Clin Microbiol

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Seven streptococcal isolates from the mitis group were analyzed for the presence of pneumococcal gene homologues by comparative genomic hybridization studies with microarrays based on open reading frames from the genomes of Streptococcus pneumoniae TIGR4 and R6. The diversity of pneumolysin (ply) and neuraminidase A (nanA) gene sequences was explored in more detail in a collection of 14 S. pseudopneumoniae and 29 mitis group isolates, respectively. The mitis group isolates used in the microarray experiments included a type strain (NCTC 12261), two S. mitis isolates from the nasopharynxes of children, one S. mitis isolate from a case of infective endocarditis, one S. mitis isolate from a dental abscess, and one S. oralis isolate and one S. pseudopneumoniae isolate from the nasopharynxes of children. The results of the microarray study showed that the 5 S. mitis isolates had homologues to between 67 and 82% of pneumococcal virulence genes, S. oralis hybridized to 83% of pneumococcal virulence genes, and S. pseudopneumoniae hybridized to 92% of identified pneumococcal virulence genes. Comparison of the pneumolysin, mitilysin (mly), and newly identified pseudopneumolysin (pply) gene sequences revealed that mly and pply genes are more closely related to each other than either is to ply. In contrast, the nanA gene sequences in the pneumococcus and streptococci from the mitis group are closely clustered together, sharing 99.4 to 99.7% sequence identity with pneumococcal nanA alleles.Streptococcus pneumoniae, also known as the pneumococcus, is an important human pathogen causing high levels of mortality worldwide. Diseases caused include meningitis, pneumonia, and otitis media. S. pneumoniae is a member of the viridans group streptococci (VGS) and is closely related to Streptococcus mitis and Streptococcus oralis, sharing Ͼ99% homology by 16S rRNA gene analysis (13,23). Recently, a subset of "atypical" pneumococci were identified that were distinct from both S. mitis and S. pneumoniae by housekeeping gene analysis (48). It is likely that these isolates belonged to the species Streptococcus pseudopneumoniae, which has since been identified, with isolates appearing phenotypically similar to S. mitis but undistinguishable from S. pneumoniae in genotypic tests (2). As a result of the close relationships between these species, clear identification can be problematic. A recent study showed that definitive species identification can be achieved by phylogenetic analysis of 4 housekeeping genes. Furthermore, although it has been reported that comparison of superoxide dismutase genes (sodA) was sufficient to identify most species, this did not distinguish between S. pneumoniae and S. pseudopneumoniae isolates (19).Despite the close genetic relationships between these species, while S. pneumoniae can be a severe pathogen, S. oralis and S. mitis are usually commensal organisms of mucous membranes. However, on rare occasions, they are able to cause opportunistic disease in immunocompromised patients, particularly those with replacem...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Detection of Large Numbers of Pneumococcal Virulence Genes in Streptococci of the Mitis Group

Johnston

Hinds

Smith³

et al. 2010

J Clin Microbiol

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The Cholesterol-Dependent Cytolysin Family of Gram-Positive Bacterial Toxins

Heuck¹,

Moe²,

Johnson³

2010

Subcellular Biochemistry

103

118

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The cholesterol-dependent cytolysins (CDCs) are a family of beta-barrel pore-forming toxins secreted by Gram-positive bacteria. These toxins are produced as water-soluble monomeric proteins that after binding to the target cell oligomerize on the membrane surface forming a ring-like pre-pore complex, and finally insert a large beta-barrel into the membrane (about 250 A in diameter). Formation of such a large transmembrane structure requires multiple and coordinated conformational changes. The presence of cholesterol in the target membrane is absolutely required for pore-formation, and therefore it was long thought that cholesterol was the cellular receptor for these toxins. However, not all the CDCs require cholesterol for binding. Intermedilysin, secreted by Streptoccocus intermedius only binds to membranes containing a protein receptor, but forms pores only if the membrane contains sufficient cholesterol. In contrast, perfringolysin O, secreted by Clostridium perfringens, only binds to membranes containing substantial amounts of cholesterol. The mechanisms by which cholesterol regulates the cytolytic activity of the CDCs are not understood at the molecular level. The C-terminus of perfringolysin O is involved in cholesterol recognition, and changes in the conformation of the loops located at the distal tip of this domain affect the toxin-membrane interactions. At the same time, the distribution of cholesterol in the membrane can modulate toxin binding. Recent studies support the concept that there is a dynamic interplay between the cholesterol-binding domain of the CDCs and the excess of cholesterol molecules in the target membrane.

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Development of amperometric magnetogenosensors coupled to asymmetric PCR for the specific detection of Streptococcus pneumoniae

et al. 2011

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A disposable magnetogenosensor for the rapid, specific and sensitive detection of Streptococcus pneumoniae is reported. The developed procedure involves the use of streptavidin-modified magnetic beads, a specific biotinylated capture probe that hybridizes with a specific region of lytA, the gene encoding the pneumococcal major autolysin, and appropriate primers for asymmetric polymerase chain reaction (PCR) amplification. Capture probes and amplicons specific for S. pneumoniae were selected by a careful analysis of all lytA alleles available. The selected primers amplify a 235-bp fragment of pneumococcal lytA. A detection limit (LOD) of 5.1 nM was obtained for a 20-mer synthetic target DNA without any amplification protocol, while the LOD for the asymmetric PCR amplicon was 1.1 nM. A RSD value of 6.9% was obtained for measurements carried out with seven different genosensors for 1.1-nM aPCR product. The strict specificity of the designed primers was demonstrated by aPCR amplification of genomic DNA prepared from different bacteria, including some closely related streptococci. Direct asymmetric PCR (daPCR), using cells directly from broth cultures of S. pneumoniae, showed that daPCR products could be prepared with as few as 2 colony-forming units (CFU). Furthermore, this methodology did not show any cross-reaction with closely related streptococci such as Streptococcus mitis (or Streptococcus pseudopneumoniae) even when present in the culture at concentrations up to 10(5) times higher than that of S. pneumoniae. Preliminary data for rapid detection of pneumococcus directly in clinical samples has shown that it is possible to discriminate between non-inoculated blood and urine samples and samples inoculated with only 10(3) CFU mL(-1) S. pneumoniae.

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Identification of a Secreted Cholesterol-Dependent Cytolysin (Mitilysin) from Streptococcus mitis

Cited by 31 publications

References 30 publications

Detection of Large Numbers of Pneumococcal Virulence Genes in Streptococci of the Mitis Group

Detection of Large Numbers of Pneumococcal Virulence Genes in Streptococci of the Mitis Group

The Cholesterol-Dependent Cytolysin Family of Gram-Positive Bacterial Toxins

Development of amperometric magnetogenosensors coupled to asymmetric PCR for the specific detection of Streptococcus pneumoniae

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