Dataset Information

Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae.

ABSTRACT: The production of bacteriocins can be favorable for colonization of the host by eliminating other bacterial species that share the same environment. In Streptococcus pneumoniae, the pnc (blp) locus encoding putative bacteriocins, immunity, and export proteins is controlled by a two-component system similar to the comCDE system required for the induction of genetic competence. A detailed comparison of the pnc clusters of four genetically distinct isolates confirmed the great plasticity of this locus and documented several repeat sequences. Members of the multiple-antibiotic-resistant Spain23F-1 clone, one member of the Spain9V-3 clone, sensitive 23F strain 2306, and the TIGR4 strain produced bactericidal substances active against other gram-positive bacteria and in some cases against S. pneumoniae as well. However, other strains did not show activity against the indicator strains despite the presence of a bacteriocin cluster, indicating that other factors are required for bacteriocin activity. Analysis of strain 2306 and mutant derivatives of this strain confirmed that bacteriocin production was dependent on the two-component regulatory system and genes involved in bacteriocin transport and processing. At least one other bacteriocin gene, pncE, is located elsewhere on the chromosome and might contribute to the bacteriocin activity of this strain.

SUBMITTER: Lux T

PROVIDER: S-EPMC2168751 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae.

Lux Thomas T Nuhn Michael M Hakenbeck Regine R Reichmann Peter P

Journal of bacteriology 20070817 21

The production of bacteriocins can be favorable for colonization of the host by eliminating other bacterial species that share the same environment. In Streptococcus pneumoniae, the pnc (blp) locus encoding putative bacteriocins, immunity, and export proteins is controlled by a two-component system similar to the comCDE system required for the induction of genetic competence. A detailed comparison of the pnc clusters of four genetically distinct isolates confirmed the great plasticity of this lo ...[more]

PMID: 17704229

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Project description:Pneumococcal bacteriocins (pneumocins) are antibacterial toxins that mediate intra-species competition within the human host. However, the triggers of pneumocin expression are poorly understood. Using RNA-sequencing, we mapped the regulon of the pneumocin cluster (blp) of Streptococcus pneumoniae D39. Furthermore, by analogy with pneumococcal competence, we show that several antibiotics activate the blp-genes. Using real-time gene expression measurements we show that while the promoter driving expression of the two-component regulatory system blpR/H is constitutive, the remaining blp-promoters that control pneumocin expression, immunity and the inducer peptide BlpC, are pH-dependent and induced in the late exponential phase. Intriguingly, competence for genetic transformation, mediated by the paralogous ComD/E two-component quorum system, is induced by the same environmental cues. To test for interplay between these regulatory systems, we quantified the regulatory response to the addition of synthetic BlpC and competence-stimulating peptide (CSP). Supporting the idea of such interplay, we found that immediately upon addition of CSP, the blp-promoters were activated in a comD/E-dependent manner. After a delay, blp-expression was highly induced and was strictly dependent on blpRH and blpC. This raised the question of the mechanism of BlpC export, since bioinformatic analysis showed that the genes encoding the putative exporter for BlpC, blpAB, are not intact in strain D39 and most other strains. By contrast, all sequenced pneumococcal strains contain intact comAB genes, encoding the transport system for CSP. Consistent with the idea that comAB mediate BlpC export, we finally show that high-level expression of the blp-genes requires comAB. Together, our results demonstrate that regulation of pneumocin expression is intertwined with competence, explaining why certain antibiotics induce blp-expression. Antibiotic-induced pneumocin expression might therefore have unpredictable consequences on pneumococcal colonization dynamics by activating genes that mediate intra-specific interference competition.

Project description:Streptococcus pneumoniae is an important cause of otitis media and invasive disease. Since introduction of the heptavalent pneumococcal conjugate vaccine, there has been an increase in replacement disease due to serotype 19A clonal complex (CC)199 isolates. The goals of this study were to 1) describe genetic diversity among nineteen CC199 isolates from carriage, middle ear, blood, and cerebrospinal fluid, 2) compare CC199 19A (n = 3) and 15B/C (n = 2) isolates in the chinchilla model for pneumococcal disease, and 3) identify accessory genes associated with tissue-specific disease among a larger collection of S. pneumoniae isolates. CC199 isolates were analyzed by comparative genome hybridization. One hundred and twenty-seven genes were variably present. The CC199 phylogeny split into two main clades, one comprised predominantly of carriage isolates and another of disease isolates. Ability to colonize and cause disease did not differ by serotype in the chinchilla model. However, isolates from the disease clade were associated with faster time to bacteremia compared to carriage clade isolates. One 19A isolate exhibited hypervirulence. Twelve tissue-specific genes/regions were identified by correspondence analysis. After screening a diverse collection of 326 isolates, spr0282 was associated with carriage. Four genes/regions, SP0163, SP0463, SPN05002 and RD8a were associated with middle ear isolates. SPN05002 also associated with blood and CSF, while RD8a associated with blood isolates. The hypervirulent isolate's genome was sequenced using the Solexa paired-end sequencing platform and compared to that of a reference serotype 19A isolate, revealing the presence of a novel 20 kb region with sequence similarity to bacteriophage genes. Genetic factors other than serotype may modulate virulence potential in CC199. These studies have implications for the long-term effectiveness of conjugate vaccines. Ideally, future vaccines would target common proteins to effectively reduce carriage and disease in the vaccinated population.

Project description:The short generation time of many bacterial pathogens allows the accumulation of de novo mutations during routine culture procedures used for the preparation and propagation of bacterial stocks. Taking the major human pathogen Streptococcus pneumoniae as an example, we sought to determine the influence of standard laboratory handling of microbes on within-strain genetic diversity and explore how these changes influence virulence characteristics and experimental outcomes. A single culture of S. pneumoniae D39 grown overnight resulted in the enrichment of previously rare genotypes present in bacterial freezer stocks and the introduction of new variation to the bacterial population through the acquisition of mutations. A comparison of D39 stocks from different laboratories demonstrated how changes in bacterial population structure taking place during individual culture events can cumulatively lead to fixed, divergent change that profoundly alters virulence characteristics. The passage of D39 through mouse models of infection, a process used to standardize virulence, resulted in the enrichment of high-fitness genotypes that were originally rare (<2% frequency) in D39 culture collection stocks and the loss of previously dominant genotypes. In the most striking example, the selection of a <2%-frequency genotype carrying a mutation in sdhB, a gene thought to be essential for the establishment of lung infection, was associated with enhanced systemic virulence. Three separately passaged D39 cultures originating from the same frozen stocks showed considerable genetic divergence despite comparable virulence. IMPORTANCE Laboratory bacteriology involves the use of high-density cultures that we often assume to be clonal but that in reality are populations consisting of multiple genotypes at various abundances. We have demonstrated that the genetic structure of a single population of a widely used Streptococcus pneumoniae strain can be substantially altered by even short-term laboratory handling and culture and that, over time, this can lead to changes in virulence characteristics. Our findings suggest that caution should be applied when comparing data generated in different laboratories using the same strain but also when comparing data within laboratories over time. Given the dramatic reductions in the cost of next-generation sequencing technology in recent years, we advocate for the frequent sampling and sequencing of bacterial isolate collections.

Dataset Information

Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae.

Publications

Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae.

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