<named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes
ABSTRACT Streptococcus pneumoniae (pneumococcus) is a leading human pathogen that can cause serious localized and invasive diseases. Pneumococci can undergo a spontaneous and reversible phase variation that is reflected in colony opacity and which allows the population to adapt to different host env...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2017-12-01
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| Series: | mSphere |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/mSphere.00386-17 |
| _version_ | 1818398529300725760 |
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| author | Melissa B. Oliver Ankita Basu Roy Ranjit Kumar Elliot J. Lefkowitz W. Edward Swords |
| author_facet | Melissa B. Oliver Ankita Basu Roy Ranjit Kumar Elliot J. Lefkowitz W. Edward Swords |
| author_sort | Melissa B. Oliver |
| collection | DOAJ |
| description | ABSTRACT Streptococcus pneumoniae (pneumococcus) is a leading human pathogen that can cause serious localized and invasive diseases. Pneumococci can undergo a spontaneous and reversible phase variation that is reflected in colony opacity and which allows the population to adapt to different host environments. Generally, transparent variants are adapted for nasopharyngeal colonization, whereas opaque variants are associated with invasive disease. In recent work, colony phase variation was shown to occur by means of recombination events to generate multiple alleles of the hsdS targeting domain of a DNA methylase complex, which mediates epigenetic changes in gene expression. A panel of isogenic strains were created in the well-studied S. pneumoniae TIGR4 background that are “locked” in the transparent (n = 4) or opaque (n = 2) colony phenotype. The strains had significant differences in colony size which were stable over multiple passages in vitro and in vivo. While there were no significant differences in adherence for the phase-locked mutant strains to immortalized epithelial cells, biofilm formation and viability were reduced for the opaque variants in static assays. Nasopharyngeal colonization was stable for all strains, but the mortality rates differed between them. Transcript profiling by transcriptome sequencing (RNA-seq) analyses revealed that the expression levels of certain virulence factors were increased in a phase-specific manner. As epigenetic regulation of phase variation (often referred to as "phasevarion") is emerging as a common theme for mucosal pathogens, these results serve as a model for future studies of host-pathogen interactions. IMPORTANCE A growing number of bacterial species undergo epigenetic phase variation due to variable expression or specificity of DNA-modifying enzymes. For pneumococci, this phase variation has long been appreciated as being revealed by changes in colony opacity, which are reflected in changes in expression or accessibility of factors on the bacterial surface. Recent work showed that recombination-generated variation in alleles of the HsdS DNA methylase specificity subunit mediated pneumococcal phase variation. We generated phase-locked populations of S. pneumoniae TIGR4 expressing a single nonvariant hsdS allele and observed significant differences in gene expression and virulence. These results highlight the importance of focused pathogenesis studies within specific phase types. Moreover, the generation of single-allele hsdS constructs will greatly facilitate such studies. |
| first_indexed | 2024-12-14T07:06:14Z |
| format | Article |
| id | doaj.art-d7a553d2d0094ca295946d425fc9e4f5 |
| institution | Directory Open Access Journal |
| issn | 2379-5042 |
| language | English |
| last_indexed | 2024-12-14T07:06:14Z |
| publishDate | 2017-12-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mSphere |
| spelling | doaj.art-d7a553d2d0094ca295946d425fc9e4f52022-12-21T23:12:12ZengAmerican Society for MicrobiologymSphere2379-50422017-12-012610.1128/mSphere.00386-17<named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence PhenotypesMelissa B. Oliver0Ankita Basu Roy1Ranjit Kumar2Elliot J. Lefkowitz3W. Edward Swords4Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USADepartment of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USABiomedical Informatics, Center for Clinical and Translational Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USABiomedical Informatics, Center for Clinical and Translational Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USADepartment of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USAABSTRACT Streptococcus pneumoniae (pneumococcus) is a leading human pathogen that can cause serious localized and invasive diseases. Pneumococci can undergo a spontaneous and reversible phase variation that is reflected in colony opacity and which allows the population to adapt to different host environments. Generally, transparent variants are adapted for nasopharyngeal colonization, whereas opaque variants are associated with invasive disease. In recent work, colony phase variation was shown to occur by means of recombination events to generate multiple alleles of the hsdS targeting domain of a DNA methylase complex, which mediates epigenetic changes in gene expression. A panel of isogenic strains were created in the well-studied S. pneumoniae TIGR4 background that are “locked” in the transparent (n = 4) or opaque (n = 2) colony phenotype. The strains had significant differences in colony size which were stable over multiple passages in vitro and in vivo. While there were no significant differences in adherence for the phase-locked mutant strains to immortalized epithelial cells, biofilm formation and viability were reduced for the opaque variants in static assays. Nasopharyngeal colonization was stable for all strains, but the mortality rates differed between them. Transcript profiling by transcriptome sequencing (RNA-seq) analyses revealed that the expression levels of certain virulence factors were increased in a phase-specific manner. As epigenetic regulation of phase variation (often referred to as "phasevarion") is emerging as a common theme for mucosal pathogens, these results serve as a model for future studies of host-pathogen interactions. IMPORTANCE A growing number of bacterial species undergo epigenetic phase variation due to variable expression or specificity of DNA-modifying enzymes. For pneumococci, this phase variation has long been appreciated as being revealed by changes in colony opacity, which are reflected in changes in expression or accessibility of factors on the bacterial surface. Recent work showed that recombination-generated variation in alleles of the HsdS DNA methylase specificity subunit mediated pneumococcal phase variation. We generated phase-locked populations of S. pneumoniae TIGR4 expressing a single nonvariant hsdS allele and observed significant differences in gene expression and virulence. These results highlight the importance of focused pathogenesis studies within specific phase types. Moreover, the generation of single-allele hsdS constructs will greatly facilitate such studies.https://journals.asm.org/doi/10.1128/mSphere.00386-17Streptococcus pneumoniaephase variationpneumococcus |
| spellingShingle | Melissa B. Oliver Ankita Basu Roy Ranjit Kumar Elliot J. Lefkowitz W. Edward Swords <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes mSphere Streptococcus pneumoniae phase variation pneumococcus |
| title | <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes |
| title_full | <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes |
| title_fullStr | <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes |
| title_full_unstemmed | <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes |
| title_short | <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> TIGR4 Phase-Locked Opacity Variants Differ in Virulence Phenotypes |
| title_sort | named content content type genus species streptococcus pneumoniae named content tigr4 phase locked opacity variants differ in virulence phenotypes |
| topic | Streptococcus pneumoniae phase variation pneumococcus |
| url | https://journals.asm.org/doi/10.1128/mSphere.00386-17 |
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