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Genetic Basis Underlying the Hyperhemolytic Phenotype of Streptococcus agalactiae Strain CNCTC10/84
- Source :
- J Bacteriol
- Publication Year :
- 2020
- Publisher :
- American Society for Microbiology, 2020.
-
Abstract
- Streptococcus agalactiae (group B streptococcus [GBS]) is a major cause of infections in newborns, pregnant women, and immunocompromised patients. GBS strain CNCTC10/84 is a clinical isolate that has high virulence in animal models of infection and has been used extensively to study GBS pathogenesis. Two unusual features of this strain are hyperhemolytic activity and hypo-CAMP factor activity. These two phenotypes are typical of GBS strains that are functionally deficient in the CovR-CovS two-component regulatory system. A previous whole-genome sequencing study found that strain CNCTC10/84 has intact covR and covS regulatory genes. We investigated CovR-CovS regulation in CNCTC10/84 and discovered that a single-nucleotide insertion in a homopolymeric tract in the covR promoter region underlies the strong hemolytic activity and weak CAMP activity of this strain. Using isogenic mutant strains, we demonstrate that this single-nucleotide insertion confers significantly decreased expression of covR and covS and altered expression of CovR-CovS-regulated genes, including that of genes encoding β-hemolysin and CAMP factor. This single-nucleotide insertion also confers significantly increased GBS survival in human whole blood ex vivo. IMPORTANCE Group B streptococcus (GBS) is the leading cause of neonatal sepsis, pneumonia, and meningitis. GBS strain CNCTC10/84 is a highly virulent blood isolate that has been used extensively to study GBS pathogenesis for over 20 years. Strain CNCTC10/84 has an unusually strong hemolytic activity, but the genetic basis is unknown. In this study, we discovered that a single-nucleotide insertion in an intergenic homopolymeric tract is responsible for the elevated hemolytic activity of CNCTC10/84.
- Subjects :
- Histidine Kinase
Virulence Factors
Virulence
Biology
medicine.disease_cause
Hemolysis
Microbiology
CAMP test
Streptococcus agalactiae
03 medical and health sciences
Bacterial Proteins
Streptococcal Infections
medicine
Humans
Point Mutation
Promoter Regions, Genetic
Molecular Biology
Gene
030304 developmental biology
Regulator gene
0303 health sciences
Base Sequence
Strain (chemistry)
030306 microbiology
Streptococcus
Gene Expression Regulation, Bacterial
Phenotype
Research Article
Subjects
Details
- ISSN :
- 10985530 and 00219193
- Volume :
- 202
- Database :
- OpenAIRE
- Journal :
- Journal of Bacteriology
- Accession number :
- edsair.doi.dedup.....80be0c8996d7ccc33810fb14a398df76