Related Experiment Video
Updated: Dec 13, 2025
High-throughput Measurement of Plasma Membrane Resealing Efficiency in Mammalian Cells
Published on: January 7, 2019
Cytotoxic property of Streptococcus mitis strain producing two different types of cholesterol-dependent cytolysins
Atsushi Tabata1, Hisashi Ohkuni2, Haruka Hino3
1Department of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1 Minamijousanjima-cho, Tokushima 770-8513, Japan; Department of Biological Science and Technology, Life System, Institute of Technology and Science, Tokushima University, 2-1 Minamijousanjima-cho, Tokushima 770-8513, Japan.
Abstract:
Streptococcus mitis strain Nm-65 secretes an atypical 5-domain-type cholesterol-dependent cytolysin (CDC) called S. mitis-derived human platelet aggregation factor (Sm-hPAF) originally described as a platelet aggregation factor. Sm-hPAF belongs to Group III CDC that recognize both membrane cholesterol and human CD59 as the receptors, and shows preferential activity towards human cells. Draft genome analyses have shown that the Nm-65 strain also harbors a gene encoding another CDC called mitilysin (MLY). This CDC belongs to Group I CDC that recognizes only membrane cholesterol as a receptor, and it is a homolog of the pneumococcal CDC, pneumolysin. The genes encoding each CDC are located about 20 kb apart on the Nm-65 genome. Analysis of the genomic locus of these CDC-encoding genes in silico showed that the gene encoding Sm-hPAF and the region including the gene encoding MLY were both inserted into a specific locus of the S. mitis genome. The results obtained using deletion mutants of the gene(s) encoding CDC in Nm-65 indicated that each CDC contributes to both hemolysis and cytotoxicity, and that MLY is the major hemolysin/cytolysin in Nm-65. The present study aimed to determine the potential pathogenicity of an S. mitis strain that produces two CDC with different receptor recognition properties and secretion modes.
Insights
Streptococcus mitis Nm-65 produces two distinct cholesterol-dependent cytolysins (CDCs): Sm-hPAF and mitilysin (MLY). MLY is the primary hemolysin, with both CDCs contributing to the strain's pathogenicity.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Streptococcus mitis Nm-65 secretes two cholesterol-dependent cytolysins (CDCs): Sm-hPAF (Group III) and mitilysin (MLY, Group I).
- Sm-hPAF utilizes cholesterol and CD59, while MLY recognizes cholesterol, exhibiting differential receptor binding.
- These CDC genes are located separately on the Nm-65 genome, suggesting specific insertion events.
Purpose of the Study:
- To investigate the pathogenic potential of S. mitis Nm-65 producing two CDCs with distinct receptor specificities.
- To elucidate the roles of Sm-hPAF and MLY in the hemolytic and cytotoxic activities of S. mitis Nm-65.
Main Methods:
- Genomic analysis to identify CDC genes and their loci.
- Construction and analysis of deletion mutants for each CDC gene.
- Assessment of hemolytic and cytotoxic activities of wild-type and mutant strains.
Main Results:
- Both Sm-hPAF and MLY contribute to the hemolysis and cytotoxicity of S. mitis Nm-65.
- Mitilysin (MLY) was identified as the major hemolysin and cytotoxin produced by the Nm-65 strain.
- Deletion mutants confirmed the individual contributions of each CDC to the strain's virulence factors.
Conclusions:
- S. mitis Nm-65 possesses a complex virulence system involving two distinct CDCs.
- The dual CDC production enhances the hemolytic and cytotoxic capabilities of this S. mitis strain.
- Understanding these CDCs is crucial for assessing the pathogenicity of S. mitis infections.
More Related Videos
14:29Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy
Published on: October 1, 2012
09:25Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells
Published on: August 19, 2016
