Related Experiment Video
Updated: May 12, 2026
07:10
A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Core-gene-encoded peptide regulating virulence-associated traits in Streptococcus mutans
Jeong Nam Kim1, Michael J Stanhope, Robert A Burne
1Department of Oral Biology, University of Florida, College of Dentistry, Gainesville, Florida, USA.
Journal of Bacteriology
|April 23, 2013
Summary
A newly discovered gene, SMU.1147, in Streptococcus mutans plays a crucial role in controlling biofilm formation and genetic competence, impacting dental caries development.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Streptococcus mutans is the primary cause of human dental caries.
- High-coverage genome sequencing identified a novel gene, SMU.1147, present in all S. mutans strains but absent in other bacteria.
- SMU.1147 is cotranscribed with genes encoding a two-component system (TCS).
Purpose of the Study:
- To investigate the function of the SMU.1147 gene and its encoded peptide in S. mutans.
- To determine the role of SMU.1147 in virulence-related traits and genetic competence.
- To elucidate the relationship between SMU.1147 and the identified two-component system.
Main Methods:
- Reverse transcription-PCR to analyze gene cotranscription.
- Western blotting to confirm protein expression.
- Construction and phenotypic analysis of SMU.1147 nonpolar mutants.
- Complementation studies to validate gene function.
- Phenotypic evaluation under various stress conditions (low pH, H2O2, high salt) and competence assays.
Main Results:
- A nonpolar mutant of SMU.1147 exhibited reduced biofilm formation, slower growth under stress conditions, and significantly impaired genetic competence.
- The competence defect was linked to reduced expression of competence genes comX and comY.
- Mutants lacking TCS components or all three genes showed altered growth in high salt but otherwise behaved like the wild-type.
- Complementation restored all observed mutant phenotypes.
Conclusions:
- The SMU.1147-encoded peptide is essential for key virulence-related traits in S. mutans.
- SMU.1147 dominantly regulates quorum-sensing pathways governing genetic competence.
- While SMU.1147 is linked to a TCS, its primary role in competence and biofilm appears independent of the TCS components under standard conditions.
Related Concept Videos
01:28Regulation of Bacterial Virulence
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
01:28Gene Regulation in Microbial Communities: Quorum Sensing
Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
01:17Gram-negative Bacterial Protein Secretion Systems
Gram-negative bacteria utilize sophisticated protein secretion systems to transport proteins across their double-membrane envelope into the extracellular environment or host cells. Based on their mechanism of action, these systems are classified into one-step and two-step pathways.One-Step Secretion Systems (Types I, III, IV, and VI)One-step secretion systems bypass the periplasm entirely, forming a continuous channel that spans both the inner and outer membranes:Type I Secretion System (T1SS):...
01:28Peptidoglycan Synthesis
Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan biosynthesis begins in...
01:26Bacterial Translocation and Protein Secretion
Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
01:30Bacterial Signaling
Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell...