Related Experiment Video

Updated: Jun 1, 2026

Porphyromonas gingivalis as a Model Organism for Assessing Interaction of Anaerobic Bacteria with Host Cells
12:16

Porphyromonas gingivalis as a Model Organism for Assessing Interaction of Anaerobic Bacteria with Host Cells

Published on: December 17, 2015

The pathogenic persona of community-associated oral streptococci

Sarah E Whitmore1, Richard J Lamont

  • 1Center for Oral Health and Systemic Disease, School of Dentistry, University of Louisville, Louisville, KY 40202, USA.

Molecular Microbiology
|June 4, 2011
PubMed

Insights

Mitis group streptococci (MGS) are common in the mouth but can act as accessory pathogens. They support the growth of harmful bacteria like Porphyromonas gingivalis, increasing oral disease risk.

Area of Science:

  • Oral microbiology
  • Bacterial pathogenesis
  • Microbial community dynamics

Background:

  • Mitis group streptococci (MGS) are prevalent in the oral cavity and typically linked to oral health.
  • However, MGS possess traits that promote the development of pathogenic oral communities.
  • They facilitate the attachment of more virulent bacteria, such as Porphyromonas gingivalis.

Purpose of the Study:

  • To investigate the role of MGS in the formation of pathogenic oral microbial communities.
  • To understand the mechanisms by which MGS contribute to the virulence of other oral bacteria.
  • To evaluate the pathogenic potential of MGS within heterotypic communities.

Main Methods:

  • Analysis of MGS adherence to tooth surfaces.
  • Investigation of interspecies signaling systems (e.g., AI-2, contact-dependent mechanisms).
  • Study of signal transduction pathways in P. gingivalis (Ltp1, CdhR) and phenotypic responses (hemin uptake, gingipain activity).
  • Assessment of pathogenicity in animal models using mixed-species communities.

Main Results:

  • MGS rapidly adhere to teeth, serving as a foundation for pathogenic bacteria.
  • MGS support the growth and virulence of pathogens like P. gingivalis and Aggregatibacter actinomycetemcomitans through resource partitioning and interspecies signaling.
  • Pathogenic responses in P. gingivalis are regulated by MGS-induced signaling pathways.
  • Mixed MGS-pathogen communities exhibit increased pathogenicity in animal models compared to single species.

Conclusions:

  • MGS contribute to oral pathogenicity not as primary pathogens, but as 'accessory pathogens'.
  • Their pathogenic potential is realized through interactions within polymicrobial communities.
  • Understanding these interactions is crucial for addressing oral diseases driven by complex microbial consortia.

Related Concept Videos

Determinants of Bacterial Pathogenicity and Virulence01:20

Determinants of Bacterial Pathogenicity and Virulence

Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
Streptococcal Pharyngitis01:27

Streptococcal Pharyngitis

Streptococcal pharyngitis, commonly known as “strep throat,” is an acute infection of the oropharyngeal tissues caused by the Gram‑positive Group A Streptococcus (Streptococcus pyogenes). Transmission occurs primarily through respiratory droplets expelled during coughing, sneezing, or talking.Mechanisms of Host Entry and Immune EvasionUpon entering the host, S. pyogenes adheres to the mucosal epithelial cells of the pharynx via surface proteins, notably lipoteichoic acid and the antiphagocytic...
Staphylococcal Skin Infections01:29

Staphylococcal Skin Infections

Staphylococcus aureus is a Gram-positive coccus that resides harmlessly on the skin and mucous membranes of healthy individuals. When the skin barrier is breached, it can shift from a commensal to an opportunistic pathogen. This transition is facilitated by surface adhesins, such as clumping factor B and S. aureus surface protein G (SasG), which bind to structural proteins, including loricrin and cytokeratin, in the damaged epidermis. Protein A, another key factor, binds the Fc region of...
Bacterial Phylum Spirochaetes01:30

Bacterial Phylum Spirochaetes

Spirochetes, unique bacteria in the phylum Spirochaetes, are gram-negative, motile, tightly coiled, slender, and flexible. They inhabit aquatic sediments and animals, with some causing diseases like syphilis. Spirochetes are classified into eight genera based on habitat, pathogenicity, phylogeny, and characteristics.Their distinctive motility arises from endoflagella, located within the cell’s periplasm. These endoflagella anchor at the cell poles and extend along the cell length, encased by a...
Atypical Pneumonia01:14

Atypical Pneumonia

Atypical pneumonia, often caused by Mycoplasma pneumoniae, is a form of pulmonary infection that differs from the classical presentation of bacterial pneumonia in both its cause and clinical symptoms. Mycoplasma pneumoniae is a pleomorphic bacterium notable for its lack of a rigid cell wall. This structural characteristic imparts resistance to beta-lactam antibiotics and significantly influences the bacterium’s behavior within the human host.Other pathogens responsible for the disease include...
The Oral Microbiota01:27

The Oral Microbiota

The oral microbiome includes a complex ecosystem comprising over 700 microbial species, identified through genomic sequencing and culture-based analyses to date. This community includes a core microbiome, found universally among individuals, and a variable component influenced by environmental factors such as diet, lifestyle, and host genetics. Site-specific conditions, including oxygen gradients, pH levels, and nutrient availability, determine the spatial distribution of these microorganisms...