oral microbial ecology l.
Skip this Video
Loading SlideShow in 5 Seconds..
Oral Microbial Ecology PowerPoint Presentation
Download Presentation
Oral Microbial Ecology

Loading in 2 Seconds...

play fullscreen
1 / 20

Oral Microbial Ecology - PowerPoint PPT Presentation

  • Uploaded on

Oral Microbial Ecology. DENT 5301 Introduction to Oral Biology Dr. Joel Rudney. Oral microbial diversity. The “we know what we can grow” bias Emphasis on species recovered from culture Revolutionized by molecular methods for species ID Species signatures in 16S ribosomal RNA sequences

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Oral Microbial Ecology' - abra

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
oral microbial ecology

Oral Microbial Ecology

DENT 5301

Introduction to Oral Biology

Dr. Joel Rudney

oral microbial diversity
Oral microbial diversity
  • The “we know what we can grow” bias
    • Emphasis on species recovered from culture
  • Revolutionized by molecular methods for species ID
    • Species signatures in 16S ribosomal RNA sequences
    • Does not require microbial culture
  • Perhaps 700+ distinct oral species
    • Most have never been cultured
    • Gram+, Gram-, cocci, rods, filaments, spirochetes, etc.
    • Include some very exotic taxonomic groups (Archea)
      • Termite guts and other extreme environments
    • Fungi and viruses are all in the mix
biofilm on tooth surfaces
Biofilm on tooth surfaces

Emerging trends in Oral Care

Biofilm Revolution

Scientific American, 2002

The “natural habitat” of most oral bacteria

A structured multi-species community

Bacteria embedded in matrix with water channels

Attachment - growth - ecological succession - maturation

adherence and microcolonies
Adherence and microcolonies

Biofilms are initiated by bacterial adherence to a surface

Isolated cells bind receptors on surface

Replication (growth) is required to form single-species microcolonies

Growth requires “quorum sensing”

In vitro biofilm (and cat) by Streptococcus sanguinis

SEM by Tracy Grossman

in vitro biofilm in depth
In vitro biofilm - in depth


ecological succession
Ecological succession

3° colonizers (Gram-)

Porphyromonas gingivalis

2° colonizers (Gram-)

Bridge species - F. nucleatum

Bind other bacteria

1° colonizers (Gram+)

Streptococci bind pellicle proteins from saliva

DENT 5302

Kolenbrander et al. 2002, Microbiol Mol Biol Rev 66:486

inter bacterial coaggregation



Inter-bacterial coaggregation

Edwards, Grossman, and Rudney, 2007, Oral Microbiol Immunol, in press

Streptococcus cristatus coaggregating with F. nucleatum

- adhesins interacting with receptors

Coaggregation is important in ecological succession

Fusobacterium nucleatum is considered a bridge species because it is a promiscuous coaggregator

interspecies collaboration o 2
Interspecies collaboration - O2

Streptococcus cristatus

Facultative species

Can live w/ or w/o O2

Uses up O2 when available

Fusobacterium nucleatum

Robust anaerobe

Binding strep improves survival when O2 is present

Porphyromonas gingivalis

Sensitive anaerobe

Coaggregation essential to survival when O2 is present

In vitro three-species biofilm made by replicating an ecological succession

Grossman, Edwards, and Rudney 2006 AADR

inter species competition
Inter-species competition

Many oral species produce substances that can kill closely related competitors

Overlay experiment:

Streptococcus sobrinus lawn

Spotted with wild-type Streptococcus mutans strain producing mutacins I and IV

Single knockout mutants

Double knockout mutants

Measure zones of growth inhibition

Picture courtesy of Dr. Jens Kreth

inter species communication
Inter-species communication

Streptococci ferment CHO

Excrete lactic acid

Veillonella use lactate made by Strep for nutrition

They are biofilm buddies

Strep can make amylase

Starch-digesting enzyme

Enhances lactate excretion

Veillonella send a chemical signal to activate transcription of Strep amylase gene

Bacteria sense other species

Egland, Paul G. et al. (2004) Proc. Natl. Acad. Sci. USA 101, 16917-16922

oral ecological zones
Oral ecological zones
  • Mostly the same species present, but proportions differ
  • High biomass sites
    • Non-shedding surfaces
      • Supragingival tooth surfaces
      • Subgingival tooth surfaces
    • Shedding surface
      • The tongue
  • Low biomass (reservoir) sites
    • Shedding oral mucosal surfaces
      • Buccal, palate, external gingiva, floor of mouth
  • Saliva as a transitional zone
subgingival tooth surfaces
Subgingival tooth surfaces

Narrow crevice between gingival epithelium and cementum

Low oxygen tension

Favorable for Gm- anaerobes

Major site for interaction between bacteria and host tissues

Species mix varies between each side and the center

- distinct microenvironments

Emerging trends in Oral Care

Biofilm Revolution

Scientific American, 2002

the tongue
The tongue
  • A shedding surface
  • Cells slough off
  • BUT
  • Structure includes crypts and fissures
  • Favorable for Gm- anaerobes
mucosal reservoir sites
Mucosal reservoir sites
  • Smooth exfoliating surfaces
    • How do bacteria keep from being swept away?
  • Some oral species can invade epithelial cells
    • Requires communication between bacteria and cells
    • Bacteria “subvert” the cell to take them in
      • Take control of the cytoskeleton
      • Can live and grow inside
    • Can direct the cell to export them to other cells
  • Multi-species intracellular flora resembles mixed biofilm
invaded buccal cells
Invaded buccal cells

Rudney, Chen, and Zhang 2005 J Dent Res 84:1165

collaborative invasion
Collaborative invasion

Tissue culture experiment

F. nucleatum invades epithelial cells

S. cristatus does not invade cells

After coaggregation, S. cristatus is carried inside by F. nucleatum

Edwards, Grossman, and Rudney 2006, Infect Immun 74: 654

salivary transport
Salivary transport
  • Quorum sensing tells bacteria when to grow, and when it’s time to go
  • Bacteria at the outer surface of mature biofilms are signaled to detach and become planktonic
  • The goal is to find a new home
  • Different genes are active in planktonic and biofilm states

Saliva is the transport medium for planktonic oral bacteria

-They don’t grow unless they encounter another surface

Exfoliated epithelial cells in saliva can also transport bacteria

-A protected environment

bacteria during the life cycle
Bacteria during the life cycle
  • Oral colonization begins in the birth canal
    • Reservoir populations on the tongue and mucosa
    • Established during infancy - include anaerobes
  • Tooth eruption provides non-shedding surfaces
    • The “window of infectivity” concept
    • Colonization from reservoir sites and caregiver saliva
  • Hormonal shifts - puberty and pregnancy
    • Can alter proportions of Gm- anerobes
  • Complete loss of teeth shifts flora towards infant state
    • Dentures restore supragingival non-shedding sites
    • Implants restore supra- and subgingival sites
relationships with the host
Relationships with the host
  • Host defenses in the mouth
    • Epithelial cells
      • Barrier function
      • Innate immunity - sensors (Toll-like receptors)
        • Inflammatory mediators, antimicrobial peptides
    • Salivary antimicrobial factors - DENT 5302
    • Mucosal antibodies (secretory IgA)
    • Cell-mediated immunity (T-cells)
  • In most cases, host defenses tolerate oral bacteria
    • The predominant relationships are commensal
are there true oral pathogens
Are there true oral pathogens?
  • Classic concept of a pathogen
    • Not normally present
    • Produces “virulence factors”
      • Damage host directly (e.g. toxins)
      • Induce host to damage itself (immune responses)
  • Presumed oral pathogens don’t quite fit that model
    • Normally present throughout life
    • Damage requires presence in large numbers
  • Ecological concept of oral microbial diseases
    • Ecological shifts lead to changes in proportions
    • Balance shifts in favor of “pathogens”/disease