Week 3 & 4 review Flashcards
Microbe
all types of microscopic organisms
bacterium/bacteria
smallest, simplest living organisms
Cell envelope
a complex, multilayered structure that protects the microorganism from external environment
Gram staining
classifies bacteria as gram positive or negative
Gram positive
single, thick, multilayered, mesh-like, wall composed of peptidoglycan, thick layer lies above cytoplasmic membrane that faces the interior of the cell
appears purple
Gram negative
two membranes:
1) outer membrane faces external environment, composed of proteins and lipoplysacchrides (endotoxin)
2) between outer and cytoplasm, is a thin cell wall compared of peptiglycan - does not absorb purple appears red
Biofilm
complex microbial community, embedded within an extracellular self-protective matrix, that adheres to a living or nonliving surface
oral biofilm
3D community embedded in a protective matrix that consists of microbial metabolic products or host components
commensal bacteria
part of normal flora, symbiotic relationship with host
dysbiosis
microbial imbalance in body
vertical transmission
saliva form parent to child (different generations)
horizontal transmission
sharing saliva from same generation
Acquired salivary pellicle
within seconds, salivary film forms composed of salivary glycoproteins and antibodies
coaggregation
process with genetically distinct bacteria become attached to another
extracellular protective matrix
once firmly attached, microbes will secrete an enveloping protective substance
Microbial blooms
periods when specific groups will grow rapidly; fast; begin to grow away from tooth
Mushroom-shaped micro colonies
microbes cluster together that are attached to tooth surface at a narrow base - results in complex collection of different microbes linked together
fluid channels
penetrate the ECM, direct fluids around biofilm, brining nutrients and oxygen, and carry waste away.
quorum sensing
communication occurs when biofilm release and sense small proteins (signalling proteins)
tooth-associated plaque biofilms
bacteria attached to tooth surface
examples: Streptococcus mitis, S. Sanguis, Actinomyces viscosus
- Cocci and rods dominate tooth - associated plaque biofilms
tissue-associated plaque biofilms
bacteria that adhere to the epithelium
example: spirochetes and flagellated and gram negative cocci and rods
- Streptococcus oralis, S. intermedius, porphyromonas gingivalis, pevotella intermedia, tannerella forsythia, fusobacterium nucleatum
unattached bacteria
periodontal pocket also contains free-floating unattached bacteria
Non-specific plaque hypothesis
the accumulation of bacterial biofilms lead to periodontal disease (historical)
specific plaque hypothesis
the specific pathogenic bacteria and their products in the biofilm lead to periodontal disease (historical)
- Orange and red complexes - major etiologic agents of periodontal disease
- Yellow, green, blue, and purple complexes - compatible with gingival health
ecological plaque hypothesis
accumulation of nonspecific bacteria tiggers the host inflammatory response which alters the local environment
microbial homeostasis - host response hypothesis
although they cause inflammatory response leading to gingivitis, the pathogenic bacteria are not direct cause of destruction of tissues seen in periodontitis
keystone pathogen - host response hypothesis
expands on other theory: that a specific bacterial species is key in creating the shift from symbiotic microbes to dysbiotic microbes in the biofilm community. In turn, the dysbiotic biofilm community triggers the uncontrolled host response that results in damage to the periodontal tissues
A. actinomycetemcomitans (Aa)
Gram -
Rod shaped
Nonmotile
Facultative (live in multiple environments)
Late colonizer
Mainly subgingival
Found in periodontal disease
S. Mitis
Gram positive
Cocci shaped
Non-motile
Early colonizer
Tooth associated plaque
Facultative
Found in both health and disease (but not associated with periodontitis)
P. gingivalis
Includes vertical transmission
Gram negative
Obligate anaerobes (doesn’t like oxygen)
Tissue associated plaque
Considered keystone species (cause shift to disease via host immune response)
It is Rods
intermediate colonizers
F. nucleatum
Gram negative
Rod shaped bacterium
Non-motile
Intermediate colonizer
Tissue associated plaque
Facultative
Found in periodontal disease
Found in amniotic fluid
T. forsythica
Gram negative
Obligate anaerobes
Rods
Found in periodontal disease
Non motile
Member of the red complex
Bridge between the early and late colonizing bacteria of dental plaque
Tissue associated
Late colonizer (likes to attach to p. Gingivalis esp)
S. oralis
Gram positive
Cocci
Non-motile
Early Colonizer
Facultative
Mostly associated with health
tissue associated
A. viscous
Gram positive
Rods
Facultative anaerobes
Non-motile
Early colonizer
Tooth-associated plaque
- health certain conditions dental plaque
S. sanguis
Gram positive
Cocci
Motile
Early colonizer
Tooth associated plaque
Facultative
Can be found in both health and disease, but more abundant in health
P. intermedia
Gram negative
Rod shaped bacterium
Non motile
Intermediate colonizer
Tooth associated plaque
Obligate anaerobic
Found in periodontal disease (aggressive necrotizing periodontitis
C. gingivalis
Gram negative
Bacilli
Motile
Tooth associated plaque
Facultative
Present in both health and periodontal disease; found in greater numbers in disease states
aerobic, anaerobic, facultative anaerobic
aerobic - need O
anaerobic - cant live with O
Facultative - can exist with or without O
Formation time lines:
minutes - free floating attach
2-4 hours - strongly attached micro colonies
6-12 hours - produce matrix
2-4 days - fully mature biofilm colonies recover from disruption
Blocking-protective matrix
prevents large molecules and inflammatory cells from penetrating deeply into biofilm
mutual protection
antibiotic resistant Bactria secrete protective enzymes to protect neighbouring bacteria
5 stages of polymicrobial biofilm formation
1) initial attachment to pellicle
2) permanent attachment
3) maturation phase I
4) maturation phase II
5) dispersion
Stage 1: Initial attachment
- Pellicle composed of glycoproteins and antibodies (always there)
- Protects enamel from acid activity
- Intermediate and late bacterial colonizers are unable to adhere to tooth until early colonizers do
Stage 2: permanent attachment
- Microbes able to Withstand hydrodynamic forces attain permanent attachment
- Produce substances to attract other microbes to the community
Stage 3 - Maturation phase I: self-protective matrix formation
- Firmly attached bacteria surrounding protective secrete surrounding protective substance called extracellular protective matrix
- Consists of proteins, glycolipids, bacterial DNA
- Protects against host-generated immune defenses (chronic diseases is established)
Step 4: Maturation II: mushroom-shaped microcolonies
- Microbes cluster together and form mushroom-shaped microcolonies that attach to the tooth by a narrow base
- Grow at accelerated rate, thicker
- Fluid channels penetrate the protective matrix
- Communication (cell-to-cell) via chemical signals
stage 5: Dispersion: escape form the matrix
Microbes disperse from the colony to spread and colonize other tooth surfaces
Early colonizers
- Streptococcal species can attach to the tooth pellicle and to each other
- Other early colonizers cannot attach to the pellicle but can congregate with the strep
intermediate and late colonizers
- Must join in proper sequence
- Periodontal pathogens are late colonizers of biofilm
Biofilm components
- Mainly Microorganisms
- Minor: carbohydrates, salivary components/proteins, desquamated cells, exudate, bacteria by-products (enzymes), inorganic products (Ca, Fl, K, etc)
