Bacteria and Biofilms — Lecture Notes

Vocabulary flashcards focusing on oral microbiology, biofilm development, and the pathophysiology of dental caries and periodontal disease based on Dr. Kate Miller's lecture.

Oral Microbiome (Oral Microbiota)

A diverse community of microorganisms in the mouth consisting of approximately $700$ different bacterial species, with any one individual hosting $200-300$ species at a time.

Adhesins (fimbriae)

Surface proteins on bacteria that grab onto specific receptors on host cells using a specific lock-and-key interaction to ensure firm attachment.

Biofilm

A community of multiple bacterial species living together within a sticky extracellular matrix (slime layer) that provides high resistance to antibiotics and can remain dormant.

The Pellicle

A thin protein film made of salivary glycoproteins that sticks to enamel within seconds of cleaning and reaches maximum thickness in $90-120$ minutes.

Pioneer bacteria

The first microbes to attach to the pellicle, primarily consisting of Streptococci species like $Strep.\text{ sanguinis}$, $Strep.\text{ gordonii}$, and $Strep.\text{ mutans}$.

Co-aggregation

The process of secondary colonisation where new bacterial species attach to the existing bacteria already anchored on the tooth surface.

Calculus (Tartar)

Calcified plaque formed when calcium and phosphate salts from saliva deposit into the biofilm, creating a rough surface that requires professional scaling for removal.

Dental Caries

A multifactorial disease involving the breakdown of tooth tissue (enamel and dentine) caused by acid-producing bacteria fermenting carbohydrates.

Demineralisation

The process where acid dissolves minerals such as calcium, phosphate, and carbonate from the hydroxyapatite crystals of the enamel.

Ecological Plaque Hypothesis

The theory that a change in the oral environment (e.g., increased sugar or inflammation) triggers a shift in the microbial community from healthy to disease-associated species.

Glucosyltransferases (GTFs)

Enzymes produced by $S.\text{ mutans}$ that transform sucrose into glucans, which help consolidate the bacterial biofilm.

FoF1 ATPase

A proton pump used by $S.\text{ mutans}$ to express acid tolerance by pumping out protons to survive in low $pH$ environments.

Xerostomia

A condition of dry mouth or low saliva flow that significantly increases the risk of both dental caries and gum disease.

Gingival Crevicular Fluid (GCF)

A fluid that increases during inflammation, providing nutrients for proteolytic, Gram-negative anaerobic bacteria in periodontal pockets.

Gingivitis

The reversible early stage of periodontal disease characterized by gum inflammation, redness, and bleeding in response to plaque accumulation.

Periodontitis

An advanced, inflammatory stage of gum disease affecting the bone and ligament, characterized by a shift to Gram-negative anaerobes and the formation of periodontal pockets.

Red Complex

A group of key bacteria associated with deep periodontal pockets and advanced disease, consisting of $P.\text{ gingivalis}$, $T.\text{ forsythia}$, and T.\text{ denticola.

Dental Unit Waterlines (DUWL)

Tubing within dental equipment where stagnant water can allow biofilms to form, posing risks of infection by pathogens like $Pseudomonas$ and equipment damage.