1. Intro to bacterial structure

dental caries

demineralization of enamel that progresses to cavitation, caused by a supragingival dysbiotic biofilm

What type of biofilm is associated with caries?

A supragingival dysbiotic biofilm.

Periodontitis

disease involving subgingival dysbiotic microbial communities on the root surface

What initiates oral dysbiosis in periodontal disease?

Infection with periodontal pathogenic bacteria

What is the oral–gut microbiome axis?

pathway linking oral dysbiosis to changes in the gut microbiome, influencing systemic immune responses.

How does oral dysbiosis contribute to systemic disease?

triggers host immune and inflammatory responses, allowing oral microbes to colonize distant organs or tissues.

consequence of oral microbes colonizing distant organs?

Development of multiple systemic diseases.

What are the two forms of life?

Prokaryotes and eukaryotes.

What organisms are prokaryotes?

Bacteria and Archaea, which have no nucleus.

Prokaryotes have

no nucleus or organelles

eukaryotes?

nucleus and organelles

What did Carl Woese propose?

introduced three domains of life instead of two.

Avg bacterial size

1-3 micrometers

Avg virus size

0.1-0.5 micrometers

Scanning electron microscope can see

bacterial surfaces in detail.

Transmission electron microscopy can see

high resolution internal structures of bacteria

Viruses are NOT

considered cells

Bacteriophages

viruses that infect bacteria

Prokaryotic ribosome

70S

Where is bacterial genetic material

located in the nucleoid region

Most prokaryotic cells are haploid/diploid

haploid meaning they have a single set of chromosomes.

Nucleoid region

not membrane enclosed, contains single circular chromosome

Bacterial ribosome components

50S and 30S = 70S

Cytoplasmic inclusion bodies

used by bacteria to store nutrients, waste products, and other substances.

Phospholipid bilayer

a double layer of phospholipids that forms the cell membrane, with NO STEROLS

Peptidoglycan is made of which 2 components

NAG and NAM

NAG and NAM are joined by which enzyme to make peptidoglycan

transglycosylase

Transglyosylase

forms a β1-4 linkage between NAG and NAM to create peptidoglycan `

Main function of peptidoglycan

creates rigitiy and structural support for bacterial cell walls.

Bacterial transpeptidase enzyme

cross-links peptide chains to strengthen peptidoglycan

Gram positive cell wall

Contains thick peptidoglycan layer and teichoic/lipoteichoic acids

Gram negative cells wall

thin peptidoglycan layer surrounded by an outer membrane containing lipopolysaccharides.

Periplasmic space

the aqueous space between the inner and outer membranes in Gram-negative bacteria, containing enzymes and proteins (antibiotic resistance)

Major structural component of penicillin

β lactam ring

β-lactamase

enzyme produced in periplasmic space which cuts βlactam ring of antibiotics like penicillin

Lipopolysaccharide (LPS)- O antigen

antigenic part involved in immune response

Lipopolysaccharide (LPS)- lipid A

endotoxin part of LPS that anchors in to cell membrane

LPS. may induce

fever or shock

Lysozyme is found in

saliva and tears, it helps destroy bacterial cell walls.

Lysozyme MOA

Hydrolyzes β1-4 bond between NAG & NAM

Penicillin MOA

inhibits transpeptidase so no peptidoglycan synthesis `

Penicillin with gram + bacteria

protoplast (removal of entire cell wall)

penicillin with gram - bacteria

spheroplast (partial removal of cell wall)

Which bacteria is more susceptible to penicillin

gram +

Gram + bacteria stained

purple

Gram - bacteria stained

pink

Pathogenicity

Ability to cause disease

Virulence factors

Attributes that increase disease severity or ability to become infective

Glycocalyx (slime layer)

virulence factor that allows for adhesion