1037DOH - Oral Microbiology and Cariology

another one for my goats:) made by ambereen just for you ;)

what is a microbiome?

• the collection of genomes from the total culturable and unculturable microorganisms

• includes biomolecules within a defined habitat

what is a microbiota?

• total collection of resident microbes within the microbiome

what are two features of microorganisms you can use classify and categorise them? briefly describe what these are

• phenotype

  • observable characteristics/traits of an organism

• genotype

  • organism’s complete set of heritable genes/genes that can be passed down from parents to offspring

what are the three domains of life?

1. bacteria (prokaryotes)

2. archaea (prokaryotes)

3. eucarya (eukaryotes)

describe the possible shapes and typical size of bacteria (MORPHOLOGY OF BACTERIA)

shapes

• cocci (spherical)

• bacilli (rod shapes)

• spirochaetes (helical)

• pleomorphic (appear as both cocci and bacillary forms)

size

• 0.2 - 5 µm

describe the flagella structure on bacteria

• motile - whip like filaments

• made of flagellin (a type of protein)

• monotrichous - single + one ended

• lopotrichous - many + one ended

• peritrichous - all over outer surface

what are fimbriae and pili on bacteria?

• pilin is a protein

• both are fine, hair-like short structure

• they mediate adhesion of bacteria to receptors on host (human) cell surface

what is the glycoalyx? (bacteria)

• polysaccharide coating covering bacteria’s outer surface

• allow adhesion to structures - eg teeth, oral mucosa, heart valves and catheters

• contribute to formation of biofilms

• eg streptococcus mutans - contributes to dental caries

what is the capsule layer around bacteria?

• amorphous gelatinous layer surrounding bacteria

• polysaccharide formed - may also contain protein

• polysaccharides vary between bacteria and within a species (serological type)

what is the cell wall in bacteria?

• multi-layered structure

• allow rigidity

• porous and permeable to substances with a low molecular weight

• inner layer is peptidoglycan (protein + sugar)

• inner layer varies in thickness and chemical composition (depending on gram-staining property of the bacteria)

describe gram positive, gram negative stains and LPS

gram positive

• dark blue/purple stain

• indicates thicker peptioglycan layer (inner cell wall)

gram negative

• pink stain

• indicates thinner peptidoglycan layer

• indicates complex outer membrane (including lipopolysaccharide (LPS), lipoprotein, and phospholipids, and porins (transportation of molecules)

LPS

• toxic (endotoxin)

• released when cell lysed

describe the cytoplasmic membrane of bacteria

• phospholipid bilayer

  • similar to eukaryotic cells, but bacterial ones dont normally contain sterols

• allows…

  • active transport + selected diffusion of molecules in and out of the cell

  • cell wall precursors synthesis

  • secretion of enzymes and toxins

  • electron transport

  • oxidative phosphorylation (in aerobic species)

• has supporting receptors and other proteins of the

  • chemotactic and

  • sensory transduction systems

describe aerobes, facultative aerobes and anaerobes

aerobes

• organism able to live and reproduce only in the presence of free oxygen

facultative aerobes

• grow either with or without free oxygen

anaerobes

• grow in absence of free oxygen

• those that grow only in absence of oxygen are called obligate/strict anaerobes

describe the cytoplasm structure of bacteria

• thick solution (amorphous matrix)

• fills each cell

• enclosed by cytoplasmic membrane

• mainly composed of water, ions, metabolites and proteins

• structures:

  • nuclear material

  • ribosomes

• in eukaryotes, cytoplasm includes all of the material inside the cell and outside the nucleus

describe the nuclear material (nucleoid) of bacterial DNA

• single, supercoiled and circular chromosome

• 2000 genes

• 1mm long

• undergoes semi-conservative replication bidirectionally from a fixed point

describe the nuclear material (nucleoid) of eukaryotic DNA

• contained within the nucleus

describe function of ribosomes

• in bacterial (prokaryote) ribosomes are in the cytoplasm

• in eukaryotes, ribosomes are attached to the rough endoplasmic reticulum

• facilitate protein synthesis

what is E. coli’s full name?

escherichia coli

what is S. mutan’s full name?

streptococcus mutans

name the 3 anaerobic bacterial species identified in carious coronal dentine (GRAM POSITIVE)

1. peptostreptococcus (COCCI)

   • P. anaerobius

   • P. parvulus

   • P. micros

2. eubacterium (RODS)

   • E. alactolticum

   • E. aerofaciens

   • E. saburreum

3. propionibacterium

   • P. acnes

   • P. avidum

   • P. lymphophilum

name the 3 facultative bacterial species identified in carious coronal dentine (GRAM POSITIVE)

1. streptococcus (COCCI)

   • S. mutans

   • S sobrinus

   • S. intermedius

2. actinomyces (RODS)

   • A. israelii

   • A. odontolyticus

3. lactobacillus (RODS)

   • L. casei

   • L. plantarum

   • L. minutus

name 4 gram negative anaerobic bacterial species identified in carious coronal dentine

1. fusobacterium nucleatum (RODS)

2. porphyromonas (RODS)

3. prevotella (RODS)

4. veillonella (COCCI)

describe fungi

• eukaryotic, single-celled microorganisms

• genus Candida yeasts are pathogenic

describe viruses

• not living

• can infect all types of life forms

• exist in form of independent particles or virions

• DNA or RNA is their genetic material

• shapes range from simple helical/icosahedral forms to complex structure

• about 1/100th the size of bacteria

when infected with a virus, a ____ cell is forced to rapidly produce thousands of identical copies of the original ______

1. host

2. virus