Lecture 1 Flashcards
Prions
Protein Only disease Infective proteins with no nuclein acid that reproduce only in a living cell.
Recent new diseases
Legionellosis Lyme Disease AIDS
Recent new pathogens
Prions SARS - a syndrom caused by a virus
Recent new problems
Nosokomial infections, a disease that originates inside a hospital. Immunosupressed patients.
Bacterial cell ESSENTIAL components ACCESSORY COMPONENTS
Essential components:
Cell wall
Membrane
Cytoplasm
Ribosomes
Nucleoid - One long, circular double stranded DNA molecule. Super coiled. Usually about 1mm in total length with about 3500 genes.
(haploid because they reproduce asexually, they just need to divide the DNA and each copy goes to each new cell)
Accessory components:
Cilia
Fimbrias - can be sex fimbrias, or simple fimbrias for adhesion
Capsule
Flagellum
Gram positive bacteria cell wall
1) Cell Membrane
2) Periplasmic Space
3) Cell wall
Thick layer of cross linked Peptidoglycans form a rigid structure, which protects against osmotic pressure.
Teichoic acid fibers extend out and are the major G+ surface antigen.
does not contain LPS
Gram negative bacteria cell wall
1) Inner cell membrane
2) Periplasmic space, surrounding the Single Peptidoglycan layer
3) Outer cell membrane contains Porins, and bears Lipopolysaccharide LPS
-The Lipid A portion of LPS is responsible for the toxic/inflammatory properties of LPS.
does not contain teichoic acid.
What is the site of action of aminoglycoside drugs: Erythromycin, tetracycline, chloramphenicol
The ribosomes
What is the site of action of penicillin?
The Peptidoglycans of the G+ cell wall.
Penicillin inhibits the cross linking enzyme, transpeptidase.
What is the function of the periplasmic space
Contains enzymes for the metabolism/hydrolysis of large substrates and things that would be toxic to the cell
- ex. DNAses, nucleases.
- also cell wall enzymes
b-lactam antibiotics such as penicillin need to interact with periplasmic space enzymes in order to have their effect.
What are Fimbriae
Thin, short hairlike appendages 1-20uM
Usually many of them if present.
On GN bacteria, notable on enterobacteriaceae and neisseria
Are not mobile.
Are composed of the protein pilin.
Also called common pili as opposed to just ‘pili’ which means sex pili.
Are antigenic and haemagglutinating.
What are four significant things about the bacterial capsule?
1) It determines virulence of many bacteria, since it can affect the phagocytosis by immune cells.
2) Allows for bacterial identification by antibodies. For example, by the Quellung (Swelling) Reaction.
3) Polysaccharides from the capsul are used as the antigens in some vaccines
4) Is involved in bacteria adherence to host tissues.
Quellung Reaction
What is the bacterial capsule made of?
A gel layer of polysaccharide which covers the whole bacteria and is often larger than the bacteria itself. (_not_ LPS)
A single bacteria species can have many serologic types (ie what antibodies the specific strain generates) which can depend on the specific sugar components in the capsule.
Anthrax bacillus is unique, its capsule is polymerized D-glutamic acid.
What is the glycocalix or slime layer?
It is a polysaccharide layer similar to the capsule, but it is more loosely associated, can be easily removed from the bacteria by centrifugation.
Is involved in bacterial adherence
What are bacterial Granules?
Storage organelles which stain characteristically with certain dyes.
ex. Volutin granules, polymerized metaphosphate
How are bacterial spores formed?
Long-living, heat and dessicant resistant, dormant forms of bacteria.
Endospores are formed inside of the bacterial cell itself, after DNA duplication and then assymetric separation, then re-engulfment of the small daughter cell by the larger one, assymbly of the spore outer layers, and then lysis and release of the spore.
Akinetes are very thick walled dormant bacteria, also a type of spore.
What are the steps of the Gram Stain?
What factors affect the Gram Stain?
Steps:
1) Crystal violet 2) Lugol Iodine 3) Alcohol 4) Safranin
Factors affecting it
1) The thickness of the cell wall
2) The pore size
3) The permeability of the cell envelope
