INF1 - E. BACTERIA AND PATHOGENICITY-COVERED Flashcards
1
Q
what are prokaryotes
A
- no defined nucleus
- smaller (<1-2 microns)
- bacteria
2
Q
what are eukaryotes
A
- defined nucleus a
- bigger (10-100+ microns)
- animals, plants, fungi, protozoa, algae
3
Q
what is unique to bacterial cells compared to ours
A
peptidoglycan cell wall
4
Q
what is peptidoglycan made of
A
- N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) pentapeptide (glycan monomer)
- D-alanine in postions 4 and 5
- additional pentaglycine sequence in some gram-+ve bacteria - attached to lysine at position 3
- glycan monomers transported across cytoplasmic by bacteoprenol
- monomers joined through glycosidic bonds by glycerotransferases to make polymer chains
- polymer chains cross linked through peptide bonds between third positions on one polymer and D-alanine of another chain by transpeptidases
5
Q
describe the gram-positive cell wall
A
- 80-90% peptidoglycan
- gram stain dyes cell blue/purple
- teichoic acid embedded in wall which facilitates movement in to and out of bacterium (can stimulate inflammatory response)
- proteins embedded in the wall: adhesins help with adhesion to host cells and surfaces
- enzymes aid nutrient acquisition and can damage host cells and tissue
- permeable to most antibiotics some species sporulate (bacilli)
6
Q
examples of gram-positive bacteria
A
- Staphylococcus aureus
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Clostridium difficile
7
Q
describe the gram-negative wall
A
- 10-20% peptidoglycan
- gram dye stains cell pink
- has an outer membrane which is linked to peptidoglycan by lipoprotein anchor
- rich in lipopolysaccharide (endotoxin) which allows entry of molecules into cell (can stimulate strong inflammatory response)
- proteins like enzymes and adhesions
- impermeable to many antibiotics
- no sporulating bacteria
8
Q
examples of gram-negative bacteria
A
- Escherichia coli
- Salmonella enterica
- Campylobacter jejuni
- Vibrio cholera
- Heliobacter pylori
- Chlamydia trachomatis
9
Q
what does lipopolysaccharide consist of
A
lipid A
core region oligosaccharide and other molecules
O-polysaccharide tail (O antigen)
10
Q
describe the acid-fast cell wall (mycobacterium tuberculosis)
A
- mostly made of mycolic acid (glycolipid) - Ziel-Neelson stain (red)
- small amount of peptidoglycan
- mycolic acids impede entry of molecules so slow growing bacteria but greater resistance to chemical agents and enzymes
- this is why you need antibiotics for months due to hard access across cell wall
11
Q
differences between prokaryotic and eukaryotic cells
A
- fimbriae and pili in prokaryotic cells
- capsules and slime layers in some bacteria
(form biofilms: collection of micro-organisms surrounded by the slime they secrete and attached to an inert or living surface and hence antimicrobials can’t penetrate) - flagella in some bacteria
12
Q
what are endospores
A
- formed by some gram+ve bacteria due to ‘starvation’ or adverse environment, can cause infection
- exist in state of dormancy, can persist for long periods
- highly resistant to extreme of temp, pH, desiccation, radiation, chemical agents (ie - antibiotics, disinfectants)
13
Q
what is the microbiome
A
- bacteria in/on our body which don’t cause damage and can be beneficial or protective
- unique in everyone
- low virulence bacteria ie, low risk of causing disease
- reduce risk of colonisation by pathogenic bacteria
- disrupted by overuse/inappropriate use of antibiotics (we need antibiotic stewardship)
14
Q
what is an infection
A
- any microorganism or toxin (ie produced by bacteria and contaminating foodstuff) capable of entering human body and causing harm
- via initial interaction/invasion of epithelial tissue (skin, eye, internal mucosa of airways, gut, genitourinary)
15
Q
what is bacteraemia
A
presence of bacteria in blood
