Bacterial Pathogenicity Flashcards
What are the 4 shapes of bacteria?
Coccus
Bacillus
Coccobacillus
Pleomorphic (mixed)
What type of molecule stabilises the bacterial plasma membrane?
Hopanoids
What makes a bacteria gram positive?
Presence of a peptidoglycan cell wall
What makes a bacteria gram negative?
- Single layer of peptidoglycan
- Presence of an outer membrane with lipopolysaccharides
What do the lipopolysaccharies in the outer membrane do?
Repel cells of the immune system
What is a glycocalyx?
Capsules/slime layers - protects bacteria from the immune system
What are fimbriae?
Pili, used to stick to surfaces
Which type of bacteria stains pink and which stains purple?
Gram +ive = purple
Grame -ive = pink
How many chromosomes do bacteria usually have?
Only one
Typical circular/double stranded and supercoiled
What are plasmids?
Extra-chromosomal circular DNA - usually auxiliary genes
What do plasmids do for the cell?
Provide some sort of advantage, e.g. resistance, virulence, colicin, fertility, degradative
What is the advantage of bacterial genetic variation?
Evolution - can result in increased virulence or resistance to host defences/treatments
What are the 2 mechanisms of bacterial variation?
Mutation (slow) or recombination (fast)
What are symbiotic bacteria?
Bacteria and host gain benefit
What are commensal bacteria?
Bacteria gain benefit but cause no harm to host
What are pathogenic bacteria?
Bacteria gain benefit and cause harm to host (can be obligate or facultative)
What are facultative pathogens?
Opportunistic, normally harmless but have ability to be pathogenic with altered host conditions (e.g. cut on skin)
What is endogenous infection?
Infection from host’s own commensal flora
What is an exogenous infection?
Infection from environment/other hosts
What are the 3 main opportunities for facultative pathogens to infect?
New body site
Altered body site
Reduced defences
