Microbiol Flashcards
pathogen
organism that causes or is capable of causing disease
commensal
organism which colonises the host but causes no disease in normal circumstances
opportunist pathogen
microbe that only causes disease if host defences are compromised
virulence/pathogenicity
the degree to which a given organism is pathogenic (how damaging to the host)
asymptomatic carriage
when a pathogen is caried harmlessly at a tissue site causing no disease
2 shapes of bacteria
coccus and bacillus (rod)
bacillus shapes
chain, curved = vibrio, spiral = spirochaete
cocci shapes
cluster, diplococcus, chain
colour of gram pos and negative and why
gram pos = purple neg = pink. due to diff cell struct. pos = thicker peptidoglycan layerhence retains stain.
pos or neg gram bacteria with thin peptidoglycan layer
neg = thin peptidoglycan layer
differences between pos and neg gram bact
pos = purple stain. thicker peptidoglycan layer. single cytoplasmic membrane attched to peptidoglycan layer via lipoteichoic acid.
neg = pink stain. thinner peptidoglycan layer. double membrane - cytoplasmic and outer memb.
lipopolysaccharide (endotoxin). periplasmic space between outer memb and peptidoglycan layer.
what makes up the lipopolysaccharide layer in gram ___ bacteria
in gram negative bacteria. Lipid A, O antigen and terminal sugars. known as endotoxin - immune response.
3 ways viruses spread genetic variation
transduction - via phages
conjugation - via sex pillus - plasmid transfer
transformation - via plasmids
endotoxins definition
composed of outer membrane of bacteria e.g lipopolysaccharide in gram neg bacteria
exotoxin definition
secreted proteins of gram pos and neg bacteria that cause damage to the host.
