Bacterial Cell Structure Flashcards
Major cellular structures
Pili Capsule Flagellum Nucleoid Ribosomes
Capsule
Not required for non-pathogenic lifestyle
Usually made of some combination of polysaccharide, protein, and/or DNA
Function: adherence and immune system avoidance
Biofilms
Organized multicellular bacterial communities
Form when bacteria sense correct density of their cohort (pheromones)
Adherence, immune system avoidance, activation of stress/defense responses, alteration of drug pharmacokinetics
Possibly explains why some antibiotics fail
Flagellum
Organelle used for swimming can be adapted to be a virulence factor (replace the cap for an adhesion molecule, turn flagellum into anchor)
Envelopes
Gram negative: thin peptidoglycan, outer membrane
Gram positive: thick peptidoglycan, no outer membrane
Peptidoglycan
Glycan chains connected by protein cross-bridges
Determines cell shape, stronger than steel
Can be toxic
Degraded by lysozyme (in tears and saliva)
Lipopolysaccharide
Unique to gram negative envelope
Gives it unique properties
Multidrug efflux system
Channel that extends through bacterial envelope, associated with antimicrobial resistance
Endogenous channels but by mutation can become very effective transporters of anti-microbial drugs
Bacterial Spores
Specialized cell type that is dormant and highly resistant
Can be triggered to revive (by presence of nutrients in environment)
Ex: C. diff
C. perfringens
Spores that cause GI disease
Contaminates food, germinate in food to vegetative cells d/t spoilage, toxin is produced with sporulation, toxin causes diarrhea and dispersal of spores results
Mycoplasma
Technically gram positive
Lack peptidoglycans, weird amorphous shapes
Can squeeze through filters and cannot be targeted by drugs, very difficult to kill
