Lecture 2 & 3: Bacteria Flashcards
1
Q
Distinguishing characteristics of Bacteria (prokaryote)
A
- Cell wall: present except for mycoplasma
- Cytoplasmic membrane: no sterols except mycoplasma
- nuclear membrane: absent
- nucleolus: absent
- Hereditary info: ssDNA w/ no proteins associated
- Ribosomes: small 70s
- respiration: associated particles in cytoplasmic membrane
- repro: asexual (binary fission)
2
Q
Congenital infections
A
- Sexual disease: T. Pallidum
- GI disease: L. monocytogenes
- viral causes: rubella
3
Q
Exogenous sources of microbial disease
A
Ingress
- Inhalation: common cold (viruses), coccidioidomycosis (fungus)
- Ingestion: dysentry (bacterium)
Penetration
- Wound: surgical infections & cat scratch (bacteria)
- insect bites: encephalitis (virus)
4
Q
Cell arrangement: Coccoidal
A
- pairs: diploccoci (Strep. pneumoniae)
- chains: streptococci (Strep. pyogenes)
- clusters: staphylococci (all staphylococcus sp.)
- tetrads: Sarcina sp.
5
Q
Types of stains
A
- Gram-stain (stain -> decolourizer -> counterstain)
- Acid Fast stain:
- for Gram’s resistant bacteria ex. mycobacterium & Nocardia spp.
- Ziehl-Neelsen (hot), Kinyoun (cold), fluorochrome (auramine-rhodamine; primary stain: fluorescent dyes; counterstain: potassium permanganate)
6
Q
Flagellum arrangement
A
Polar
- monotrichous: Ex. Vibrio sp.
- Amphitrichous: Ex. Spirillum sp.
- Lophotrichous: Ex. Pseudomonas sp.
Lateral
- Peritrichous: Ex. Proteus sp.
7
Q
Cell envelope components
A
- Glycocalyx (aka capsule, slime (s-) layer
- External mucilaginous layer (EPS) Ex. Bacillus anthracis (polypeptide)
- slime layer: poor organisation
- capsule: organised, K antigen (Exceptions: M - S. pyogenes, Vi -Salmonellae)
- Fx: adherence, antigenic activity, antiphagocytic, prevention of neutrophil killing of engulfed bacteria, prevention of PMN leukocyte migration to site of infection, toxicity to host cells, protection - Cell wall - Peptidoglycan backbone - alternating polysaccharide chains alternating NAM & NAG
- Gram +ve: thick peptidoglycan; Teichoic acids (Fx: bind protons, cations, act as adhesins, virus receptor sites); Lipoteichoic acid (dermal necrosis/Schwartzman rxn, induction of cell mitosis at site of infection, immune system stimulation, complement activation)
- Gram -ve: thin peptidoglycan; LPS; porins (nutrient transport)
8
Q
Endotoxin induction of:
A
- fever
- haemorrhagic necrosis (Schwartzman rxn)
- disseminated iv coagulation
- production of TNF
- activation of alternate complement pathway
- stimulation of bone marrow cell proliferation
- enhancement of the immune and limulus lysate rxn
9
Q
Acid-Fast Bacteria
A
- Genera Mycobacterium & Nocardia
- Peptidoglycan + arabinose & galactose polymers -> mycolic acids (waxy)
10
Q
Effect of lysozyme
A
- breaks Beta1-4 bonds b/w NAM & NAG
- spheroplast: portion of cell wall remains because lysozyme only enters in portion of cell wall with porins
- protoplast: cell wall completely removed (Gram +ve more sensitive) due to lack of 2nd layer of cell wall
11
Q
Effect of penicillin
A
- prevents cell wall formation only in growing cells (no effect on Mycoplasma)
- inhibits formation of nl cross-linkages in peptidoglycan
- binds irreversibly to penicillin-binding proteins (PBP transpeptidases)
- result: defective cell walls
- no protection from osmotic shock
12
Q
Periplasmic space contains:
A
- nutrient transport proteins
- nutrient acquisition enzymes (proteases)
- detox enzymes (Beta-lactamases)
- membrane Derived Oligosaccharides (MDO)
- Osmoprotectants
13
Q
Pathogenicity Islands (PAI)
A
Distinct genetic elements on chromosome:
- virulence genes
- present only in pathogen genome
- occupy large genomic areas (10-200 kb)
- differ from core genome (base composition & operon useage)
- frequently located next to tRNA genes
- frequently associated with mobile genetics elements (transposons)
14
Q
Ex. of pathogens with PAI
A
Grav +ve
- Listeria spp.
- S. aureus
- Streptococcus spp.
- Enterococcus faecalis
- C. diff
Gram -ve
- H. pylori
- E. coli
- Salmonella spp.
- Shigella
- Yersinia spp.
- L. pneumophilia
- P. auruginosa
- V. cholerae
- Bacteroides fragilis
15
Q
Endospores
A
- 2 bacterial genus produce spores: Botulinum and Bacillus
- Specialised structures: produced in env. stress for spore to survive harsh conditions
- Resistant: UV, irradiation, chemical disinfection, drying
- require specialised stains (light microscopy)
- Coat: keratin-like, impermeable layer (resistance to antibacterials)
- Cortex: type of peptidoglycan (fewer cross-links)
- Spore wall: peptidoglycan layer; cell wall germinating vegetative cell
- Core: contains complete genetic material
