Bacteria Flashcards
Name the different shapes of bacteria.
Coccus = sphere
Bacillus = rod
Coccobacillus
Pleomorphic = different shapes
What is the structure of a bacterium?
Nucleoid (no membrane-bound nucleus), ribosomes, inclusion bodies, mesosome (folding of membrane), capsule -> cell wall -> plasma membrane, surface proteins, flagellum
Describe the Gram positive cell wall.
Peptidoglycan layer, stabilised by lipoteichoic and teichoic acids. Forms a barrier to keep water in.
Describe the Gram negative cell wall.
Layer of peptidoglycan between two plasma membranes, lipopolysaccharide layer outside. O antigen allows repulsion of host’s immune cells.
How is a Gram stain carried out, and what purpose does it have?
Heat fixed smear -> crystal violet -> iodine -> alcohol -> dilute fuchsin
Distinguishes between Gram positive and Gram negative
What are the different types of plasmid?
R = resistance V = virulence Col = colicin F = fertility D = degradative
What are the two types of variation that occur and what effect do they have?
Mutation = affect resident genome
Recombination = rely on new DNA
What can variation affect?
- Virulence
- Resistance to host defences
- Resistance to treatments
What is the difference between a saprophyte and a parasite?
Saprophytes = free-living, parasites = in/on animals
What are the three types of parasitic bacteria?
Symbiotic = bacteria and host benefit
Commensal = bacteria benefit but cause no harm
Pathogenic = bacteria benefit and cause harm (obligate vs facultative (opportunistic) pathogens)
What is the difference between exogenous and endogenous infection?
Exogenous = from the environment / other hosts
Endogenous = from animal’s own commensal flora
List the opportunities for facultative pathogens.
New body site: harmless commensal flora introduced into a different body cavity
Altered body site: temperature / pH / commensal flora (antibiotics, rapid nutritional change)
Reduced defenses: age, malnutrition, immunosuppressed, stress
