Bacterial properties Flashcards
What is the difference between Gram-negative and Gram-positive bacteria?
Gram Positive:
- only ONE membrane
-This is a Thick layer of peptidoglycan, which retains the dye giving it a DEEP violet
Gram Negative:
-2 membranes
-peptidoglycan is sandwiched between the inner and outer membrane
-outer membrane is composed of Lipopolysaccharide (LPS)
- thinner peptidyglycon
-colour pink
Give examples of some Gram-negative pathogenic bacteria and the diseases they cause.
E. coli – diarrhoea, dysentery, kidney failure
Salmonella - food poisoning, typhoid
Shigella – dysentery
Neisseria – meningitis + gonorrhoea
Vibrio cholerae - cholera
What feature is found only on Gram-negative cell walls?
Lipopolysaccharide
Give examples of some Gram-positive pathogenic bacteria and the diseases they cause.
Staphylococcus aureus – skin infections, endocarditis, bacteraemia, joint disease, pneumonia
Streptococcus pneumoniae – pneumonia, meningitis, otitis media
Streptococcus pyogenes – tonsillitis, necrotising fasciitis, scarlet fever, bacteremia
Give examples of some Mycobaceria and the diseases they cause
Mycobacterium tuberculosis – TB Mycobacterium leprae - leprosy
What is another way of classifying bacteria?
Intracellular and Extracellular pathogens
Give examples of some extracellular pathogens.
- Staphylococcus
- Streptococcus
- Neisseria
- Yersinia
What are the three methods by which bacteria survive in the host cell?
Escape (break down the vesicle and escape into the cytoplasm)
Preventing fusion with lysosome.
Surviving in the phagolysosome (harsh environment)
Give examples of bacteria that survive using each of the above methods.
Escape – Listeria, Shigella Prevent fusion of lysosome – Salmonella, Mycobacteria, Chlamydia (obligate)
Survive in phagolysosome - Coxiella
What does the salmonella surface structures enable?
Motility and invasion:
- these polymerise actin into filaments
- this ruffles the plasma membrane and bacteria get stuck in this ruffle
- as the process dies down, trapped bacteria is internalised
Motility and Invasion require which two multi-protein machines and what do they do?
Flagella: allow the propulsion of bacteria through fluids- they are filamentous structures and they rotate and are organised as a series of rods and filaments.
Type III Secretion system: delivers virulence( ability of a pathogens ability infect host cells) proteins into the host cell.
What does bacterial virulence do?
Bacterial virulence proteins (effectors) induce actin polymerisation, membrane ruffling and bacterial internalisation.
injectisome (transfer of virulence proteins into host cells)
Describe the role of the type III secretion system.
What bacteria can do this?
instead of making a flagellum, a bacterium can make this needle shaped structure, which allows effector protein to be injected into the host cell through translocase.
- the translocan inserts into the plasma membrane of host cell
- effector protein leads to actin polymerisation, which causes the uptake of bacteria into the host cell.
Salmonella uses evolutionary related protein machines:
flagellum (movement)
injectisome (causes actin polymerisation, membrane ruffling, bacterial internalisation)
Salmonella
What type of bacteria have this feature?
Many negative bacteria but NO GRAM positive bacteria have this.
Describe another way in which actin is manipulated by bacteria.
What bacteria can do this?
- it breaks out of the vacuole
- it then assembles actin at one pole of the bacterial cell forming comet tails
- this polymerisation of actin generates force which propels the bacterium through the cytoplasm
Listeria and shigella
