Flashcards in 1 - Bacterial properties Deck (10):
Which type of bacteria have a thick peptidoglycan layer?
Does peptidoglycan retain or lose the gram stain?
i.e. thicker peptidoglycan= more purple (stained)
What colour do gram positive and negative bacteria appear when they are gram stained?
gram positive - deep violet
gram negative - pink
Following the gram stain, what can be done to identify the bacteria?
- culture and microscopy
- biochemical and serological tests
- DNA techniques such as PCR
- sensitivities to antibiotics is determined
How does salmonella invade a cell?
- polymerise the actin into filaments
- this ruffles the plasma membrane and bacteria get stuck in the ruffle
- as the process dies down and returns to normal, the trapped bacteria is internalised
What is the structure of the flagella and how they propel bacteria through fluids?
filamentous structures that are organised as a series of rods and filaments that rotate to allow propulsion
How do bacteria replicate?
binary fission (vertical gene transmission)
Compare the structures of gram positive and gram negative and give examples
- one membrane
- thick layer of peptidoglycan
- retains gram stain - dark violet
- surface proteins
- e.g. Staph. aureus and pneumonia
- 2 membranes (inner + outer)
- thin layer of peptidoglycan
- doesn't retain gram stain swell - pink
- LPS on surface (a PAMP)
- e.g. E.coli, salmonella, shigella
What are acid-fast bacteria?
give some examples
- have lipid-rich cell walls (due to containing mycolic acid).
- they are resistant to penetration by chemical dyes such as those used in the Gram stain.
- other tests such as the Ziehl-Neelsen are performed instead to identify the bacteria in these cases.
- e.g. Mycobacterium tuberculosis, which causes TB.