1 - Bacterial properties Flashcards Preview

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Flashcards in 1 - Bacterial properties Deck (10):
1

Which type of bacteria have a thick peptidoglycan layer?

Gram positive

2

Does peptidoglycan retain or lose the gram stain?

retains it
i.e. thicker peptidoglycan= more purple (stained)

3

What colour do gram positive and negative bacteria appear when they are gram stained?

gram positive - deep violet
gram negative - pink

4

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

5

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

6

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

7

How do bacteria replicate?

binary fission (vertical gene transmission)

8

EXAM QUESTION:
Compare the structures of gram positive and gram negative and give examples

GRAM POSITIVE:
- one membrane
- thick layer of peptidoglycan
- retains gram stain - dark violet
- surface proteins
- e.g. Staph. aureus and pneumonia
GRAM NEGATIVE:
- 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

9

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.

10

What are the 3 shapes of bacteria?

BACILLI - rods
COCCI - spheres
SPIRILLI - spirals