foundation microbiology

Question 0

explain the nucleoid of bacteria

Answer 0

• no nuclear membrane
• mostly DNA
• single, circular closed dsDNA looped and supercoiled
• no introns or exons
• “core” and “accessory” genome for each species
• can acquire genes horizontally

Question 1

what are the key components of bacteria

Answer 1

• cytoplasmic membrane
• matrix
• ribosomes
• genome
• cell wall

Question 2

what colour are gram positive and negative bacteria

Answer 2

positive - blue

negative - pink

Question 4

what makes a bacteria gram positive

Answer 4

thick layer of peptidoglycan

- also contains teichoic acids (only found in Gram +ve)

Question 5

explain the structure of peptidoglycan

Answer 5

disaccharide backbone - N-acetyl glucosamine (G) alternating with N-acetyl muramic acid (M) with its peptide chain
- linked together by pentapeptide bridge

Question 6

what makes a bacteria gram negative

Answer 6

• outer membrane with lipopolysacchardies

- only thin layer of peptidoglycan

Question 7

what is the major advantage of being a gram negative bacteria

Answer 7

the outer membrane prevents entry of bile salts, and some antibiotics

Question 8

what is the significance of the LPS in gram negative bacteria

Answer 8

acts as an endotoxin (PAMP) - potent stimulator of innate immune system

Question 9

explain the structure of the layers of a gram negative wall

Answer 9

from inner to outer:

• plasma membrane
• periplasmic SPACE with peptidoglycan
• outer membrane with LPS

Question 10

explain the structure of LPS

Answer 10

• lipid head
• core polysacchardie
• chains of repeating peptide (O-ANTIGEN)

Question 11

explain the wall of an Acid fast bacteria

Answer 11

• has peptidoglycan base layer

- then additional layers of arabinogalactan, mycolic acid and lipid

Question 12

what is the advantage of having an acid-fast wall

Answer 12

confers resistance to drying and many harsh chemicals and antibiotics

Question 13

what is the disadvantage of having an acid-fast wall

Answer 13

slow rate of nutrient uptake = slow growth

Question 14

function of flagella

Answer 14

motility

Question 15

how do we serotype E coli

Answer 15

using their O and H antigens
O antigen - LPS
H antigen - on flagellum

Question 16

function of pili (fimbriae)

Answer 16

attachment to other cells and each other

- sex pili involved in the transfer of plasmids between bacteria

Question 17

where are pili found

Answer 17

• on most gram -ve and only some gram +ve

Question 18

what is a bacterial capsule made of

Answer 18

polysacchardie

Question 19

functions of bacterial capsules

Answer 19

• protection against dehydration
• contribute to its virulence
• protects against phagocytosis

Question 20

spores are resistant to what

Answer 20

• heat
• desiccation
• UV
• many chemicals

Question 21

bacteria replicate by..

Answer 21

binary fission

Question 22

what are the 3 phases of the bacterial growth curve

Answer 22

• lag phase - getting used to the environment
• exponential phase - exponential growth
• stationary phase - used up the nutrients and growth slows down

Question 23

what is a facultative anaerobe

Answer 23

grows with or without air

Question 24

what is an aerotolerant anaerobe

Answer 24

survives in oxygen (not killed, but cannot grow)

Question 25

what is a microaerophile

Answer 25

grows best in low concs of oxygen

Question 26

what are the current techniques used to identify medically important bacteria (8)

Answer 26

- microscopy - culture - proteomics - genomics - detection of structural antigens - susceptibility to bacteriophages and bacteriocins - production of toxins and other virulence determinants - pathogenicity for animals

Question 27

what are the 4 major components of viruses

Answer 27

genome matrix capsule envelope

Question 28

how does a virus acquire an envelope

Answer 28

acquired from budding from the host cell

Question 29

what is a viral capusle

Answer 29

a protein shell

Question 30

what are the two major structures of viral capsids

Answer 30

icosahedral | helical (associated with envelope for support)

Question 31

which virus does not have a helical or icosahedral capsule

Answer 31

poxvirus - has complex symmetry

Question 32

what is the function of a viral capsule

Answer 32

protects from breakdown by nucleases

Question 33

which virus has multiple capsules

Answer 33

rotavirus - makes it very hardy

Question 34

all helical viruses are DNA or RNA

Answer 34

RNA

Question 35

all RNA viruses have ...

Answer 35

an envelope

Question 36

what are the methods of viral detection

Answer 36

- direct visualisation by electron microscopy - viral gene detection - host serological responses - viral antigen detection - viral cultivation (gold standard)

Question 37

what is the virus that caused SARS

Answer 37

coronavirus

Question 38

where did the virus come from that caused SARS

Answer 38

civil cats

Question 39

what is a virus

Answer 39

subcellular genetic elements that are obligate parasites

Question 40

what is a viral envelope composed of

Answer 40

lipid with glycoproteins embedded

Question 41

what are the 3 steps to make a specific diagnosis of infection

Answer 41

1. demonstrate organism, compound or product 2. isolate organism 3. demonstrate a serological response

Question 42

what are the 4 techniques in which you can demonstrate an organism

Answer 42

- microscopy - antigen detection - nucleic acid detection - mass spec

Question 43

what techniques are used for antigen detection

Answer 43

- latex agglutination - solid phase assay - capture assay

Question 44

explain how latex agglutination works

Answer 44

- antigen is in solution - latex particles are coated with known antibody - cross linking of the latex particles when antibody bound to antigen = agglutination

Question 45

explain how solid phase assay works

Answer 45

- antigen in solid phase | - known labelled Ab binds and gives result

Question 46

explain how capture assay works

Answer 46

- 1st Ab on the solid phase - antigen introduced and binds - 2nd antigen (labelled) introduced and binds to antigen --> result

Question 47

what are the two types of nucleic acid detection

Answer 47

hybridisation | PCR

Question 48

what are the 4 ways you can demonstrate a serological response to an organism

Answer 48

- Tube agglutination test - solid phase assay - Western blot - rising titre/specific IgM

Question 49

for bacteria to cause infection of mucosal surfaces.. what does it have to do

Answer 49

- overcome competition by commensals - move through mucus - resist mucosal defences - adhere to epithelial cells

Question 50

what are the attributes of a bacterial pathogen

Answer 50

- adhesion - colonisation - penetration - multiplication - tissue damage

Question 51

how do bacteria penetrate epithelial cells

Answer 51

via pathogen-mediated endocytosis

Question 52

what two things must bacteria do to evade immune system removal

Answer 52

- evade phagocytosis (EC) | - resist killing (IC)

Question 53

how can bacteria evade phagocytosis

Answer 53

``` direct effects on phagocytes - production of leukocidins - anti inflammatory toxins and enzymes - surface anti-phagocytic structures interfering with opsonins - C' - Ab ```

Question 54

how can bacteria resist IC killing

Answer 54

- inhibit respiratory burst - prevent phagolysosome formation - escape from the phagocytic vacuole - resist bactericidal systems

Question 55

how do capsules enhance virulence

Answer 55

- electrostatic repulsion - resemble host components - mask underlying structures - -> unable to be opsonized by C' - -> can be opsonized by Ab

Question 56

what techniques do bacteria have to evade adaptive immunity

Answer 56

- direct immunosupression - expression of weak antigens - antigenic diversity - antigen modification

Question 57

which bacteria modifies its antigen to evade the immune system

Answer 57

salmonella