1. Bacterial properties

Question 1

Bacterial Forms

Answer 1

Cocci: Oval-shaped/ spherical
Bacilli: Rod shaped
Spirilli: Curved (gentle curve- corkscrew-like spiral)

Question 2

Gram stain

Answer 2

Distinguishes between 2 different kinds of bacterial cell walls
Bacteria stained with a violet dye and iodine, rinsed in alcohol, then stained with a red dye.

Question 3

Gram positive bacteria

Answer 3

Peptidoglycan in cell wall retains dye.

High peptidoglycan = deep violet

Question 4

List 2 Examples of Gram+ bacteria

Answer 4

Staphylococcus aureus

Streptococcus pneumoniae

Question 5

Gram negative bacteria

Answer 5

Dye is lost from thinner peptidoglcan
Have 2 membranes (more difficult to get antibiotics through)
The cells absorb counterstain making them appear pink

Question 6

List 3 Examples of Gram- bacteria

Answer 6

Escherichia coli
Salmonella
Shigella

Question 7

Mycobacteria

Answer 7

Have characteristics of both Gram+ and Gram-

Question 8

How to identify Mycobacteria

Answer 8

Stain red with Kinyoun stain

Question 9

Mycobacteria are acid fast

Answer 9

Have a high content of mycolic acids in the cell walls

Question 10

List 4 Extracellular pathogens

Answer 10

Staphylococcus
Streptococcus
Yersinia
Neisseria

Question 11

Infectivity

Answer 11

Organisms ability to infect

Question 12

Virulence

Answer 12

Measure of the degree of disease that a pathogen causes

Question 13

Infective dose

Answer 13

Amount of a pathogenic agent that will cause infections in susceptible subjects

Question 14

Salmonella uses which 2 evolutionary related protein machines?

Answer 14

Flagellum (movement)

Injectisome (causes actin polymerisation, membrane ruffling, bacterial internalisation)

Question 15

Mode of replication in bacteria

Answer 15

Binary fission

Question 16

Gene repertoire

Answer 16

Genomes of bacterial pathogens encode 500-4500 proteins:
Core genes (40%)
+
Accessory genes (vary between different strains)

Question 17

Vast majority of accessory genes acquired by…

Answer 17

Horizontal Gene Transfer

Question 18

HGT- Transformation

Answer 18

DNA uptake and integration by homologous recombination

e.g. Neisseria

Question 19

HGT- Conjugation

Answer 19

Physical bridge between bacteria allows the transfer of a plasmid between the bacteria
Many Gram+ and Gram-

Question 20

HGT- Phage Transduction

Answer 20

Phages infect bacteria and replicate their DNA
Cuts bacterial DNA into small pieces
Some bacterial DNA may be packaged into the phage heads
New phage particles are released, these inject bacterial DNA from the previous bacterium into the next bacterium.
Injected DNA may be incorporated into the bacterial chromosome.
Many Gram+ and Gram-

Question 21

3 Modes of HGT

Answer 21

Transformation
Conjugation
Phage Transduction

Question 22

Pathogenicity Island

Answer 22

Horizontally Acquired DNA that contributed to Virulence

Question 23

List 6 examples of Intracellular pathogens

Answer 23

Salmonella
Mycobacteria
Chlamydia 
Listeria
Shigella
Coxiella