Lecture 13

Question 1

Bacillus

Answer 1

Gram +
spore formation (8-10 hours)
soil bacteria

Question 2

Spore Formation

Answer 2

• • sensor kinases senses starvation
    1. Assymmetric division; septum
    2. mother cell engulfs forespore with second plasma membrane
    3. Mother adds cortex of peptidoglycan between membranes
    4. coat proteins around forespore
    5. lysis of mother cell
• • sigma factor cascade regulates gene expression

Germination: breaking spores dormant state

Question 3

Anabaena

Answer 3

cyanobacteria
gram -
aquatic
photosynthesis and nitrogen fixation
heterocyst cells and vegetative cells

Question 4

Heterocyst cell

Answer 4

site of nitrogen fixation in Anabaena

devoid of O2

Question 5

Nitrogen Fixation

Answer 5

nitrogenase inactivated by O2
occurs in heterocyst of anabaena

N2 –> Nitrogenase –> NH3 –> Glutamate (nitrogen source) –> vegetative cells

light–> photosystem 1 –> ATP –> nitrogenase

Question 6

Chlamydia

Answer 6

gram -
obligate intracellular bacteria like viruses
chlamydia pneumoniae
chlamydia trachomatis

Question 7

Chlamydia trachomatis

Answer 7

cause #1 STD in U.S.
blindness
treated by azithromycin
dimorphic: elementary body and reticulate body

Question 8

Chlamydia life cycle

Answer 8

1. Elementary body (dormant, infectious) endocytosed into host
2. EB develops into reticulate body
3. RB replicates by binary fission
4. Some RB turn back into EB
5. phagosome and plasma membrane lyse

Question 9

Caulobacter crescentus

Answer 9

Gram -
fresh water and marine bacterium
asym. cell division
dimorphic: motile swarmer cell and non-motile stalked cell

Question 10

Caulobacter crescentus lifecycle

Answer 10

1. Swarmer cell loses flagella
2. development of holdfast
3. replication initiated by development of stalked cell
4. flagella formation on other side
5. cell division: swarmer cell and stalked cell

Swarmer cell cannot replicated DNA until loses flagella
Stalked cell undergoes another round of replication immediately

Question 11

Myxococcus

Answer 11

gram -
soil bacteria
gliding motility: no flagella
myxospores

Question 12

life cyle of myxococcus

Answer 12

1. vegetative cells aggregate under starvation conditions
2. fruiting body forms
   - cell to cell signals
   - coordinated movment: social motility
3. few cells become dormant myxospore