week 11 - bacterial differentiation

Question 1

most usual reproduction

Answer 1

binary fission

(asymmetric division producing 2 different daughter cells also possible)

examples:
- endospores and conidia
- heterocyst

Question 2

structure of the bacterial endospore

Answer 2

• Structurally complex – many layers
• Contains dipicolinic acid complexed with Ca2+
  o Dehydrates endospores and stabilises DNA
   DNA in water more likely to react chemically
   Or react with UV
• Core contains small-acid soluble proteins (SASP)
  o Bind DNA – protection from damage
   Intercalate -> no specific binding, get into DNA helical structure
  o Carbon and energy source for germination

Question 3

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
- structure

Answer 3

VEGETATIVE: typical gram-positive

ENDOSPORE: thick spore cortex, spore coat, exosporium

Question 4

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
- calcium content

Answer 4

VEGETATIVE: low

ENDOSPORE: high

Question 5

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
Dipicolinic acid

Answer 5

VEGETATIVE: absent

ENDOSPORE: present

Question 6

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
enzyme activity

Answer 6

VEGETATIVE: high

ENDOSPORE: low

Question 7

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
metabolism

Answer 7

VEGETATIVE: high

ENDOSPORE: low or absent

Question 8

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
mRNA

Answer 8

VEGETATIVE: present

ENDOSPORE: low or absent

Question 9

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
radiation resistant

Answer 9

VEGETATIVE: no

ENDOSPORE: yes

Question 10

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
water content

Answer 10

VEGETATIVE: 80-90%

ENDOSPORE: 10-25% in core

Question 11

KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
SASP

Answer 11

VEGETATIVE: absent

ENDOSPORE: present

Question 12

Bacillus anthracis

Answer 12

• Causes antharax
• > 80% mortality when untreated
  o Can be treated successfully with antibiotics
  o But often damage too severe before realise
• Grows in lymph nodes and lymphatic tissue of lungs
• Death from septicaemia, haemorrhagic (infection of layers around the brain) meningitis
• Spores are long lasting and easy to disperse
  o Potential bio-weapon

Question 13

Toxic parasporal crystal in Bacillus thuringiensis

Answer 13

• Parasopral body
  o Crystalline structure
• BT toxin: toxic to insect larvae
  o Activated in their guts
• Insect resistant GM crops
  o Have the genes encoding the toxin (not the bacillus)

Question 14

Filamentous Actinomycetes:
Streptomyces spp

Answer 14

• Filamentous, Gram positive bacteria
• Branching filaments
  o Produce mycelium analogous to mycelium of filamentous fungi
• Produce spores called conidia
• Important secondary metabolites
• Strict aerobes that produce many extracellular enzymes
  o Genomes are typically quite large (8 Mbp and larger)

Question 15

Streptomyces: ecology

Answer 15

• Primarily soil microorganisms
  o Over 500 species of Streptomyces are recognized
• Abundant and important in soil
  o Major role in the cycling of carbon trapped in insoluble organic debris
  o Produce many and diverse hydrolytic exoenxymes
   Enzymes that can break down difficult things to break down
  o 7 cellulases and 5 chitinases

Question 16

Streptomyces coelicolor life cycle

Answer 16

1. Vegetative hyphae emerge from germinating spore
2. Mycelial growth
   - Tip extension gives filaments
   - Few cell walls, many copies of the genome in each “cell”
   - Elongate and branch on the surface and penetrating the medium
3. Nutrient depletion results in a switch to growth of aerial hyphae
   - Complex signalling cascade
   - Production of a surfactant coats emerging filaments allows them to grow away from the substrate
   - Substrate mycelia used as nutrient source
4. Spore formation

Question 17

Spore formation in Streptomyces

Answer 17

• Spores produced when colony ages
• Aerial hyphae formed
  o Many copies of genome
• Growth stops
• Cross walls formed
  o Synchrous, multiple septation
  o Gives rise to prespore compartments
  o One copy of genome
• Mature and develop characteristic grey pigment
• Spores are for survival and dispersal

Question 18

Streptomyces: antibiotic production

Answer 18

• Antibiotic production
  o Secondary metabolites
  o 50% of all isolated Streptomyces produce antibiotics
  o Over 500 distinct antibiotics produced by Streptomyces
  o ~50 with human, veterinary or industrial applications
   E.g. Aminoglycosides, Tetracyclines
  o Production linked to sporulation
  o Survival strategy?

Question 19

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
organisms

Answer 19

ENDOSPORES: Bacillus

CONIDIA: Streptomyces

Question 20

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
where formed

Answer 20

ENDOSPORES: within mother cell

CONIDIA: at end of aerial hyphae

Question 21

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
structure

Answer 21

ENDOSPORES: complex multi-layered

CONIDIA: simple

Question 22

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
resistant

Answer 22

ENDOSPORES: heat, chemicals, radiation, dehydration

CONIDIA: dehydration

Question 23

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
metabolism

Answer 23

ENDOSPORES: dormant

CONIDIA: dormant but more active than endospores

Question 24

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
how formed

Answer 24

ENDOSPORES: spore engulfed by mother cell

CONIDIA: septation of terminal aerial filament

Question 25

COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
role

Answer 25

ENDOSPORES: dispersal and survival in adverse conditions

CONIDIA: dispersal and survival in adverse condition