week 11 - bacterial differentiation Flashcards
most usual reproduction
binary fission
(asymmetric division producing 2 different daughter cells also possible)
examples:
- endospores and conidia
- heterocyst
structure of the bacterial endospore
- 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
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
- structure
VEGETATIVE: typical gram-positive
ENDOSPORE: thick spore cortex, spore coat, exosporium
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
- calcium content
VEGETATIVE: low
ENDOSPORE: high
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
Dipicolinic acid
VEGETATIVE: absent
ENDOSPORE: present
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
enzyme activity
VEGETATIVE: high
ENDOSPORE: low
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
metabolism
VEGETATIVE: high
ENDOSPORE: low or absent
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
mRNA
VEGETATIVE: present
ENDOSPORE: low or absent
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
radiation resistant
VEGETATIVE: no
ENDOSPORE: yes
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
water content
VEGETATIVE: 80-90%
ENDOSPORE: 10-25% in core
KEY DIFFERENCES BETWEEN VEGETATIVE CELLS AND ENDOSPORES
SASP
VEGETATIVE: absent
ENDOSPORE: present
Bacillus anthracis
- 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
Toxic parasporal crystal in Bacillus thuringiensis
- 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)
Filamentous Actinomycetes:
Streptomyces spp
- 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)
Streptomyces: ecology
- 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
Streptomyces coelicolor life cycle
- Vegetative hyphae emerge from germinating spore
- 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 - 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 - Spore formation
Spore formation in Streptomyces
- 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
Streptomyces: antibiotic production
- 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?
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
organisms
ENDOSPORES: Bacillus
CONIDIA: Streptomyces
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
where formed
ENDOSPORES: within mother cell
CONIDIA: at end of aerial hyphae
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
structure
ENDOSPORES: complex multi-layered
CONIDIA: simple
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
resistant
ENDOSPORES: heat, chemicals, radiation, dehydration
CONIDIA: dehydration
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
metabolism
ENDOSPORES: dormant
CONIDIA: dormant but more active than endospores
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
how formed
ENDOSPORES: spore engulfed by mother cell
CONIDIA: septation of terminal aerial filament
COMPARISON OF ENDOSPORES AND BACTERIA CONIDIA:
role
ENDOSPORES: dispersal and survival in adverse conditions
CONIDIA: dispersal and survival in adverse condition
