Sporulation Flashcards
Sporulation
- when Bacillus or Clostridium are faced with limiting supplies of C/N, the cells sporulate
- endospores are resistant to heat, UV radiation, desiccation and toxic chemicals
- spores can remain dormant for hundreds of years but will germinate into growing cells when nutrients become available
Endospores and Infectious Disease
- harmless until they germinate
- anthrax
- tetanus
- botulism
- gas gangrene
Endospores as a sterility indicator for autoclaves
- glass ampule w/ media
- after autoclaving flexible vial is squeezed to break and release medium onto spore strip
- yellow medium means spores are viable, autoclaved objects not sterile
- red means spores were killed, autoclaved objects are sterile
Structure of an Endospore-Core
-dehydrated cytoplasm, containing DNA, ribosomes, enzymes and high level of calcium dipicolinate (thought to confer heat resistance properties of the spore)
Structure of an Endospore-Cortex
a modified cell wall/peptidoglycan layer that is not as highly cross linked as in vegetative cell
Structure of an Endospore-Coat
- protein layers that are impermeable to most chemicals
- the coat is responsible for the spores resistance to chemicals
Stages in Sporulation
- Chromosome condenses into axial filament, septum begins to form
- septum is complete and cells divided into 2 compartments-mother cell and forespore
- a copy of the chromosome is translocated into the forespore compartment - mother cell septum grows around the forespore (engulfment)
- the forespore has 2 sets of inner and outer membranes - space between the membranes of the forespore is filled with cortex made of newly synthesized peptidoglycan on the surface of the inner membrane
- A spore coat is laid down around the outer membrane
- the coat is made of proteins synthesized by the mother cell - spore develops resistance properties
- release of mature spore as a result of mother cell lysis
Factors involved in spore septum formation and chromosome partitioning-FtsZ
- Filamentation Temperature Sensitive
- forms a FtsZ ring at both cell poles
- FtsZ ring is formed and septum formation follows
Factors involved in spore septum formation and chromosome partitioning-Spo0A
- the master regulator of sporulation genes
- spo0A- mutant remains at stage 0 of sporulation
- a TF that regulates over 120 genes including those required for chromosomal axial filament and FtsZ ring formation
Factors involved in spore septum formation and chromosome partitioning-SpoIIIE
A DNA translocase that translocates chromosome into the forespore compartment by a mechanism similar to plasmid transfer during conjugation