Bacterial Endospores L16 Flashcards
what are endospores
dormant structures formed by bacterial cells in unfavourable environments
where are endospores
only in gram positive genera
where are endospores usually found
mostly in bacillus and clostridium
where can endospores also be found that is not common
Can also be formed in less common genera of bacteria
what are the gram negative bacteria (purple)
Escherichia coli
Salmonella typhimurium
Agrobacterium tumefaciens
Campylobacter jejuni
what are the gram positive bacteria
Bacillus anthracis
Clostridium botulinum
Staphylococcus aureus
Listeria monocytogenes
which of the gram positive bacteria that are spore forming
Bacillus anthracis
Clostridium botulinum
who discovered spores
ferdinand cohn
what did ferdinand cohn demonstrate
heat-resistant properties of endospores in Bacillus subtilis
showed the vegetative cells but not the endospores are killed in boiling water
what did ferdinand cohns discovery lead to
development of the autoclave
what do spore forming bacteria aid
identification process
Spore is always in the same place if same cell
restricted to small amount of bacteria – spore forming
Phenomenum in all of them is different
how are endospores formed
intracellularly
what does sporulation start with
asymmetric division of the mother cell
where do spore layers develop
inside mother cell
what happens in sporulation
released from mother cell / sporangium as free spores
what happens in sporulation process
1.asymmetric cell division, spore septum begins to isolate newly replicated DNA and small portion of cytoplasm septum forms at one end of the cell – not cell in half
2. Plasma membrane starts to surround DNA cytoplasm and membrane isolated
End up with a small cell and a big cell – two separate compartments
3. Second engulfment of the spore by the remaining cell
Programmed cell death to form the sporangium
4. Makes peptidoglycan between the two membranes that have formed in the cell
5. DNA degrades, coat forms around peptidoglycan layer, further protection
6. Endospore released
what are endospore composed of
central spore surrounded by various protective layers exosporium spore coat cortex core
what is the exosporium
thin covering made of protein
what is spore coat
highly cross-linked keratin and layers of spore specific proteins
what is the cortex
loosely cross-linked peptidoglycan
what is the core
condensed chromosome, packaging proteins and spore-specific compounds
if there is severe dehydration what happens
no processes can occur
what are bacterial endospores known for
most heat resistant living structures
what are bacterial endospores resistant to
Pressure Vaccum Desiccation Irradiation (UV, X- and γ- rays) Antibiotics Chemical disinfectants Extremes of pH Heat
what are the reasons for spore stability
Proteinaceous Coat Calcium dipicolinate Specialized DNA-binding proteins Dehydration of the cortex DNA repair enzymes in the endospore
what is the proteinaceous coat function in spore stability
resists lysozyme /degradative enzymes; impermeability of this layer protects spore from chemical inactivation
what is the calcium dipicolinate function in spore stability
stabilises DNA
what is specialised DNA-binding proteins function in spore stability
coats DNA and protects from heat, drying, chemicals, UV radiation
what is dehydration of cortex function in spore stability
removes water from endospore interior and prevents diffusion
what is the DNA repair enzymes in endospore function in spore stability
repair damaged DNA during germination
what can spores used for
some spores contain spore associated toxins
clostridium botulinum causes botulism - for botox, causes paralysis of muscles
what can spores cause in humans
Bacillus cereus & Clostridium perfringens cause food poisoning (GI tract)*
what is bacillus thuringiensis protein specific for
Lepidoptera
what must the conditions be for bacillus thuringiensis be to be solubilised
only solubilised under alkaline conditions (in gut of insect larvae) activated in alkali (insect gut pH is alkali)
what is bacillus thuringiensis purified toxin known as
organic pesticide
how can purified toxin be made
can purify the toxin then use that
Or can spray around bacillus thuringeiensis the organism that makes the toxin (natural so preferred)
what is the downside of the natural method to produce purified toxin
closely related to bacillus cereus which will do that to us to harmful
how can endospores enter the body
abrasions to skin orin lungs
what happens when spores enter the body
favourable conditions allow the spores germinate and new vegetative cells start to grow
what is a bacterial endospore
a neurotoxin
what causes sporulation
Entry into the sporulation cycle can only occur at a specific point in the cell cycle
Requires active cell division
dont want togo into sporulation unless have to
what things lead to sporulation
nutritional signals
population density
how do nutritional signals lead to sporulation
Carbon, Nitrogen or Phosphorous starvation induce sporulation
Rapidly metabolised carbon sources, (e.g. glucose) repress sporulation
how does population density lead to sporulation
Sporulation not induced efficiently at a low population density
At high density vegetative cells grown produce a substance necessary for efficient sporulation
what do some endospores need before germination
activation
how are most endospores activated
heat - required for optimum germination but amount of heat varies with spore type
or chemical signal - some simple chemical act as signals
what is a downside of sporulation
very energy costly - Cells don’t induce this unless appropriate environmental signals present
what is an advantage of endospores
can persist for a long time in inert state
what is a disadvantage of germination
not guaranteed - dependent on environmental signals
