Facultative structures Flashcards
What structures can bacteria contain for specific metabolic functions?
Carboxysomes - Photosynthesis dark reactions.
Pigments/Chromatophores
What facultative structures are in bacteria for survival/protection/defence?
Polysaccharide capsule
Plasmids
Storage granules
SPORES
What facultative structures of bacteria serve for motility?
Flagella
PILI
Gas vacuoles
What are endospores?
Resistant, tough NON-REPRODUCTIVE structure.
Produced mostly by Gram +ve bacteria.
Structure differentiated from vegetative cells.
Which are resistant to severe conditions and can be identified by their position in the mother cell…
How can endospores be identified?
Do not show in Gram Staining:
Instead, using Witz staining:
Using heat and malachite green, counter stained with Fusein.
What is the general structure of endospores?
A facultative, loose Exosporium surrounds the endospore.
TUNIC = A thick, waterproof, layers of protein.
= RESISTANCE
Cortex - can occupy 50+% of spore volume.
= Contains a peptidoglycan, and surrounds classical structures like PM, ribosomes, nucleoid.
A dehydrated Core = Cytoplasm.
= MORE RESISTANT TO HEAT>
What substances are found in Endospores?
The core = dehydrated cytoplasm
= In order to provide heat resistance and avoid boiling water in cytoplasm.
(only 20% water, vs 80% elsewhere and normally)
Cytoplasm has high Ca2+ conc. which is contained by dipicolinic acid = heat resistance.
Small-Acido soluble proteins (SASPs) protect DNA against heat.
How does the endospore form?
Hostile conditions, promote the start of sporulation cycle
(Forming endospores)…
= Exiting the vegetative cycle.
First, there is chromosomal duplication and assymetric cell division.
= Forming the forespore.
The mother cell engulfs the Forespore - with formation of the different surrounding layers e.g. Tunica, Cortex, Exosporium.
When Endospore has matured, the mother cell will undergo lysis and release the endospore.
After dormancy, favorable conditions will promote germination of spore.
How does the endospore germinate
In favorable conditions, the dormant endospore will start germination.
= To emerge as a vegative cell and recommence vegeative growth.
1
Activation = Tunica of spore lyses by environmental factor like shock, heat, acidity…
- The cortex is removed and the the core is hydrated… IF IN FAVORABLE CONDITIONS… nutrients like AAs, Mg2+, adenosine.
3
Growth - biosynthesis activated.
How can endospore be destroyed?
Tyndallization - process of spore removal.
Discontinous heating at low temp, then short burst of hot for 30 mins every day… Over 3 days.
Encouraging spore germination at lower temp, but vegetative cells die off in heat.
What is difference between chemotactism and motility?
Motility is ability of some bacteria to make own movements.
Chemotaxis - is movement in response to attractants/repulsants.
What are the different forms of motility?
Swimming - requires flagella
Gliding - secrete polysach.
Social gliding - traction by Type 4 pili.
Vertical - Gas vacuoles.
Magnetic - Magnetosomes.
Do archaeea have flagella?
Archeae can have flagella
Thinner than bacterial flagella (10-12nm diameter).
Similar to Type 4 pilus.
A full extracellular organite.
Rotation is not powered by PMF, but ATP hydrolysis.
What are the different secretion systems?
Flagella are modified Type III secretion systems.
T3 secrete adherence proteins.
Salmonella have T3 secretion systems to inject virulence factors into host cells.
Type 4 secretion systems secrete proteins/nucleoprotein complexes.
How do spirochete flagella differ from other bacterial flagella?
Bacterial flagella are anchored to cytoskeleton, so originate from cytoplasm. In Spirochetes, flagella can be periplasmic = enable viscous environment motility.
