MICR221 Lecture 3 - The 2 Sides of Bacterial Endospores Flashcards
what are endospores mostly formed by?
mostly formed by gram-positive rods in soil
what are the 8 steps of endospore formation?
2 copies of genetic material
septum forms
the septum divides the cell asymmetrically
large compartment engulfs small compartment
forms a forespore
takes up roles to form endospores
the layers mature
an endospore is released into the environment
what are the 7 parts of an endospore structure?
core, inner membrane, germ cell wall (layer 1)
cortex, outer membrane (layer 2)
coat (layer 3)
exosporium (layer 4)
what is layer 1 of an endospore composed of and what does it contain?
composed of the core, inner membrane and germ cell wall that contain normal cell structures that are metabolically inactive - DNA and ribosomes
what is layer 2 of an endospore composed of and what are they made up of?
composed of the core and outer membrane that are layered structures made out of peptidoglycan that is less cross-linked than vegetative cells
what is layer 3 of an endospore composed of and what is it made up of?
composed of the coat that surrounds the cortex and is made up of several impermeable protein layers that provide resistance to chemicals and UV light
what is layer 4 of an endospore composed of and what does it consist of?
composed of the exosporium (final protective shell) and consists of lipids, carbohydrates and proteins
what provides physical resistance for an endospore?
the thick coat layers and the impermeable inner membrane
what provides chemical resistance for an endospore?
provided by the core which has low water content (15% compared to more than 80% in vegetative cells), lower pH and high content of dipicolinic acid and Ca2+
what is the function of the low water content of the core?
the low water content forms a gel-like texture that immobilises inner cell structures
what is the relationship between dipicolinic acid and Ca2+?
the dipicolinic acid forms a lattice structure with the Ca2+ ions which stabilises the DNA
what is the function of small acid soluble proteins in the core?
to bind to DNA and alters its conformation to protect it from damage
what is chemical resistance in the cortex provided by?
provided by decreased peptidoglycan cross-linking (2.9% in endospores compared with 33% in vegetative cells- 10 fold difference between the two)
where does the cross-linking index of endospore cortex peptidoglycan occur?
occurs at only 2.9% of the muramic acid residues because this modified peptidoglycan wall is required for the maintenance of the spore coat dehydration and accompanying metabolic dormancy and heat resistance
what are the 3 stages of endospore germination?
activation (prep for germination)
germination (endospore breaks dormant state)
outgrowth (endospore turns into an active cell that can undergo binary fission)
