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Lecture 9

BIOL 2P98 Lecture Notes - Lecture 9: Nucleoid, Mine, Ftsz


Department
Biological Sciences
Course Code
BIOL 2P98
Professor
Mac Neil Lori
Lecture
9

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Microbiology Lecture # 9 September 28th 2015
Endospore structure
oOutermost layer is thin protein covering called the exosporium
oMoving inward are several spore coats consisting of layers of spore-
speci%c proteins
oCortex is peptidoglycan that is less cross-linked than normal wall
oCore consists of cytoplasmic membrane, cytoplasm, nucleoid,
ribosomes & other cellular essentials surrounded by a core wall
(peptidoglycan)
Why so resistant?
oCoat protects from chemicals and exogenous enzymes
oCore contains high levels of dipicolinic acid and calcium (Ca2+)
oComplex together and bind free water, dehydrating the core
oInsert between DNA bases & help stabilize it
oDehydration of the core:
oIncreases resistance to heat and toxic chemicals
oProtect the cell
oContain less that ¼ of the water you would %nd in a non-vegetative cell
oRenders enzymes inactive but does not denature them
oAcid not found in vegetative cell
oOnly found in the endospore
oHigh levels of small acid-soluble spore proteins (SASPs)
oCombines with calcium; with the 2 components it helps hydrate the cell
oBind tightly to DNA & protect from damage
oFunction as a carbon and energy source during germination
Reactivation
Occurs in three stages:
1. Activation
Prepares spore for germination
Often results from heating
2. Germination
Environmental nutrients are detected
Water uptake and breakdown of cortex
Cortex: Layer of peptidoglycan
Increased metabolic activity
3. Outgrowth
Exit spore coat & return to vegetative state
Chapter 5: Microbial Growth and Control
Bacterial cell division
Growth: increase in the number of cells
Binary %ssion: cell division following enlargement of a cell to twice its
minimum size

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Microbiology Lecture # 9 September 28th 2015
Partition that constricts the cell into two daughter cells = septum
Each daughter cell receives a chromosome and su@cient copies of all
other cell constituents to exist as an independent cell
Generation time: time required for a cell population to double in
number
DNA replication & Cell division
Most bacterial chromosomes are circular
oContain a single origin of replication
oReplication starts on one site
oDNA replication begins at the origin and proceeds in both
directions
= Bidirectional
Fts (%lamentous temperature-sensitive) proteins are
essential for cell division in all prokaryotes
oInteract & form a division apparatus called the divisome
Form at that part of the cell that elongated
Helps divide the big cell into 2
oFtsZ proteins polymerize to form a ring at the cell-division plane
Form chain of FtsZ proteins
Form ring at centre
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