nester03b
TRANSCRIPT
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Chapter 3:
Microscopy and
Cell Structure
http://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htm -
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Important Point:
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Typical Bacterial Shapes
Also Pleomorphic Bacteria, which vary in their shape(e.g., Corynebacterium).
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Typical Bacterial Arrangements
streptococci
sarcina
staphylococci
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Prokaryotic
Cell Structures
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Typical Prokaryotic Cell
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CytoplasmicMembrane
Movement across membrane for many substances
is controlled by membrane proteins.
Escherichia colihas >200 membrane proteins.
Many of these proteins are involved in transport
across membranes.
Others of these proteins allow a bacterium to sense
its surrounding environments(e.g., as in chemotaxis).
Movement is via:
Simple Diffusion (including osmosis)
Facilitated Diffusion (with concentrationgradient & no energy expended)
Active Transport (against concentration
gradient & energy expended)
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impleD
iffusion--Osm
osis
solute
molecules/ions
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rotein-MediatedTran
sport
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ActiveTra
nsport
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The Prokaryotic Cell Wall
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The Prokaryotic Cell Wall
Determines cellshape.
Prevents osmoticlysis.
In some casesrecognized by host
immune system.
Target for
antibiotics.
Part of cell
envelope.
In Bacteria,composed of
Peptidoglycan.
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Gram-Pos vs. Gram-Neg.
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Gram-Positive Cell Envelope
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Gram-NegativeCellEnv
elope
cell wall
endotoxin
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Gram-Negative Cell Envelope
Periplasm: Site
of preliminary
nutrient
degradation.
LPS: Protection fromantibiotics such as
penicillin plus against
certain toxins.
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Lipopo
lysacch
aride(LPS)
Lipid A =Endotoxin
Carbohydrate has
negative charge and
provides protectionagainst some
antibiotics & some
toxins (e.g.,
detergents).
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MycoplasmalackCellW
alls
Note:
Pleomorphic
Mycoplasma pneumoniae causesWalking Pneumonia
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Glycoc
alyx
Protection (e.g.,
Streptococcus
pneumoniae fromphagocytosis)
Attachment (e.g.,
Streptococcus
mutans causing
dental plaques)
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Ca
psuleS
taining
Capsules are more
regular andgelatinous.
Slime Layers areless regular and
more diffuse.
http://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htm -
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Bacteria Flagella (plural)
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Flage
llarArrangeme
nts
also atrichous
e.g.,E. coli
Polar
Flagellum
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Chemo
taxis
Also
Phototaxis,
etc.
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Pili (sing. Pillus)
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Fimbriae (a kind of pilli)
Tips are Adhesins,
used to adhere, e.g.,
to animal tissues
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Closed Circular Chromosome
Also Plasmids, which are
smaller, circular pieces of
DNA.
Plasmids usually
encodeexpendable
functions, e.g.,
antibiotic
resistance.
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Ribosomes: Sites of Translation
On order of 10,000
per cell!
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Endosp
ores
Form inside of
vegetative cells
(hence endo).
Highly resistant toheat, U.V.,
desiccation, etc.
Characteristic of
many soil bacteria,
e.g., Bacillusspp.& Clostridium spp.
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