Download Prokaryotic Cell Structure

Prokaryotic Cell Shapes
Prokaryotic Cell Structure
„ 3 Main Shapes
Rods
Cocci
„ Spirals
„
„
„
„
Spirochetes Æ flexible
Spirillum Æ stiff
Chapter 3
Prokaryotes vs Eukaryotes
Prokaryotes
Eukaryotes
DNA
Other Prokaryotic Shapes
„ Coccobacillus
„ Vibrio
„ Pleomorphic
Organelles
Size &
Organization
Kingdoms
Where do viruses fit in?
Typical Prokaryotic Cell
„ Acellular microorganisms
Cannot reproduce outside of host cell
„ No metabolism outside of host cell
„ RNA or DNA – never both
„
Fimbriae
„ Debate: living or non-living?
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Prokaryotic Cell Structures
Capsule
„ External structures
Glycocalyx
Flagella
„ Pili / fimbriae
„ Cell wall
„ Gram-positive and Gram-negative
„ Cell membrane
„ Internal structures
„ DNA, RNA, proteins
„ Ribosomes
„ Endospores
„
„
Glycocalyx
Slime layer
„ Made of polysaccharides, polypeptides, or
„ Loosely attached
both
„ Two types
„ Water soluble
Capsule
„ Slime Layer
„
„ Functions:
„
„
Protection
Attachment
„
Capsule
Biofilms
Flagella
„ Organized
„ Firmly attached
„ Functions:
„
„
Protection
Virulence factor
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Flagella
Function of Flagella
„ Filament, hook, and
„ Movement
basal body
„ Filament made of
flagellin
„ Filament can rotate
360º
Flagella arrangements
„
Rotate counterclockwise or clockwise
„ Runs
„ Tumbles
Fimbriae
Monotrichous
Lophotrichous
Flagella arrangements
Pili
„ Hollow tubules
„
Amphitrichous
„
Regular pili
Conjugation pili
Peritrichous
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Fimbriae and Pili
Gram-positive cell walls
„ Gram-stain purple
„ Thick layer of
peptidoglycan
„ Teichoic acids and
lipoteichoic acids
present
Bacterial Cell Walls
Gram Stain (Gram-positive)
„ Composed of peptidoglycan
„
Polymer of N-acetylmuramic acid (NAM) and
N-acetyl glucosamine (NAG)
„ Attached by tetrapeptide crossbridges
Types of bacterial cell walls
Gram+ Genera Examples
„ Gram-positive
„ Bacillus
„
Thick layer of peptidoglycan
„ Gram-negative
„
Thin layer of peptidoglycan plus an outer
membrane
„ Clostridium
„ Streptococcus
„ Staphylococcus
„ Listeria
„ Corynebacterium
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Acid-fast cells
Gram-negative cell walls
„ Gram-positive cells
„ Gram-stain pink
„ Extra stuff in cell wall
„ Thin layer of
Mycolic acid
„ Resistant
„
„ Special staining
procedure – Acid fast
stain
peptidoglycan
„ Outer membrane
„ Periplasmic space
between inner &
outer membranes
Acid Fast Stain
Gram Stain (Gram-negative)
Acid-Fast Genera Examples
Gram- Genera Examples
„ Mycobacterium
„ Escherichia
„ Nocardia
„ Salmonella
„ Shigella
„ Bordetella
„ Neisseria
„ Pseudomonas
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Gram-negative outer membrane
Bacteria without Cell Walls
„ Also called cell envelope
„ Mycoplasma
„ Phospholipid bilayer
„
„
„
Lipopolysaccharide (LPS)
„ Lipid + sugar
„ Also known as endotoxin
„ Lipid portion known as lipid A
„ Released from dead/damaged cells
„ May trigger fever, vasodilation,
inflammation, shock, and
disseminated intravascular
coagulation (DIC)
„ Can be released when antimicrobial
drugs kill bacteria
Sterols in cell membrane
„ Chlamydia
Lipopolysaccharides
„ Porins
„ Other proteins
„
Cell membrane + outer membrane
No peptidoglycan
Prokaryotic Cytoplasmic Membrane
Sugar
Lipid A
Periplasmic space
Functions of Cytoplasmic Membrane
„ Between outer membrane and cell membrane
„ Selectively permeable
„
Contains peptidoglycan and periplasm
„ Energy production
„
Proton motive force (PMF)
„ Photosynthesis
„
photosynthetic prokaryotes
Periplasmic space
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Internal Prokaryotic Structures
Endospore Formation
„ Cytosol
„ Inclusions
„ Ribosomes
„ Cytoskeleton
Mother cell
(keratin)
Spore core
(Dipicolinic acid
+ calcium)
Prokaryotic Ribosomes
(peptidoglycan)
Spore structure
Outer Spore Coat
(Exosporium)
Spore Coat
50S
Outer membrane
70S
Cortex
30S
Inner membrane
S = Svedberg unit
Spore Core
Endospores
Types of Endospores
„ Formed by Bacillus and Clostridium
„ Defensive strategy
„
„
Metabolically inactive
Germinate in favorable conditions
Terminal
Central
Subterminal
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Endospore Stain
Cell Division
„ Budding
Cell Division in Prokaryotes
Cell Arrangements
„ Asexual
„ Result from
„ Binary fission is
„
most common
„
Plane of cell division
Extent of separation of daughter cells
„ Cocci Æ multiple planes
„ Bacilli Æ single plane
Coccus
Cell Division
Bacillus
Arrangements of Cocci
„ Snapping division
„
Palisades and Vhapes
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Arrangements of Bacilli
Eukaryotic organelles
„ Membrane-bound organelles
Nucleus
Endoplasmic reticulum
„ Golgi apparatus
„ Lysosome
„ Mitochondria
„ Chloroplast
„
„
What about Eukaryotes?
Mitochondria & Chloroplasts
„ Some have flagella
„ Surrounded by phospholipid bilayer
Different structure than prokaryotes
„ Similar to eukaryotic cilia
„
„ Contain a circular molecule of DNA
„ Contain 70S ribosomes
„ Some have a glycocalyx
„
Less organized than prokaryotes
„ Some have cell walls
„
„
Plants, fungi, algae
Polysaccharides such as cellulose & chitin
What about Eukaryotes?
Cell Division in Eukaryotes
„ All have a cell membrane
„ Mitosis
Phospholipid bilayer
„ Capable of endo- and exocytosis
„
„ Meiosis
„ All have ribosomes
„
80S ribosomes – 40S + 60S
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Last but not least . . . Nomenclature!
„ Genus + species
„ Escherichia coli
„ E. coli
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