Cell Structure and Function in Bacteria and Archaea

31 Pages·2013·1.43 MB·English

by  System 103

10/5/2013
LECTURE PRESENTATIONS
For BROCK BIOLOGY OF MICROORGANISMS, THIRTEENTH EDITION
Michael T. Madigan, John M. Martinko, David A. Stahl, David P. Clark
Chapter 3
Cell Structure and
Function in Bacteria
Lectures by
John Zamora and Archaea
Middle Tennessee State University
© 2012 Pearson Education, Inc.
I. Cell Shape and Size
• 3.1 Cell Morphology
• 3.2 Cell Size and the Significance of
Smallness
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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3.1 Cell Morphology
• Morphology = cell shape
• Major cell morphologies (Figure 3.1)
– Coccus (pl. cocci): spherical or ovoid
– Rod: cylindrical shape
– Spirillum: spiral shape
• Cells with unusual shapes
– Spirochetes, appendaged bacteria, and
filamentous bacteria
• Many variations on basic morphological types
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
Figure 3.1 Representative cell morphologies of prokaryotes
Coccus Spirochete

Coccus cells may also exist as short chains
or grapelike clusters
Stalk Hypha
Rod Buddin g and
appendaged bacteria

Spirillum

Filamentous bacteria

© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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3.1 Cell Morphology
• Morphology typically does not predict physiology1,
ecology, phylogeny2, etc. of a prokaryotic cell
• Selective forces may be involved in setting the
morphology
– Optimization for nutrient uptake (small cells and
those with high surface-to-volume ratio)
– Swimming motility in viscous environments or
near surfaces (helical or spiral-shaped cells)
– Gliding motility (filamentous bacteria)
1 functions and activities of living organisms and their parts
2 the evolutionary history of a group of organisms
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.2 Cell Size and the Significance of
Smallness
• Size range for prokaryotes: 0.2 µm to >700 µm in
diameter
– Most cultured rod-shaped bacteria are between
0.5 and 4.0 µm wide and <15 µm long
– Examples of very large prokaryotes
• Epulopiscium fishelsoni (Figure 3.2a)
• Thiomargarita namibiensis (Figure 3.2b)
• Size range for eukaryotic cells: 10 to >200 µm in
diameter
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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Figure 3.2 Some very large prokaryotes
Epulopiscium fishelsoni
Thiomargarita namibiensis
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.2 Cell Size and the Significance of
Smallness
• Surface-to-Volume Ratios, Growth Rates, and
Evolution
– Advantages to being small (Figure 3.3)
• Small cells have more surface area relative to cell
volume than large cells (i.e., higher S/V)
– support greater nutrient exchange per unit cell
volume
– tend to grow faster than larger cells
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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Figure 3.3 Surface area and volume relationships in cells
r = 1 m
r = 1 m
Surface area (4r2) = 12.6 m2

Volume ( 4 r3) = 4.2 m3
3

Surface
Volume = 3

r = 2 m
r = 2 m
Surface area = 50.3 m2

Volume = 33.5 m3

Surface
Volume = 1.5

© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.2 Cell Size and the Significance of
Smallness
• Lower Limits of Cell Size
– Cellular organisms <0.15 µm in diameter are
unlikely
– Open oceans tend to contain small cells (0.2–
0.4 µm in diameter)
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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II. The Cytoplasmic Membrane and
Transport
• 3.3 The Cytoplasmic Membrane
• 3.4 Functions of the Cytoplasmic Membrane
• 3.5 Transport and Transport Systems
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.3 The Cytoplasmic Membrane in
Bacteria and Archaea
• Cytoplasmic membrane:
– Thin structure that surrounds the cell
– 6-8 nm thick
– Vital barrier that separates cytoplasm from
environment
– Highly selective permeable barrier; enables
concentration of specific metabolites and
excretion of waste products
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3.3 The Cytoplasmic Membrane
• Composition of Membranes
– General structure is phospholipid bilayer
(Figure 3.4)
• Contain both hydrophobic and hydrophilic
components
– Can exist in many different chemical forms as a
result of variation in the groups attached to the
glycerol backbone
– Fatty acids point inward to form hydrophobic
environment; hydrophilic portions remain exposed
to external environment or the cytoplasm
Animation: Membrane Structure
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
Figure 3.4 Phospholipid bilayer membrane Glycerol

Fatty acids

Phosphate

Ethanolamine

Hydrophilic General architecture
region of a bilayer
membrane; the blue
Hydrophobic
Fatty acids balls depict glycerol
region
with phosphate and

Hydrophilic (or) other hydrophilic
r egion groups.

Glycerophosphates

Fatty acids

© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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3.3 The Cytoplasmic Membrane
• Cytoplasmic Membrane (Figure 3.5)
– 6-8 nm wide
– Embedded proteins
– Stabilized by hydrogen bonds and hydrophobic
interactions
– Mg2+ and Ca2+ help stabilize membrane by forming
ionic bonds with negative charges on the
phospholipids
– Somewhat fluid
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
Figure 3.5 Structure of the cytoplasmic membrane
Out

Phospholipids Hydrophilic
g roups

6–8 nm
Hydrophobic

groups

In

Integral
m embrane Phospholipid
proteins molecule

© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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3.3 The Cytoplasmic Membrane
• Membrane Proteins
– Outer surface of cytoplasmic membrane can
interact with a variety of proteins that bind
substrates or process large molecules for transport
– Inner surface of cytoplasmic membrane interacts
with proteins involved in energy-yielding reactions
and other important cellular functions
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.3 The Cytoplasmic Membrane
• Membrane Proteins (cont’d)
– Integral membrane proteins
• Firmly embedded in the membrane
– Peripheral membrane proteins
• One portion anchored in the membrane
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3.3 The Cytoplasmic Membrane
• Membrane-Strengthening Agents
– Sterols
• Rigid, planar lipids found in eukaryotic membranes
Strengthen and stabilize membranes
– Hopanoids
• Structurally similar to sterols
• Present in membranes of many Bacteria
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
3.3 The Cytoplasmic Membrane
• Archaeal Membranes
– Ether linkages in phospholipids of Archaea
– Bacteria and Eukarya that have ester linkages in
phospholipids
– Can exist as lipid monolayers, bilayers, or mixture
(Figure 3.7d and e)
© 2012 Pearson Education, Inc. Marmara University – Enve303 Env. Eng. Microbiology – Prof. BARIŞ ÇALLI
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