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TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
Dr. Fadilah Sfouq
Female department
2015
What is a Microbe?
What is microbiology?
• Smaller than 0.1mm and are usually too
small to be seen with the unaided eye
– Includes bugs, germs, viruses, protozoan,
bacteria.
• The branch of biology dealing with the
structure, function, uses, and modes of
existence of microscopic organisms
Why study Microbiology
• Microbes are related to all life.
– In all environments
– Many beneficial aspects
– Related to life processes (food web,
nutrient cycling)
– Only a minority are pathogenic.
– Most of our problems are caused by
microbes
Chapter 4, part A
• Functional Anatomy of
Prokaryotic and Eukaryotic Cells
Objectives
Compare and contrast the overall cell structure of prokaryotes and
eukaryotes.
Identify the three basic shapes of bacteria.
Describe structure and function of the glycocalyx, flagella, axial filaments,
fimbriae, and pili.
Compare and contrast the cell walls of gram-positive bacteria, gram-negative
bacteria, acid-fast bacteria, and mycoplasmas.
Describe the structure, chemistry, and functions of the prokaryotic plasma
membrane.
Identify the functions of the nuclear area, ribosomes, and inclusions.
Describe the functions of endospores, sporulation, and endospore
germination.
What you should remember from Biochemistry:
Define organelle. Describe the functions of the nucleus, endoplasmic
reticulum, ribosomes, Golgi complex, lysosomes, vacuoles, mitochondria,
chloroplasts, peroxisomes. Explain endosymbiotic theory of eukaryotic
evolution.
Three Domain Classification
• Bacteria
• Archaea
• Eukarya
– Protista
– Fungi
– Plants
– Animals
Types of Microorganisms
• Bacteria
• Archaea
• Fungi
• Protozoa
• Algae
• Viruses
• Multicellular animal parasites
• Prions
Prokaryotic Cells
• Comparing Prokaryotic and Eukaryotic
Cells
– Prokaryote comes from the Greek words
for prenucleus.
– Eukaryote comes from the Greek words
for true nucleus.
Comparing Prokaryotic and
Eukaryotic Cells
Common features:
DNA and chromosomes
Cell membrane
Cytosol and Ribosomes
Distinctive features: ?
Prokaryote
• One circular
chromosome, not in
a membrane
• No histones
• No organelles
• Peptidoglycan cell
walls
• Binary fission
Eukaryote
• Paired
chromosomes, in
nuclear membrane
• Histones
• Organelles
• Polysaccharide
cell walls
• Mitotic spindle
• Average size: 0.2 -1.0 µm  2 - 8 µm
• Basic shapes:
• Unusual shapes
– Star-shaped Stella
– Square Haloarcula
• Most bacteria are monomorphic
• A few are pleomorphic
Arrangements
• Pairs:
diplococci,
diplobacilli
• Clusters:
staphylococci
• Chains:
streptococci,
streptobacilli
Glycocalyx
• Outside cell wall
• Usually sticky
• A capsule is neatly
organized
• A slime layer is
unorganized &
loose
• Extracellular
polysaccharide
allows cell to attach
• Capsules prevent
phagocytosis
Flagella
• Outside cell wall
• Made of chains of
flagellin
• Attached to a
protein hook
• Anchored to the
wall and
membrane by the
basal body
Flagella Arrangement
• Fimbriae allow
attachment to
surfaces
• Pili are used to
transfer DNA
from one cell to
another
Motility
• Due to rotation of flagella
• Mechanism of rotation: “Run and tumble”
• Move toward or away from stimuli (taxis)
Cell Wall
• Prevents osmotic lysis
• Made of peptidoglycan (in bacteria)
Peptidoglycan
• Polymer of disaccharide
N-acetylglucosamine (NAG) & Nacetylmuramic acid (NAM)
• Linked by polypeptides
Gram +
Cell Wall
• Thick layer of
peptidoglycan
• teichoic acid on
surface
Gram –
Cell Wall
• Thin peptidoglycan
• No teichoic acids
• Outer membrane
– LPS
– O - polysaccaride
– Lipid A
Gram-Positive cell walls
• Teichoic acids:
– Lipoteichoic acid links to plasma membrane
– Wall teichoic acid links to peptidoglycan
• May regulate movement of cations
• Polysaccharides provide antigenic variation
Gram-Negative Outer Membrane
• Lipopolysaccharides, lipoproteins,
phospholipids.
• Forms the periplasm between the outer
membrane and the plasma membrane.
• Protection from phagocytes, complement,
antibiotics.
• O polysaccharide antigen, e.g., E. coli
O157:H7.
• Lipid A is an endotoxin.
• Porins (proteins) form channels through
membrane
Gram-Negative Outer Membrane
Figure 4.13c
Gram Stain Mechanism
• Crystal violet-iodine crystals form in cell
• Gram-positive
– Alcohol dehydrates peptidoglycan
– CV-I crystals do not leave
• Gram-negative
– Alcohol dissolves outer membrane and leaves
holes in peptidoglycan
– CV-I washes out
Atypical Cell Walls
• Mycoplasmas
– Lack cell walls
– Sterols in plasma membrane
• Archaea
– Wall-less, or
– Walls of pseudomurein (lack NAM and D amino
acids)
Damage to Cell Walls
• Lysozyme digests disaccharide in
peptidoglycan.
• Penicillin inhibits peptide bridges in
peptidoglycan.
• Protoplast is a wall-less cell.
• Spheroplast is a wall-less Gram-positive cell.
• L forms are wall-less cells that swell into
irregular shapes.
• Protoplasts and spheroplasts are susceptible
to osmotic lysis.
Plasma Membrane
Figure 4.14a
•
•
•
•
Plasma Membrane
Phospholipid bilayer
Peripheral proteins
Integral proteins
Transmembrane proteins
Figure 4.14b
Fluid Mosaic Model
• Membrane is as
viscous as olive oil.
• Proteins move to
function
• Phospholipids rotate
and move laterally
Figure 4.14b