MicrobiologyAN INTRODUCTION

EIGHTH EDITION

TORTORA • FUNKE • CASE

Dr. Fadilah SfouqFemale 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 chromosomesCell membraneCytosol and Ribosomes

Distinctive features: ?

• One circular chromosome, not in a membrane

• No histones

• No organelles

• Peptidoglycan cell walls

• Binary fission

Prokaryote 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

• Pairs: diplococci, diplobacilli

• Clusters: staphylococci

• Chains: streptococci, streptobacilli

Arrangements

• 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

Glycocalyx

• Outside cell wall

• Made of chains of flagellin

• Attached to a protein hook

• Anchored to the wall and membrane by the basal body

Flagella

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)

• Prevents osmotic lysis

• Made of peptidoglycan (in bacteria)

Cell Wall

• Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)

• Linked by polypeptides

Peptidoglycan

Gram + Cell Wall

• Thick layer of peptidoglycan

• teichoic acid on surface

• Thin peptidoglycan

• No teichoic acids

• Outer membrane– LPS– O - polysaccaride– Lipid A

Gram – Cell Wall

• Teichoic acids:– Lipoteichoic acid links to plasma membrane– Wall teichoic acid links to peptidoglycan

• May regulate movement of cations

• Polysaccharides provide antigenic variation

Gram-Positive cell walls

• 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

Gram-Negative Outer Membrane

Figure 4.13c

• 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

Gram Stain Mechanism

• Mycoplasmas– Lack cell walls– Sterols in plasma membrane

• Archaea– Wall-less, or– Walls of pseudomurein (lack NAM and D amino

acids)

Atypical 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.

Damage to Cell Walls

Plasma Membrane

Figure 4.14a

Plasma Membrane• Phospholipid bilayer

• Peripheral proteins

• Integral proteins

• Transmembrane proteins

Figure 4.14b

• Membrane is as viscous as olive oil.

• Proteins move to function

• Phospholipids rotate and move laterally

Fluid Mosaic Model

Figure 4.14b