BACTERIA

CLS 311: Basic Microbiology

Mrs. Ohoud alhumaidan

OUTLINE

History

Prokaryote

Introduction

Bacteria size & shape ( Morphology + arrangement)

Reproduction

Classification

Structure of bacterial cell

1. Capsule

2. Cell wall

3. Cell membrane ( cytoplasmic membrane)

4. Cytoplasm , chromosome and plasmid

5. Flagella

6. Pilli

7. Endospore

HISTORY

Anton van Leeuwenhoek

Louis Pasteur

Robert Koch

MICROORGANISMS

A cellular

Cellular

Prokaryotes Eukaryotes

Archaea

Bacteria

Viruses

Protozoae

Fungi .

PROKARYOTES

There are two major types of prokaryotes: 1. Bacteria.

2. Archaea (also called archaebacteria)

Prokaryotic cells possess simpler structures than eukaryotic cells ,

INTRODUCTION

Bacteriology

Bacteria (plural), Bacterium (singular).

Binary fusion

Generation time

BACTERIA SIZE & SHAPE

Size :

Ranging between 0.2m to 10.0 m in length

Unit of microbial measurement is the micrometer (m), formerly micron () which is equal to:

1m = 1/1000 of a millimeter (mm)

Shape ( morphology ) 1) Rods ( bacilli )

2) Cocci

3) Spiral or curved shape

4) pleomorphic

BACTERIAL MORPHOLOGY

1- Shape:

Bacilli (bacillus, singular) – rod shaped organisms

Cocci (coccus, singular) – spherical or round organisms

Spirilla (spirillum, singular) – spiralled or comma-shaped organisms

BACTERIAL MORPHOLOGY

2-Arrangement : A- cocci

BACTERIAL MORPHOLOGY

2-Arrangement : B- bacilli

REPRODUCTION

Binary fission

Two factors that affect bacterial

arrangements:

• Plane of division

• Position taken after cell division

REPRODUCTION

Cocci arrangement Example

diplococci Neisseria gonorrhea

Chains Streptococci,

Grapelike clusters Staphylococci

Groups of four (tetrads ) Peptococcu

Packets of eight Sarcinae

CLASSIFICATION

Kingdom Bacteria

Phylum Proteobacteria

Class Gamma Proteobacteria

Order Enterobacteriales

Family Enterobacteriaceae

Genus Escherichia

Species Escherichia coli

e.g. Escherichia coli

STRUCTURE OF BACTERIAL CELL ( CHECK CHAPTER 3)

Cell Envelope :

Made up of two to three layers:

1. Cell wall .

2. Cell membrane .

3. Capsule : (in some species of bacteria )

STRUCTURE OF BACTERIAL CELL

1- CAPSULE

Made of polysaccharide

Can be detected by capsule staining (

negative stain )

Function of bacterial capsule

2- CELL WALL

cell wall provides strength , rigidity and protection

Peptidoglycan

Classification of bacteria according to cell wall :

1- have cell wall : Gram positive & Gram negative

2- lack of cell wall : e.g. : Mycoplasma ( AFB )

PEPTIDOGLYCAN

Gram stain

DIFFERENCES BETWEEN G+ & G -- (CHECK TABLE 4-5 ( CHAPTER 4)

Gram positive

Gram negative

DIFFERENCES BETWEEN G+ & G- CELL WALL FIGURE 3-8 (CHAPTER 4)

3-CELL MEMBRANE

CYTOPLASM & CHROMOSOME & PLASMID

Cytoplasm:

It is a gel-like matrix composed of water, enzymes,

nutrients, wastes, and gases .

Chromosome :

bacterial cells possess only one chromosome .

Plasmid :

Plasmids are small extrachromosomal genetic structures carried

by many strains of bacteria.

Like the chromosome, plasmids are made of a circular piece of

DNA. Unlike the chromosome, they are not involved in

reproduction.

FLAGELLA

Flagella (singular, flagellum) are long hair-like

structures that can be found at either or both ends of

a bacterium or all over its surface.

Function of the Flagella

PILLI

Many species of bacteria have pili (singular, pilus),

short hair-like structures emerging from all around

the outside cell surface.

Type of Pilli :

Function of the Pilli :

ENDOSPORES

Bacterial spores called endospore

Sporulation

Eg ; clostredium , Bacillus

Function of endospores

Several species of endospore-formers can

cause a disease :

clostridium botulinum>> botulism

Clostridium tetani >> tetanus

Clostridiun prefrenges >>gas gangren