1. MICROBIOLOGY AND IMMUNOLOGY (BIOL200/343), SUMMER, 2017
Lecture:3
MICROBIOLOGY AND IMMUNOLOGY (BIOL200/343), SUMMER, 2017
Dr.Q.M.I.Haq

2. Microbes can be classified into four major groups: 1. Bacteria
Classification of Microorganisms:
Microbes can be classified into four major groups:
1. Bacteria
2. Virus
3. Fungi
4. Protozoa

3. Basic structure of bacteria

4. Bacteriology is the study of bacteria.
Bacteria are prokaryotic, unicellular organisms containing DNA and ribosomes.
Bacteria have ALL the characteristics of living things.
Bacteria have the greatest percentage of the biomass on Earth!

5. Bacteria are unicellular prokaryotic microorganisms that multiply by binary fission.
Bacteria can be classified according to morphology, arrangement, and staining reaction into the following groups:
1- Filamentous bacteria: Streptomyces: antibiotic producers.
2- True bacteria:
Cocci: Gram positive: Staphylococcus, Streptococcus.
` Gram negative: Neisseria.
Bacilli: Gram positive: Bacillus, Clostridum, Corynebacterium.
Gram negative: Enterobacteriaceae, Brucella.
3- Spirochetes: Slender flexuous spiral bacteria.
Borrelia, Treponema, Leptospira.
4- Mycoplasma: The Smallest bacteria that lack of a rigid cell wall.
5- Rickettsiae and Chlamydiae: intracellular parasites.

6. The size of bacteria
The size of bacteria is measured in micrometer (m) or micron () (1 micron or micrometer is one thousandth of a millimeter) and varies from 0.1  to .
Most pathogenic bacteria measure from 0.1 to 10 .

7. Structure of bacterial cells: Size, Shape, and Arrangement of bacterial cells:
Morphology and arrangement of bacterial cells are criteria used for classification of
bacteria into following groups:
1. Cocci (Singular: coccus).
2. Rods (bacilli), (Singular: rod, bacillus).
3. Vibrios (Singular: vibrio).
4. Spirilla (singular :Spirillum)
5. Spirochetes. (Singular: Spirochaete).
1. Cocci:
-These are round or oval bacteria measuring about micrometer in diameter.
-When they multiplying, cocci may form pairs, chains, or irregular groups.
-Cocci in pairs are called diplococci, for example, meningococci and gonococci.
-Cocci in chains are called streptococci, for example Streptococcus pyogens.
-Cocci in irregular groups are called Staphytococci, for example, Staphylococcus
aureus.

8. Spherical (cocci) bacteria
a. Micrococci
Diplococci
Streptococci
b. Tetracocci
c. Sarcine
d. Staphylococci

9. 2. Rods (bacilli):
-These are stick-like bacteria with rounded, square, or swollen ends. -They measure 1-10 micrometer in length by micrometer in width. -It may arranged in: A- Chains, for example, Streptobacillus species. B- Branching chains, for example, lactobacilli . C- Mass together, for example, Mycobacterium leprae. D- Remain attached at various angles resembling Chinese letters, for example, Corynebacterium diphtheria.

10. - Spirochetes are divided into three main groups:
3-Vibrios:
-These are small slightly curved rods measuring 3-4 micrometer in length by 0.5 micrometers in width. -Most vibrios are motile with a single flagellum at one end. -They show a rapid darting motility. For example: vibrio cholerae.
4-Spirochetes:
-These are flexible, coiled, motile organism, 6-20 micrometer in length.
- Spirochetes are divided into three main groups:
A- Treponemes B- Borreliae C- Leptospires.

11. Cell wall
In addition to conferring rigidity upon bacteria, the cell wall protects against osmotic damage.
Chemically, the rigid part of the cell wall is peptidoglycan.
First described by Hans Christian Gram in It is' used to study morphologic appearance of bacteria. Gram's stain differentiates all bacteria into two distinct groups:
a. Gram-positive organisms
b. Gram-negative organisms

13. Morphology of Rickettsiae.
They are minute organisms having properties in between bacteria and viruses.
It contains both DNA and RNA.
It is coccobacilli 300x600 nm in size, non-motile, and is Gram-negative.
Sensitive to many antibiotics.
Can multiply only inside living cells.
Morphology of chlamydia.
Chlamydiae are Gram-negative.
They are intracellular parasites.

14. Bacteria have a variety of important uses:
Help make interesting food (buttermilk, yogurt, cheese, sauerkraut, pickles, and olives, etc…)
Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simpler compounds)
Nitrogen fixation (chemically changes nitrogen gas, N2, into ammonia, NH3, so plants can make amino acids)
Human health (bacteria on skin help prevent infection & bacteria in gut helps digest food & make vitamins)
Biotechnology (used to make antibiotics, insulin, human growth hormone, vitamins, and other drugs).

15. A rather vocal minority (less than 1%) of bacteria cause disease in humans, animals, and plants.
Bacteria can cause a variety of diseases:
Food Poisoning – Scarlet Fever
Tuberculosis – Whooping Cough
Cholera – Bacterial Meningitis
Syphilis – Pneumonia
Ulcers – Leprosy
Strep Throat – Tetanus

16. How Do Pathogenic Bacteria Work?
Bacteria produce disease in one of two ways:
Using cells for food: The bacteria break down healthy cells for food, destroying tissues
Releasing toxins: The bacteria produce a toxin (poisonous protein) that is released into the bloodstream where it can travel throughout the body, disrupting normal activity and damaging tissues