2. History and Taxonomy

Question 1

Cell Theory

Answer 1

• All organisms made up of one or more cells -> fundamental unit of structure and function
• All cells from pre-existing cells by division
• All vital functions of organisms occur within cells
• cells contain hereditary information -> regulating cell functions -> transmitting information to next generation of cells

Question 2

What is the Germ Theory?

Answer 2

1.) Hippocratic concept of disease

Disease caused by:
-> Climate (malaria)
-> Hereditary
-> Regimen
=> Humoral imbalance
(blood, bile)
Treatment:
-> Environment, exercise, diet, blood-letting, surgery

2.) Microbiological concept of disease

Disease caused by:
-> Germs -> Infection

Treatment:
-> Vaccination, antibiotics

Question 3

Pasteur and Germ theory

Answer 3

• proofed validity of germ theory

a) non-sterile liquid poured into flask
b) neck of flask drawn out in flame
c) liquid sterilised by extensive heating

    => pasteurization

d) liquid cooled slowly -> long time -> liquid remains sterile indefinitely
e) flask tipped so microorganism-laden dust contacts sterile liquid -> short time -> microorganisms grow in liquid

Question 4

Isolation of microorganisms

Answer 4

There are various techniques to isolate microorganisms in pure cultures or axenic cultures

-> Streak plate technique of isolation

-> The method of serial dilutions
(Pour plate / spread plate techniques of isolation)

Question 5

Koch’s Postulates

Answer 5

1. The suspected pathogenic organism should be present in all cases of the disease and absent from healthy animals

Tools used: Microscopy and staining

Observe the blood and tissue of the diseased and healthy animal under the microscope in order to identify the suspected pathogen

2. The suspected organism should be grown in pure culture

Tools used: Laboratory culture

Streak agar plate with sample from either diseased or healthy animal (suspected pathogen on agar plate)

• > Inoculate healthy animal with cell of suspected pathogen
  3. Cells from a pure culture of the suspected organism should cause disease in a healthy animal

Tools used: Experimental animal

• > Remove blood or tissue sample and observe by microscopy
  4. The organism should be re isolated and shown to be the same as the original

Tools used: Laboratory re isolation

Suspected pathogen is grown as a laboratory culture (Pure culture must be same organism as before)