Unit - I HISTORY AND SCOPE

OF MICROBIOLOGY

Dr. R. Dhanapal Guest Lecturer of Zoology, M. R. G. A. C

Image : https://alchetron.com/Epulopiscium-fishelsoni

MICROBIOLOGY Study of

Microbes – too small to be seen with naked eye.

Less than 1mm in diameter.

Some are visible to the naked eye –

e.g.Bacterium Epulopiscium, filamentous

alga e, bread mould, mush rooms etc.

MICROBES

Extremely diverse group

• Bacteria ( Study of Bacteria -Bacteriology)

• Algae( Study of Algae - Phycology)

• Fungi ( Study of Fungi - Mycology)

• Viruses (Study of Viruses - Virology)

• Protozoa ( Study of Protozoa - Protozoology)

TYPES OF MICROBIOLOGY

Theoretical or Pure Microbiology

Practical or Applied Microbiology

THEORETICAL (PURE) MICROBIOLOGY • Study of occurrence

• Form

• Structure

• Classification

• Physiology

• Reproduction

• Heredity

• Variation and Evolution of microbes

APPLIED MICROBIOLOGY

Exploitation of beneficial microbes

Control the activities of harmful

microbes Types:

• Medical Microbiology – Study of role of microbes in

human & animal diseases.

• Agricultural Microbiology – Role of

microbes in plant diseases, soil fertility and spoilage of agricultural products.

• Industrial Microbiology - Utilisation of microbes for the production of alcoholic beverages, antibiotics, amino acids, organic acids –acetic acid, lactic acid, citric acid etc.

• Food Microbiology – Role of microbes in

food spoilage, their prevention and to increase the shelf life of various food products ; production of cheese, butter, fermented milk etc.

HISTORY OF MICROBIOLOGY

• Microbes – discovered in the late 17th century.

• First observed by Anton van Leeuwenhoek – Father of Microbiology.

• A Dutch draper - Hobby was lens grinding and microscope making.

• Made 550 crude single lens microscopes with magnification of 50x – 300 x.

Anton van Leeuwenhoek’s

Microscope

Anton van Leeuwenhoek’s observation of

microbes

• Leeuwenhoek examined rain water, saliva, pepper decoctions, cork, leaves of plants , seminal fluid, scrappings of teeth etc.

• Portrayed several microorganisms and

called them ‘Animal cules’.

• Conveyed his findings in a series of

letters to the British Royal Society, London during the mid 1670’s.

• Leeuwenhoek outlined the structural details of Paramecium, Amoeba, certain filamentous fungi, algae , bacteria etc.

• Scientists considered microbes only as

‘Curiosities of Nature’.

• Controversy regarding Spontaneous

generation (Abiogenesis) drew scientists to explore the origin and nature of living things.

• Spontaneous generation(Abiogenesis)

A belief in ancient times that living organisms could develop from non – living matter.

• Theory of Biogenesis – Living organisms

e only from preexisting organisms.

aris

Experiments to disprove Abiogenesis Redi’s Experiment (1688):

(Francesco Redi 1626

– 1697, Italian Physician)

Carried out a series of

experiments on decaying meat and its ability to produce maggo ts spontaneously.

Redi placed meat in 3

jars Jar 1 : Left open.

Flies laid eggs on meat - which developed into maggots .

Jar-2 : Covered with netting

• Flies laid eggs on

the netting – developed into maggots on the netting.

•

Jar-3 : Sealed

• No maggots developed on meat.

• This experiment proved that the maggots developed from fly eggs , not from meat .

• Thus Redi disproved the theory of spontaneous generation (Abiogenesis).

• In 1800s, the scientists believed that the infectious diseases were spread by an entity ‘miasms’- an altered chemical quality of atmosphere.

• Agostino Bassi (1773 – 1856) in 1835 demonstrated that a silk worm disease was due to a fungal infection – the first report

that a microorganism could cause disease.

Edward Jenner

• Edward Jenner in 1796, had used vaccination with materials from cow pox lesions to protect

peopl e against small pox.

1860 – 1910 : Golden age of

Microbiology

• Many research works

were conducted by Louis Pasteur (1822 – 1895), Robert Koch(1843 – 1910) and others.

• Many branches of Microbiology

Robert Koch

wer e established.

control of insects, care in the

• A series of discoveries , mostly involving identification of agents of diseases.

• Developed an awareness that infectious diseases were caused by microorganisms and the chain of transmission could be broken → led to sterilization practices in hospitals (Lister, 1867), pasteurization of milk, purification of water,

preparation of food fo consumption etc.

• Construction of a bacterial filter by Charles Chamberland (1884) made possible the discovery of viruses and their role in diseases.

• Dmitri Iwanowski (1892) discovered Tobacco Mosaic Virus (TMV) – the first viral pathogen studied.

• Microbiology contributed significantly to the development of Biochemistry – the discovery of cell free alcoholic fermentation by Buchner(1897) provided the key to chemical analysis of energy yielding processes.

.

processes brought about the activity of microbes li yeasts and bacteria.

theory of fermentation-

Contributions of Louis Pasteur-

Father of Industrial Microbiology • Put an end to the

theory of Abiogenesis.

• First demonstrated that air contain microbes.

• Discovered anaerobic life • Introduced the

terms aerobic and anaerobic.

• Established the Germ

chemical changes like fermentation are vital

k

• Established germ theory of disease – microorganisms are responsible for infectious diseases.

• Developed various methods of sterilization- steam sterilization, hot air oven, autoclave.

• Coined the term vaccine.

• Developed vaccines for anthrax and rabies.

Contributions of F.J. Cohn

• Discovered binary fission – the common method of multiplication in bacteria.

• Discovered endospores – certain bacteria form extremely resistant spores – Bacillus subtilis, Clostridium botulinum etc.

Contributions of Robert Koch

(1843 – 1910) Father of Medical

Microbiology

• First to relate a specific organism to a specific disease – the bacterium Bacillus anthracis causes anthrax.

• Also discovered Bacillus of tuberculosis

(Mycobacterium tuberculosis ) and the Cholera vibrio.

KOCH’S POSTULATES

• Robert Koch developed a series of procedures by which a specific organism could be related to a specific disease. These steps are called Koch’s postulates.

i) The microorganism must be present in every case of the disease but absent from healthy organisms.

ii) The suspected microorganism must be isolated and grown in a

pure culture.

iii) The same disease must result when the isolated microorganism is inoculated into a healthy host.

iv) The same micro organism must be isolated again from the diseased host.

By these procedures, a specific organism could be related to a specific disease.

• Also developed many staining methods for bacteria.

• Developed pure culture techniques • Use of solid culture medium to

grow bacteria.

• In the last decade of the 19 th century, microbiologist’s interests were concentrated on the role of microbes as agents of infectious diseases.

• Many of the important pathogenic organisms have been discovered and their casual roles established.

• The students of Pasteur, Koch and others discovered in rapid succession a group of bacteria capable of causing specific diseases , techniques and laboratory procedures.

• During the last decade of the 19th century, Microbiology became an established discipline with a distinct set of concepts and techniques.

• During the early part of 20 th century, Microbiology developed independently of other biological disciplines.

• Discovery of Electron microscope (1934) ,

Tissue culture technique etc.

Ernst Ruska & Max Knoll Electron microscope

Many antibiotics are produced from microbes.

• Development of drugs or chemicals which could kill infectious agents while being non-toxic to the host.

• In 1929 ,Sir Alexander Fleming discovered the antibiotic Penicillin from Penicillium notatum, which destroys Staphylococci – the first antibiotic produced from microorganisms.

• Microbiology established a closer relationship with other disciplines in 1940s.

• The first important connection between Genetics and Microbiology is the work of Beadle and Tatum (1941). They succeeded in isolating biochemical mutants in Neurospora crassa → one gene – one enzyme hypothesis.

Use of microbes to produce

valuable products→Industrial Microbiology.

• Development of rDNA technology (Gene cloning or Genetic Engineering).

• Genetically modified microbes that can

be used as factory cells for the synthesis of valuable pharmaceutical products like human insulin, hormones, vaccines etc.

• Space Microbiology ( a branch of Exobiology- investigating the possibility of extraterrestrial life and the effects of extraterrestrial environments on living organisms from the earth. ) investigates the possibility of using microbes as sources of food and oxygen.

Modern Microbiology is a well

developed discipline with

established concepts and

techniques.

SCOPE OF MICROBIOLOGY

Many microbiologists focus on a specific group of microorganisms.

• Virologists – on Viruses

• Bacteriologists – on Bacteria

• Phycologists – on Algae

• Mycologists – on Fungi

• Protozoologists –on Protozoa.

Different fields :

• Microbial Morphology

• Microbial Physiology

• Microbial Cytology

• Microbial Ecology

• Microbial Genetics & Molecular Biology

• Microbial Taxonomy

• Medical Microbiology

• Public health Microbiology

• Food Microbiology

• Dairy Microbiology

• Immunology

Microbes - Extremely useful as experimental materials.

• Simple

• Grow rapidly

• Can culture in large quantities in test tubes, flasks, require less space and maintenance than large plants and animals.

• Easy – to – work –with material for studying complex processes of

metabolism.

• Metabolic processes – similar to higher plants and animals

• Microbes can be used to study synthesis of antibiotics ,toxins, energy production, survival mechanism in harsh environmental conditions, microbial nitrogen fixation etc.

THANK YOU