Microbiology and Microorganisms

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GENERAL MICROBIOLOGY
Microbial World, History and Development of Microbiology, Scope of Microbiology
Dr. (Mrs) S. Sharma
Professor
Department of Microbiology
CCS Haryana Agricultural University
Hisar-125001
and
Dr. Neeraj Dilbaghi
Reader
Department of Biotechnology
Guru Jambheshwar University of Science & Technology
Hisar-125001
01-May-2006 (Revised 12-Dec-2006)
CONTENTS
Introduction
Historical Developments
Leeuwenhoek’s Findings
Biogenesis versus Abiogenesis
Contributions of Pasteur
Contributions of Robert Koch and Germ Theory of Disease
Rise of Medical Microbiology
Microorganisms as Geochemical Agents
Microbiology in the Twentieth Century
Activities of microorganisms important in our daily life
Scope of Microbiology
Some recent applications of bacteria
Keywords
Microorganisms, microscope, fermentation, disease Introduction Microbiology, the study of microscopic organisms, derived its name from three Greek words: mikros (“small”), bios (“life”), and logos (“science”). Taken together they mean the study of microorganisms which are very small and cannot be seen by unaided eye. If an object has a diameter 0.1 mm or less, eye cannot see it and very little details can be seen in an object having diameter 1 mm. So roughly speaking organisms having diameter 1 mm or less are called microorganisms and are studied in Microbiology.

Although microorganisms are ancient by many standards, microbiology itself is a comparatively new science. The existence of microorganisms was unknown until the discovery of Microscope. Microscope is an optical instrument which can magnify small objects which cannot be seen by naked eye. Microscopes were invented in the beginning of 17th century. Early Microscopes were of two types; Simple Microscope, with a single lens of very short focal length and Compound Microscope, with two double convex lens system including ocular and objective lens with higher magnifying power. Most of the epoch making original discoveries about microorganisms was all made using simple and compound microscopes.

Characteristics of microorganisms
1. Their size is very small.
2. There is no cellular differentiation. They are unicellular and one cell is capable of performing all the functions. Some microorganisms are multicellular with little or no cellular differentiation.

3. Microorganisms are present everywhere on the bodies of animals and humans, on plant surfaces, in the air, water, dust, soil, and even inside the intestinal canal of all insects, birds, animals and human beings.

Taxonomic Groups
Microorganisms have wide taxonomic distribution and include organisms such as protozoa, algae, fungi, bacteria and virus.The schematic illustrations of different microorganisms are shown in Figure S.1.

Protozoa are unicellular eukaryotic organisms, motile having cilia, flagella and pseudopodia, saprophytic or parasitic. They are generally present in soil, water and marshy places and their size varies from 5-200 µm. They are animal-like in that they ingest particulate food, lack a rigid cell wall, do not contain chlorophyll. The study of protozoa is known as protozoalogy. They are differentiated on the basis of morphological, nutritional and physiological characteristics. Their role in nature is varied, but the best known protozoa are the few that cause disease in human beings and animals, such as malaria in humans. Some protozoa are beneficial, such as those found in stomach of cattle, sheep and termites that help digest food. Algae are relatively simple organisms, their size varies from 1 µm to several feet. They are considered plant-like because they contain the green pigment chlorophyll, carry out photosynthesis, and have rigid cell walls. They are unicellular to multicellular and either motile or nonmotile. The study of algae is known as Algology or Phycology. These organisms are autotrophic and are found most commonly in aquatic environments or in...
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