Microbiology is the study of microscopic living organisms, the microbes that are usually too small to be seen with the unaided eye. Microorganisms are extremely diverse and ubiquitous in nature. Microbiology deals with the study of distribution of microorganisms in nature, their unique metabolic characteristics, their relationship with each other and with other organisms, their effect on human beings, other animals and plants,etc.
Microbes include bacteria, fungi (yeasts and molds), protozoa, microscopic algae, and also viruses (the noncellular entities regarded as straddling the border between life and nonlife).
- Bacteria are unicellular organisms whose genetic material is not enclosed in a special nuclear membrane (hence called prokaryotes). Bacterial cells generally appear in shapes as Bacillus (rodlike), coccus (spherical or ovoid), and spiral (corkscrew or curved) are among the most common shapes, but some bacteria are starshaped or square. They may appear in pairs, chains, clusters, or other groupings.
- Fungi are eukaryotic organisms with cells that have a defined nucleus and rigid cell walls. Fungi may be unicellular (yeasts) or multicellular. The most typical fungi are molds that consists of mycelia, which are made up of long filaments called hyphae that branch and intertwine. Large multicellular fungi include mushrooms that may resemble plants, but they cannot carry out photosynthesis and are saprophytic or parasitic in nature.
- Protozoa are eukaryotic unicellular organisms that move by cilia, flagella or pseudopodia, and are usually parasitic (organisms that derive nutrients from living hosts) or free living in nature. Their size varies from 5-200 μm, they lack a rigid cell wall and are differentiated on the basis of morphological, nutritional and physiological characteristics. Protozoa are known to cause various diseases in human beings and animals.
- Algae are simple photosynthetic eukaryotes found most commonly in aquatic environments or in damp soil. They are unicellular to multicellular and either motile or nonmotile. Extensive algal growth in water bodies deteriorate the quality of the water releasing toxic chemicals into water bodies, or growing in swimming pools.
- Viruses are a distinctive group of acellular obligate intracellular parasites, very small in size, whose uniqueness resides in their simple, acellular organization with inimitable pattern of reproduction. A complete virus particle consists of one or more molecules of DNA or RNA enclosed in a coat of protein, and sometimes also in other complex layers that contain carbohydrates, lipids, and additional proteins
Microorganisms thrive in almost all types of environmental extremities in nature. Microorganisms are closely associated with our day to day lives in beneficial as well as detrimental ways. Fortunately most microorganisms are completely harmless to humans and only a very small fraction of the community belongs to the pathogenic group. Moreover, the bacteria are highly specific in nature as far as their pathogenecity towards a host is concerned.
Many microorganisms are known to cause mild or severe infectious and fatal diseases in humans and animals. Microorganisms also cause food spoilage, deterioration of materials such as wood, metal etc. However, they play a major role in making of various food products and beverages as yogurt, cheese, wine etc. Microorganisms also contribute towards the production of various antibiotics, and biomolecules as enzymes, vitamins that are used in medicinal and therapeutic purposes.
Points to Remember:
- Microbiology may be defined in terms of the size of the organisms studied and the techniques employed.
- Antony van Leeuwenhoek was the first person to describe microorganisms.
- 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.
- Size range of molds is 2.0-10 μm and yeast has size varying in the range of 5-10 μm.
- The cottony growths sometimes found on bread and fruit are mold mycelia.
- Prokaryotic cells differ from eukaryotic cells in lacking a membrane-delimited nucleus, and in other ways as well.