Definition of Microbiology
It is a branch of science that deals with the study of microscopic forms of life these micro-organisms are less than 1 mm in size.
Characteristics of Micro-organisms
- These micro-organisms are very small in size generally less than 1 mm.
- They are not visible through our naked eyes.
- These organisms are either unicellular or multicellular.
- Prokaryotic or eukaryotic in nature.
- They may be motile or non motile.
- Micro-organisms are present everywhere in our surrounding like air, water,soil, dust and bodies of plants, animals and human beings.
Taxonomic Differentiation of Micro-organisms
- Protozoa are unicellular, eukaryotic in nature.
- They are parasitic or saprophytic.
- The size range of protozoa is generally 10 – 50 micrometer.
- These organisms generally exist in aqueous environment and soil.
- They show motility by flagella, cilia, or pseudopodia.
- Protozoa can absorbs their food material by cell membrane or by engulfing the food by phagocytosis.
- Some parasites are pathogenic in nature .They can reproduce sexually or asexually.
- Examples of protozoa: Amoeba, Paramecium, Euglena.
- Algae are eukaryotic, autotrophic, unicellular or multicellular organisms.
- Their size ranges from 1 micrometer to several feet.
- Algae are autotrophic in nature as it contain chlorophyll pigment for photosynthesis.
- It may be motile or non-motile in nature.
- Algal cells can produce sexually or asexually in nature.
- They are generally found in moist soil and aquatic environment.
- Examples of algae-Chlorophyta, Rhodophyta, Phaeophyta, Cyanophyta.
- Fungus are eukaryotic,autotrophic or heterotrophic.
- They are non-motile,unicellular or multicellular in nature.
- If fungus are unicellular in nature it is called as yeast and if it is multicellular it is differentiated into molds.
- Fungal cells may be saprophytic or parasitic.
- It contain septate or non-septate hyphae called as mycellium with a rigid cell-wall.
- Fungus and fungal spores are generally present in moist places,air,soil and dust.
- Examples of fungus-Mucor,Aspergillus.
- Bacteria are prokaryotic, unicellular micro-organisms. It size ranges from 1-2 micrometer.
- It may be cocci,rod or spiral shape.
- Bacteria reproduce by binary fission.
- They may be motile or non-motile in nature.
- Bacteria cointain a well defined cell wall .On the basis of cell-wall bacteria are classified into Gram-positive or Gram-negative bacteria.
- They may be autotrophic or hetertrophic in nature.
- Some bacteria are pathogenic in nature.
- Examples of bacteria: Staphylococcus aureus, E.coli, Streptococcus, Bacillus.
- Viruses are ultra-microscopic structure they are visible through electron microscope.
- They are obligate intracellular parasites their size is less than 0.2 micrometer.
- The genetic material is enclosed into a protien coat.
- It lacks cellular components which are necessary for multiplication it depends on its host for its multiplication.
- The genetic material may be RNA or DNA.
- Viruses multiply on living host.
- Examples of viruses– Herpus virus, HIV, TMV etc.