Microbiology (meaning: Micro-Small, Bios-Life, Logy-Study)is simply defined as the study of microscopic organisms (including bacteria, fungi, algae, protozoa, viruses and prions) that are too small to be seen clearly with the naked eye. It is simply the scientific study of microorganisms. Microorganisms or microbes are organisms that are too small to be seen by an unaided eye; and they include bacteria, fungi, viruses, protozoa, and algae as aforementioned. Microbes thrive in an amazing diversity of habitats, and can be found in extremes of heat, cold, radiation, pressure, salinity, and acidity. They can often be found where no other life forms could exist due to their ubiquitous nature. Microorganisms are ubiquitous in nature, and this implies that they are found everywhere even in the body of man and animals. Microbiology encompasses the study of both microscopic organisms (i.e., invisible forms of life) and macroscopic organisms (i.e., visible forms of life) since some group of microbes (particularly some algae and fungi) can also exist in the macroscopic state in their natural environment. This specific feature of these organisms (i.e., some macroscopic microbes like fungi) allows them to be spotted in their natural habitat even without a microscope. The microscope is the number one tool for observing microorganisms in the laboratory or even in their natural habitat. Microbiology is also the study of microorganisms and their interaction with other living organisms including humans, plants and animals and the entire natural environment or ecosystem.


Microbiology is an experimental biological science that deals with invisible forms of life or microbes; and it employs a variety of microbiological techniques that includes but not limited to isolation technique, culturing (growing) technique, identification technique, staining technique and microscopical technique (microscopy) which allows microbiologists to study in detail the intricacies of microorganisms and how they relate with other organisms in their natural habitat or environment. Though the concept of microbiology is often synonymous with the study of bacteria (bacteriology); this experimental field of biological sciences also includes the study of fungi (mycology), algae (algology), viruses (virology), and protozoa (protozoology) as well as the study of other macro-organisms such as lichens, endophytes, mycorrhizae and mushrooms. Microorganisms as earlier said are organisms that are usually too small (less than 1 mm in diameter) to be seen by the naked eye. However, it is noteworthy that some macroscopic forms of organisms including some fungi (for example moulds), some unicellular protists, mushrooms and algae as earlier highlighted still exist, and are also studied in this field of microbiology. Microbiology is a fundamental biological science that focuses on small forms of life, and how these organisms can be understood and harnessed for the benefit of mankind, especially medically, industrially, agriculturally and economically.

As one of the fields of biological sciences and a fundamental aspect of the medical and biomedical sciences, the field of Microbiology (which has been in existence since mid 1600s) is a wide-ranging subject that includes immunology, virology, bacteriology, parasitology, mycology, serology, and algology. The above definition of microbiology may not be all encompassing due to the reality of the fact that some microorganisms are more often than not, larger and visible to the naked eyes. Some examples of microorganisms and/or macroorganisms which are large and seen by the naked eyes may include Rhizopus nigricans (thebread mould fungi), Thiomargarita namibiensis and Epulopiscium fishelsoni and some filamentous algae (for example blue-green algae). T. namibiensis(which measures about 100-750 µm in diameter) is a Gram-negative coccoid oceanic Proteobacterium that was discovered in Namibia, and it is a large bacterium that can be seen by the naked eyes. E. fishelsoni (which measures about 100-600 µm in diameter) is a Gram-positive bacterium that was discovered in the gut of fish (particularly the surgeonfish) from the red sea. These bacteria (i.e., T. namibiensis and E. fishelsoni) are currently the world’s giant (largest) bacteria which are usually bigger than the variety of known bacteria that usually measures about 0.3 µm or less than 1 mm in diameter such as Escherichia coli. Both T. namibiensis and E. fishelsoni are found in aquatic habitats especially in marine and/or freshwaters; and they may also be called marine microbes. Aside these two bacteria (i.e., T. namibiensis and E. fishelsoni), the vast majority of bacteria and other microbes are microscopic in nature and cannot be seen by the naked eye.

Microbiology is both an applied and basic biological science which deals with many important practical problems in agriculture, medicine, the soil, industry and the environment; and the knowledge of microbiology is also applied in the industry such as in food industry, biotechnology, brewery, medical industry and pharmaceutical industry where microbes are used to produce a variety of products and services that are beneficial to mankind, plants, the environment and other animals. The field of microbiology which is like the foundation of all the other biological sciences has enormous relevance in other fields such as biology, pharmacy, nursing, ecology, biotechnology, nanomedicine/nanotechnology, biochemistry, molecular biology, cytology, medicine and agriculture to mention but a few. Microbiology is the bedrock of medicine and other health-related disciplines because several of the infectious diseases and infections that negatively influence the human race as well as animals and plants are caused by some pathogenic microorganisms, which are the main subject of clinical microbiologists in the hospital. As an applied biological science, the knowledge of microbiology can be applied in a wide variety of human endeavours to improve the quality of life of man and animals and even improvement in crop production. And this is usually achieved by harnessing the metabolic capabilities of microorganisms towards the production of specific goods and services that are of immense economic benefit to man, animals, plants and the environment.

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of microorganisms. 12th edition. Pearson Benjamin Cummings Publishers. USA. Pp.795-796.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Prescott L.M., Harley J.P and Klein D.A (2005). Microbiology. 6th ed. McGraw Hill Publishers, USA. Pp. 296-299.

Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

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