Traditionally, living organisms were divided into two major groups namely: the PLANTS making up the plant kingdom and ANIMALS constituting the Animal kingdom. But modern biology has differentiated them into three groups and the new group is the PROTISTA kingdom which are small microorganisms. The organisms of this new group consist of both plants and animals. This new method of classification divided Biology into three disciplines of Biological Sciences: Botany that studies the diversity, form and function of plants, Zoology that deals with the study of diversity, farm and function of animals while Microbiology studies the forms and function of microorganisms. All these disciplines study their respective living organisms as well as their interactions with their environments that could be biotic (living) or abiotic (nonliving) components.
The diversity, forms and functions of these living organisms are now well understood with the recent advances in cellular and molecular biology, cell and tissue culture and cloning with genetic engineering studies.
MICROORGANISMS OR MICROBES
Consist of some that are single-cell organisms (UNICELLULAR) while others are MULTICELLULAR organisms, and too small to be seen with the naked eye except with a MICROSCOPE. In some of the multicellular organisms, all the cells are alike while in others, the cells are differentiated to perform different functions as is found in higher algae and fungi. One thing common to microorganisms is that differentiation has not reached the extent found in higher organisms. Microorganisms include the following.
Virus
Bacterial (including actinomycetes)
Blue-green algae (Cyanobacteria)
Protozoa
Slime moulds
Fungi ( Yeast and moulds) and Algae.
MICROBES AND DISEASES
About a century ago, no one knew the real causes of diseases like cholera, yaws or leprosy. The connection between disease and microscopic organisms (microbes) was worked out by Louis Pasteur (1822-1895) in Dole, France. He proved that microorganisms caused chicken cholera and silkworm diseases even though these ideas were initially ridiculed. Pasteur Crushed and examined the bodies of healthy and diseased silk moths immediately they had laid their eggs. Within the cells of the diseased moths he saw tiny particles under themicroseope. He injected a healthy moth with fluid from the diseased moth's body, the healthy moth became sick. He also discovered that the illness was also contagious; The tiny particles which caused the disease were bacteria.
Robert Koch (1843-1910), a German physician also linked the microbes with diseases. his series of investigations revealed that human diseasessuch as anthrax and tuberculosis were caused by bacteria. He sdeed that the microorganisms were always found in the animals suffering from the diseases. Koch worked out how to remove ~ microbes from a diseased organism and culture (grow) them in agar, a jelly-like . Substance. He postulated rules to guide investigations into the cause of disease.
Koch 's postulates are as follows:
The same microbe must be found in every case of the disease that is studied.
When microbes are removed from a diseased Animal it must be possible to grow them in pure culture. A pure culture contains only one type of microorganism.
if microbes from the pure culture are given to a healthy animal, this animal must develope the disease.
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