Microbiology is the study of microorganisms. The term microbiology derives its name from three Greek words mikros [small] bios [life] and logos [study].
Microorganisms are tiny living organisms that are too small to be seen with the naked eye. So, they can be looked into and studied only with the help of microscope. Small subcellular or cellular living beings with milli-micron or micron in size and are not visible to our naked eyes are called micro-organisms.
Earth formed 4.5 billion years ago. Within the next billion years, the first cellular life forms microbes appeared. Since that time, microorganisms have evolved and diversified to occupy virtually every habitat on Earth: from oceanic geothermal vents to the coldest Arctic ice.
The diversity of cellular microorganisms is best exemplified by their metabolic capabilities. Some carry out respiration, just as animals do. Others perform photosynthesis, rivaling plants in the amount of carbon dioxide they capture, forming organic matter and releasing oxygen into the atmosphere. Still other microbes are able to use inorganic molecules as sources of energy in both The Evolution of Microorganisms and Microbiology oxic (oxygen available) and anoxic (no oxygen) conditions. Microbes also are diverse in terms of environmental conditions. Some withstand extremes of temperature, pressure, and pH.
Indeed, studies have shown that some Earth microbes tolerate conditions that simulate those on Mars. These microbes are important for understanding what life might be like on other worlds.
The science of microbiology revolves around two interconnected themes: (1) understanding the nature and functioning of the microbial world, and (2) applying our understanding of the microbial world for the benefit of humankind and planet Earth.
As a basic biological science, microbiology uses microbial cells to probe the fundamental processes of life.
In so doing, microbiologists have developed a sophisticated understanding of the chemical and physical basis of life and have learned that all cells share much in common.
As an applied biological science, microbiology is at the forefront of many important breakthroughs in human and veterinary medicine, agriculture, and industry.
From infectious diseases to soil fertility to the fuel you put in your automobile, microorganisms affect the everyday lives of humans in both beneficial and detrimental ways.
Microorganisms existed on Earth for billions of years before plants and animals appeared, and we will see later that the genetic and physiological diversity of microbial life dwarfs that of the plants and animals.
Although microorganisms are the smallest forms of life, collectively they constitute the bulk of biomass on Earth and carry out many necessary chemical reactions for higher organisms.
In the absence of microorganisms, higher life forms would never have appeared and could not be sustained. Indeed, the very oxygen we breathe is the result of past microbial activity.
Moreover, humans, plants, and animals are intimately dependent on microbial activities for the recycling of key nutrients and for degrading organic matter.
It is thus safe to say that no other life forms are as important as microorganisms for the support and maintenance of life on Earth.
Micro-organisms are basically classified under the following 2 groups:
Prokaryotic microbes: These include subcellular living entities like prions, viroid, viruses and cellular organisms like bacteria, cyanobacteria etc.
Eukaryotic microbes: These include cellular microbe belonging to following groups: a. Algae. Ex: Chlamydomonas, Diatoms. b. Fungi. Ex: Yeast, Rhizopus. c. Protozoans. Ex: Plasmodium, Amoeba.
