Courtesy : Bachelor of Science Microbiology (CBM) – Chemistry, Botany, Microbiology University

A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells.

The possible existence of unseen microbial life was suspected from ancient times, such as in Jain scriptures from sixth century BC India. The scientific study of microorganisms began with their observation under the microscope in the 1670s by Anton van Leeuwenhoek. In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In the 1880s, Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera, diphtheria, and anthrax. # ISO certification in India

Because microorganisms include most unicellular organisms from all three domains of life they can be extremely diverse. Two of the three domains, Archaea and Bacteria, only contain microorganisms. The third domain Eukaryota includes all multicellular organisms as well as many unicellular protists and protozoans that are microbes. Some protists are related to animals and some to green plants. There are also many multicellular organisms that are microscopic, namely micro-animals, some fungi, and some algae, but these are generally not considered microorganisms. # ISO certification in India

Microorganisms can have very different habitats, and live everywhere from the poles to the equator, deserts, geysers, rocks, and the deep sea. Some are adapted to extremes such as very hot or very cold conditions, others to high pressure, and a few, such as Deinococcus radiodurans, to high radiation environments. Microorganisms also make up the microbiota found in and on all multicellular organisms. There is evidence that 3.45-billion-year-old Australian rocks once contained microorganisms, the earliest direct evidence of life on Earth. # ISO certification in India

Microbes are important in human culture and health in many ways, serving to ferment foods and treat sewage, and to produce fuel, enzymes, and other bioactive compounds. Microbes are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. Microbes are a vital component of fertile soil. In the human body, microorganisms make up the human microbiota, including the essential gut flora. The pathogens responsible for many infectious diseases are microbes and, as such, are the target of hygiene measures. # ISO certification in India

Discovery

See also: History of biology and Microbiology § History

Antonie van Leeuwenhoek was the first to study microscopic organisms.

Lazzaro Spallanzani showed that boiling a broth stopped it from decaying.

Ancient precursors

Vardhmana Mahavira postulated the existence of microscopic creatures in the sixth century BC.

The possible existence of microscopic organisms was discussed for many centuries before their discovery in the seventeenth century. By the sixth century BC, the Jains of present-day India postulated the existence of tiny organisms called nigodas. These nigodas are said to be born in clusters; they live everywhere, including the bodies of plants, animals, and people; and their life lasts only for a fraction of a second. According to the Jain leader Mahavira, the humans destroy these nigodas on a massive scale, when they eat, breathe, sit, and move. Many modern Jains assert that Mahavira’s teachings presage the existence of microorganisms as discovered by modern science. # ISO certification in India

The earliest mention of micro organisms is found in hindu scriptures like the Atharvaveda, compiled 1200 BCE-1000 BCE, where Rishi Kanva refers to the microbes as Kirmis. He, along with his descendants Yamadagnni and Agasti, composed mantra suktas which highlight microbial infections and possible ways to cure them.

Rishi Agastya composed a mantra in Rig Veda which refers to two types of harmful creatures for ones body. The first being visible and second being so minuscule that they are invisible to the naked eyes.

The Shanti Parva of Ved Vyas Mahabharata mentions organisms that are so minuscule that they can’t be seen with naked eyes but only inferred.

There are many creatures that are so minute that their existence can only be inferred. With the failing of the eyelids alone, they are destroyed.

The earliest known idea to indicate the possibility of diseases spreading by yet unseen organisms was that of the Roman scholar Marcus Terentius Varro in a first-century BC book entitled On Agriculture in which he called the unseen creatures animalcules, and warns against locating a homestead near a swamp:

… and because there are bred certain minute creatures that cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and they cause serious diseases. # ISO certification in India

In The Canon of Medicine (1020), Avicenna suggested that tuberculosis and other diseases might be contagious.