– Discovery
– Mahavira postulated the existence of microscopic creatures in the 6th century BC.
– Antonie van Leeuwenhoek was the first to study microscopic organisms.
– Lazzaro Spallanzani showed that boiling a broth stopped it from decaying.
– The Jains of India postulated the existence of tiny organisms called nigodas in the 6th century BC.
– Marcus Terentius Varro warned against locating a homestead near a swamp due to unseen creatures in the 1st century BC.
– Habitats
– Microorganisms can be found from poles to equator, deserts, geysers, rocks, and the deep sea.
– Some are adapted to extreme conditions like hot or cold environments.
– Deinococcus radiodurans thrives in high radiation environments.
– Microorganisms are present in the microbiota of all multicellular organisms.
– Evidence suggests 3.45-billion-year-old Australian rocks contained microorganisms.
– Importance
– Microbes are vital in fermenting foods, treating sewage, and producing fuel and enzymes.
– They are essential in biology as model organisms and have been used in biological warfare.
– Microbes are crucial in fertile soil and make up the human microbiota.
– Pathogens causing infectious diseases are microbes and are the target of hygiene measures.
– Microorganisms produce bioactive compounds and are important in human health.
– Diversity
– Microorganisms include most unicellular organisms from all three domains of life.
– Archaea and Bacteria domains solely consist of microorganisms.
– Eukaryota domain includes multicellular organisms and unicellular protists and protozoans.
– Some protists are related to animals and green plants.
– Micro-animals, fungi, and algae can be microscopic but are not always considered microorganisms.
– Applications
– Microorganisms are used to ferment foods, treat sewage, and produce bioactive compounds.
– They play a role in producing fuel and enzymes.
– Microbes are model organisms in biology and have applications in biological warfare.
– They are crucial in maintaining fertile soil and the human microbiota.
– Pathogens causing infectious diseases are microbes and are targeted by hygiene measures.
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.
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.[further explanation needed]
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.
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.