Microorganisms
Microorganisms are incredibly small organisms, often invisible to the naked eye, that inhabit nearly every environment on Earth, including the human body. They fall into two main categories: prokaryotic microorganisms, which include bacteria and archaea that lack a membrane-bound nucleus, and eukaryotic microorganisms, comprising unicellular and multicellular organisms like some fungi, protozoa, and algae that have a nucleus. The field of microbiology focuses on studying these organisms, which are crucial for public health, agriculture, and environmental sustainability.
Microorganisms have played a pivotal role in the history of life on Earth, emerging around four billion years ago and contributing to essential processes like oxygen production and nutrient cycling. While they are vital in various applications, such as food production and the development of antibiotics, they can also be pathogenic, causing diseases in plants and animals. Historically, the understanding of microorganisms advanced significantly with the invention of the microscope and discoveries made by scientists like Louis Pasteur. Today, microorganisms are manipulated in biotechnology to enhance food production and develop medicines, highlighting their importance in both ecological balance and human health.
Microorganisms
Microorganisms are very small organisms that generally cannot be seen without a microscope. These tiny organisms live everywhere, including within the human body. Microorganisms may be prokaryotic or eukaryotic. Prokaryotic microorganisms (or prokaryotes) include bacteria and archaea, which are single-celled organisms that lack a membrane-bound nucleus. Eukaryotic microorganisms (or eukaryotes) may be unicellular or multicellular and include some plants, animals, and fungi. Eukaryotic microorganisms have cells that contain a nucleus.
Microbiology is the branch of biology that studies microorganisms. The study of microorganisms is beneficial to public health, agriculture, and the environment. Microorganisms play an important role in human health. They also contribute to quality food production. Microbiologists study microorganisms such as bacteria to improve disease treatments, and biotechnology firms utilize microorganisms to develop products such as food and medicine.
Origin of Microorganisms
Microorganisms were the only forms of life on Earth for billions of years. Scientists believe they first appeared approximately four billion years ago. Archaeologists have uncovered fossils containing microbes that date back 3.5 billion years. Ancient microorganisms were self-reproducing life forms capable of existing in a dark, oxygen-free environment. Microbes eventually reacted with energy from the Sun and began producing oxygen through photosynthesis. Microorganisms played a crucial biological role in the development of advanced life on Earth. These organisms recycled organic matter, released oxygen into the atmosphere, and produced nitrate, the nitrogen source essential to all plants.
Microorganisms evolved over time, adapting to their environment and developing self-sustaining habits that eventually led to the formation of complex plant and animal life. These life forms had to develop early resistance to various microbial threats and eventually built an immune system and tough outer bodies to combat bacterial invasions. Plants and animals did not evolve to become resistant to all bacteria, however, which accounts for the presence of modern diseases.
History of Microbiology
People did not know microorganisms existed for thousands of years. Since microorganisms were not viewable to the naked eye, scientists could not study microorganisms before the development of the microscope. Dutch merchant Antoni van Leeuwenhoek first observed microorganisms in 1673. He used a self-designed microscope that magnified the organisms up to three hundred times their size. Van Leeuwenhoek observed only the structure of microorganisms, however. Scientists did not understand the purpose of microorganisms until the 1830s. German physiologist Theodor Schwann's discovery that alcohol production in beer and wine fermentation was dependent on yeast, a fungus, spearheaded a new interest in the role of microorganisms in nature.
In 1854, French scientist Louis Pasteur applied knowledge of yeasts to his study of wine fermentation. He found that certain bacteria spoiled wine, converting its sugars to lactic acid instead of alcohol. Pasteur also discovered that certain microorganisms were responsible for souring milk. He used this knowledge to develop pasteurization, a process that involved heating substances to kill bacteria. Modern dairy farmers continue to pasteurize their milk to produce quality dairy products. Pasteur also learned that successful fermentation relied on specific microorganisms and particular chemical conditions. He found that some microorganisms require oxygen to flourish while others require an oxygen-free environment. As Earth's atmosphere lacked oxygen in its earliest days, scientists believe microorganisms that do not require oxygen to reproduce developed from the oldest types of organisms on the planet.
Microbiologists quickly discovered that microorganisms are everywhere on Earth. These biological units are found in soil, air, and water. Microorganisms also are present in the food people eat and in human skin, mouths, noses, intestines, and other locations throughout the body.
Microorganism Functions
Prokaryotic microorganisms, which do not have a cell nucleus, consist of bacteria and archaea. Prokaryotic cyanobacteria, or blue-green algae, are believed to have developed from the most ancient microorganisms. These bacteria are important oxygen producers, and microbiologists consider them a chief predecessor of various plant structures, such as chloroplasts. Prokaryotic microorganisms make up the majority of organisms on Earth and can be found everywhere in the environment.
Though most eukaryotes are visible, multicellular organisms, some eukaryotic microorganisms do exist. Examples include microalgae, fungi, and protozoa. Green algae are important eukaryotic microorganisms and are a major source of food in the oceans, where all organisms lived until they evolved to dwell on land. Scientists believe plants evolved from green algae approximately 450 million years ago, around the same time that amphibians and land animals emerged. Microorganisms provided food for continuously evolving plants and animals for billions of years.
Recent developments in biotechnology have given microorganisms greater purpose than ever before. Biologists are capable of manipulating microorganisms to manufacture food and medications. Beer, wine, and cheese production all rely on the careful cultivation of microorganisms. Water treatment facilities also utilize microorganisms to purify water. Cultured microorganisms allow for the large-scale production of antibiotics. Of the eight thousand antibiotics available, most are made from penicillin, a mass-cultured microbial fungus.
Though microorganisms can be used to combat disease, they also have the ability to cause disease. Protozoa are the main cause of major diseases in animals, while fungi are responsible for the majority of all plant diseases.
Bibliography
Debre, Patrice. Louis Pasteur. Baltimore: JHU Press, 2000, 156. Print.
"Definition and Survey." Ullmann's Encyclopedia of Industrial Chemistry. 6th ed. Vol. 5. Weinheim, Germany: Wiley-VCH, 2003, 322. Print.
O'Hara, Ann M., and Fergus Shanahan. "The Gut Flora as a Forgotten Organ." The European Molecular Biology Organization. National Center for Biotechnology Information. July 2006. Web. 19 Dec. 2014. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1500832/
Hayward, Chris A. "Microorganisms." Encyclopedia of Life Sciences.Vol. 12. Chichester, UK: Wiley, 2005, 25–36. 19 Dec. 2014.
Pelczar, Rita M., and Michael J. Pelczar. "Microbiology." Britannica, 19 Sept. 2024, www.britannica.com/science/microbiology. Accessed 27 Nov. 2024.
Steinkraus, Keith H. "Microorganisms."Encyclopedia of Food and Culture. Ed. Solomon H. Katz. Vol. 2. New York: Charles Scribner's Sons, 2003, 507–513. 19 Dec. 2014.