Microbiology is the study of microorganisms or microbes, a diverse group of usually tiny simple life forms that include bacteria, archaea, algae, fungi, protozoa, and viruses. The field deals with the structure, function, and classification of such organisms and with ways to exploit and control their activities. The discovery in the 17th century of living forms that exist invisible to the naked eye was a significant milestone in the history of science, since from the 13th century onward it had been postulated that “invisible” entities were responsible for decomposition and destruction. disease. The word microbe was coined in the last quarter of the 19th century to describe these organisms, all of which were thought to be related.
As microbiology eventually became a specialized science, microbes were found to be a very large group of extremely diverse organisms. Daily life is inextricably interwoven with microorganisms. In addition to populating the internal and external surfaces of the human body, microbes abound in the soil, the seas and the air. Abundant, though generally unnoticed, microorganisms provide ample evidence of their presence, sometimes unfavourably, as when they cause spoilage of materials or spread disease, and sometimes favourably, as when they ferment sugar in wine and beer, make bread rise, flavour cheeses, and produce valuable products like antibiotics and insulin. Microorganisms are invaluable to the Earth’s ecology, breaking down animal and plant remains into simpler substances that can be recycled into other organisms.
Microbiology essentially began with the development of the microscope. Although others may have seen microbes before him, it was Antonie van Leeuwenhoek, a Dutch clothier whose hobby was lens polishing and microscope making, who was the first to provide proper documentation of his observations. His descriptions and drawings included protozoa from animal entrails and bacteria from tooth scrapings. His records were excellent because he produced magnifying lenses of exceptional quality. Leeuwenhoek reported his findings in a series of letters to the British Royal Society in the mid-1670s.
Although his observations aroused much interest, no one made a serious attempt to repeat or expand on them. Leeuwenhoek’s “animalcules,” as he called them, remained mere oddities of nature to scientists of his day, and enthusiasm for the study of microbes slowly grew. It was only later, during the 18th-century revival of a long-standing controversy over whether life could develop from non-living material, that the importance of microorganisms in the scheme of nature and in the health and well-being of microorganisms became apparent in the welfare of humans.
Spontaneous versus biotic generation of life
The early Greeks believed that living things could originate from non-living matter (abiogenesis) and that the goddess Gaia could create life from stones. Aristotle discarded this notion but still held that animals could arise spontaneously from different organisms or from the ground. His influence on this concept of spontaneous generation was still felt as late as the 17th century, but toward the end of that century, a chain of observations, experiments, and arguments began that finally disproved the idea.
This breakthrough in understanding was hard-fought and involved a series of events, with the forces of personality and individual will often obscuring the facts. Although Francesco Redi, an Italian physician, disproved in 1668 that higher forms of life could arise spontaneously, proponents of the concept claimed that microbes were different, and in fact arose this way. Illustrious names such as John Needham and Lazzaro Spallanzani were adversaries in this debate in the mid-eighteenth century. In the early 1800s, Franz Schulze and Theodor Schwann were major figures in trying to disprove theories of abiogenesis until Louis Pasteur finally announced the results of his conclusive experiments in 1864.
In a series of masterful experiments, Pasteur demonstrated that only pre-existing theories of microbes could give rise to other microbes (biogenesis). Modern and precise knowledge of the forms of bacteria can be attributed to the German botanist Ferdinand Cohn, whose main results were published between 1853 and 1892. Cohn’s classification of bacteria, published in 1872 and extended in 1875, dominated the study of these organisms since then.
Microbes and diseases
Girolamo Fracastoro, an Italian scholar, advanced the notion as early as the mid-16th century that contagion is an infection that passes from one thing to another. A precise description of what is transmitted eluded discovery until the late 1800s, when the work of many scientists, including Pasteur, determined the role of bacteria in fermentation and disease. Robert Koch, a German physician, defined the procedure (Koch’s postulates) to prove that a specific organism causes a specific disease.
The foundations of microbiology were securely laid during the period between 1880 and 1900. Students of Pasteur, Koch, and others discovered in rapid succession a large number of bacteria capable of causing specific diseases (pathogens). They also developed an extensive arsenal of laboratory techniques and procedures to reveal the ubiquity, diversity, and abilities of microbes.
Progress in the 20th century
All of these developments occurred in Europe. It was not until the early 20th century that microbiology became established in the United States. Many microbiologists working in the United States at the time had studied with Koch or at the Pasteur Institute in Paris. Once established in America, microbiology flourished, especially with regard to related disciplines such as biochemistry and genetics. In 1923, American bacteriologist David Bergey established that science’s primary reference, updated editions of which continue to be used today.
Since the 1940s, microbiology has experienced an extremely productive period during which many disease-causing microbes have been identified and methods have been developed to control them. Microorganisms have also been used effectively in the industry; their activities have been channelled to the point where valuable products are now vital and common.
The study of microorganisms has also advanced in the knowledge of all living beings. Microbes are easy to work with and therefore provide a simple vehicle for studying the complex processes of life; as such, they have become a powerful tool for studies of genetics and metabolism at the molecular level. This intense probing of the functions of microbes has yielded numerous and often unexpected dividends. Knowledge of the basic metabolism and nutritional requirements of a pathogen, for example, often leads to a means of controlling disease or infection.