Antonie van Leeuwenhoek: the father of Microbiology
We owe the discovery of bacteria to Antonie van Leeuwenhoek, "the Father of Microbiology".
Van Leeuwenhoek’s life is a great a scientific rags to riches story. Born in Delft, Holland, in 1632, he came from a family of basket makers and would end up as a fabric merchant. He received no higher education and spoke no language but Dutch. The latter, in particular, would have excluded him from the science of his time; most scientific texts were written in Latin or German. However freedom from the contemporary scientific dogma coupled to an insatiable curiosity proved to be a dynamite combination. Not only did he discover bacteria (what he called “animalcules”), he also discovered, among many other things, blood cells, sperm cells and microscopic nematodes (worms).
One of the original explorers of the microscopic world, van Leeuwenhoek used homemade microscopes to investigate the world around him. All microscopes at the time were largely homemade but he was particularly good at grinding lenses. Essentially, using no more than extremely powerful magnifying glasses (single lens microscopes) he could magnify objects up to two hundred times. His contemporaries could only magnify things twenty to thirty times despite using more technically advanced compound microscopes. This gave him a monopoly on early microscopic discoveries - much to the envy of his contemporaries.
Letters to the Royal Society
In 1673, he began writing to the recently-formed Royal Society (in London), where he described what he saw. Despite never actually writing a proper scientific paper, his work was very well regarded. Indeed, his work was considered so important that Henry Oldenburg learnt Dutch just to be able to translate it. van Leeuwenhoek also gained fame outside the scientific community: many visitors came to see the curious things he was describing. He even demonstrated circulation in an eel to Tsar Pete the Great of Russia in 1698.
Microscope to space station and microbiome
Science has moved on a great deal since 1683. We not only know what bacteria are, we can see inside them and understand how they work. Although structurally diverse; nearly all bacteria have a single piece of circular DNA. We have found them in nearly every habitat on earth. They have even been able to survive space in the International Space Station. Of course, no list of bacterial habitats would be complete without the human body. So significant are these bacteria that we have a name for them (microflora) and their genetics (microbiome), and a branch of science dedicated to understanding them.