Microbiology is the study of life forms that we need microscopes to see. At the microscopic level, our usual classification of life forms into either plants or animals breaks down and we have to resort to names such as microorganisms, bacteria, bugs, and microbes to describe these very tiny creatures.
While it is not clear who invented the microscope, it is known that instruments were being developed as early as the end of the sixteenth century. Several famous people contributed to improving early models and no doubt many saw things moving that they identified as simple life forms.
Antonie van Leeuwenhoek, 'the Father of Microbiology', a Dutch businessman and self-taught scientist, is credited with much pioneering work in designing and developing microscopes and in establishing microbiology as a scientific discipline in its own right.
On 17 September 1683, Leeuwenhoek wrote to the Royal Society in London regarding his observations on plaque that he scraped from between his own teeth. He described the structure of the plaque and went on to detail extremely tiny life forms that he could barely make out swimming in it. His own words describe his Eureka moment: 'I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving.'
His account of the little animalcules very prettily a-moving is the first recorded account of anyone ever seeing live bacteria. Advances in microscopy since Leeuwenhoek's time means that many thousands of bacteria are now named and are known in some detail. Leeuwenhoek discovered that the plaque on our teeth teems with bacteria. But there's more.
It is now known that the average person's gut hosts a complex community of bacteria. A typical community is composed of a minimum of some 200 different kinds of bacteria, perhaps up to 1,000 species. In terms of numbers, the total population can be as high as three trillion, that's 3,000,000,000,000 individuals. And though microscopic in size, their combined weight makes up about 2kg of the average person's body mass.
It would be very wrong to dismiss these tiny creatures as insignificant. As more ground-breaking research is carried out, it is becoming increasingly clear that the community of bacteria that we host in our intestines contributes significantly to our physical and mental health and wellbeing. And it is also becoming increasingly clear that it is a two-way process: we determine the structure of our bacterial community via our diet and lifestyle.