Who among the following had discovered the ‘Bacteria’?

🔑Key Points:
-Antonie van Leeuwenhoek used single-lens microscopes, which he made, to make the first observations of bacteria and protozoa. 
-His extensive research on the growth of small animals such as fleas, mussels, and eels helped disprove the theory of spontaneous generation of life.
-Robert Hooke was an English scientist, architect, and polymath, who, using a microscope, was the first to visualize a micro-organism.
-Louis Pasteur was a French biologist, microbiologist, and chemist renowned for his discoveries of the principles of vaccination, microbial fermentation, and pasteurization.
-Rudolf Ludwig Carl Virchow was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as 'the father of modern pathology' and as the founder of social medicine, and to his colleagues, the 'Pope of medicine'.

🔴Additional Information:
-Bacteria is a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Usually a few micrometres in length, bacteria have many shapes ranging from shapes to rods and spirals.
-In humans and most animals, the largest number of bacteria exist in the gut, and a large number on the skin. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial, particularly in the gut flora.