Introduction

There are more bacteria than any species, and they are omnipresent.
Bacteria are classifies as prokaryotes, single celled organisms too small to be seen with naked eye. Bacteria have no nucleus hold their DNA as eukaryotes do.
Although Bacteria are seem to cause diseases , but most of them actually do not. Those that actually do cause diseases have been greatly reduced in their seriousness by the invention of antibiotics, but overuse of these antibiotics have created antibiotic-resistant bacteria.
Anton Van Leeuwenhoek first saw bacteria though a microscope in 1676 and called them animalcules. It was Christian Gottfried Ehrenberg who came up with the term Bacteriam, meaning small staff. Agostino Bassi, in 1835, proposed the germ theory of disease, which knew that there was a connection between spread of disease and unseen organisms. Louis Pastuer and John Tyndall showed how bacteria only growa when exposed to air. Then in 1875, Robert Koch showed how anthrax was cause by bacteria.
There are many different shapes of bacteria, including coccus, bacillus, and sprillum. They increase in number by binary fission and the colonies may be circular, irregular, or branching. Bacteria also break down sugars using enzymes, this process being fermentation. Some might require oxygen, which are called aerobes, others might survive only in conditions where there is no oxygen, which are called anaerobes, and some might grwo on both of these conditions, which are called facultative anaerobes.
In 1928, Alexander Fleming discovered penicillin, and many antibiotics have been discovered to help humans.They can be two things: bactericidal or bacteriostatic.