Life

Bacteria, diseases and antibiotics

Not all bacteria are useful or harmless; some of them transmit diseases, even very serious ones, that especially in the past caused great epidemics. The bacterial origin of some pathologies, such as the plague, cholera, pneumonia or meningitis, has been only recently discovered. In the past, when the existence of bacteria was not known, these diseases were thought to be caused by sorcery, curses or the influence of the stars. The discovery of the existence of pathogenic micro-organisms led research to find ways to fight them. In 1929, Alexander Fleming, a Scottish doctor who conducted researches at St. Mary's Hospital in London, discovered penicillin: the very first antibiotic substance ever known and studied. Penicillin was discovered by chance during some research on staphylococci. Fleming prepared some containers (plates) where he grew colonies of this micro-organism. To be observed, the plates had to be opened, exposing the bacterial cultures to the air, letting other micro-organisms in. So, some mildews started growing amongst the colonies of staphylococci. The scientist noticed that around the mildew the colonies grew more and more transparent until they disappeared, so he assumed that the mildew produced a substance that could wipe out the bacteria. Fleming extensively studied this substance and, since it was produced by the mildews of the genus Penicillium, he called it penicillin. The discovery of antibiotics has eradicated or remarkably reduced very many of the most dangerous diseases. But defeating bacteria is no easy feat. These micro-organisms can generate resistant strains, i.e. genetic variants that spontaneously evolve from one species and can survive even in the presence of antibiotic substances. This is why research must keep developing new antibiotics.