The Golden Age of Microbiology

Rapid advances in the science of microbiology were made between 1857 and 1914.

Fermentation and Pasteurization

Pasteur found that yeast ferments sugars to alcohol and that bacteria can oxidize the alcohol to acetic acid.

He also developed a heating process (called pasteurization) that is used to kill bacteria in some alcoholic beverages and milk without altering their flavor.

The Germ Theory of Disease

In 1865 Louis Pasteur was hired to figure out what to do about silkworm disease. He was aware that in 1835 Agostino Bassi had shown a causal relationship between a fungus and the disease, so he looked for a connection with a microorganism. He discovered a protozoan was the causative agent and added more data to support the idea that microorganisms cause disease.

Joseph Lister introduced the use of a disinfectant to clean surgical dressings in order to control infections in humans (1860s). His reasoning:

• He knew about the link between microorganisms and animal diseases that was suggested by Pasteur's work.
  
• He knew about the work of Ignaz Semmelweis, who, in 1848, showed that puerperal fever was transmitted to patients by medical students, who didn't wash their hands between dissecting cadavers in anatomy lab and delivering babies.

Robert Koch proved that microorganisms caused disease. He used a sequence of procedures called Koch’s postulates (1876), which are used today to prove that a particular microorganism causes a particular disease.

Vaccination

In a vaccination, immunity (resistance to a particular disease) is conferred by inoculation with a vaccine.

In 1798, Edward Jenner demonstrated that inoculation with cowpox material provides humans with immunity from smallpox . Jenner claimed credit for the whole small pox/cow pox vaccination idea (even though he didn't call it vaccination at the time and the Chinese had been snorting powdered small pox scabs to generate immunity for hundreds of years prior to that). He still didn't have a clue what caused the disease, but prevention seemed like a pretty good breakthrough.

About 1880, Pasteur discovered that avirulent bacteria could be used as a vaccine for fowl cholera; he coined the word vaccine.

Modern vaccines are prepared from living avirulent microorganisms or killed pathogens, from isolated components of pathogens, and by recombinant DNA techniques.

The Birth of Modern Chemotherapy: Dreams of a “Magic Bullet”

Chemotherapy is the chemical treatment of a disease.

Two types of chemotherapeutic agents are synthetic drugs (chemically prepared in the laboratory) and antibiotics (substances produced naturally by bacteria and fungi that inhibit the growth of other microorganisms.

Paul Ehrlich introduced an arsenic-containing chemical called salvarsan to treat syphilis (1910).

Alexander Fleming observed that the mold (fungus) Penicillium inhibited the growth of a bacterial culture. He named the active ingredient penicillin (1928).

Chain and Florey, of Oxford University, purified penicillin and conducted clinical trials. Penicillin has been used clinically as an antibiotic since the 1940s.

In 1939, Rene Dubous discovered two antibiotics produced by the bacterium Bacillus.

Researchers are tackling the problem of drug-resistant microbes.

Summary