Contributions by Louis Pasteur, Robert Koch, Sergei N. Winogradsky and Martinus W. Beijerinck

Louis Pasteur (1822–1895)

Pasteur is known as the father of microbiology and immunology

·               In 1849 Pasteur observed that Tartaric acid and racemic acid found in sediment of fermenting wine have identical chemical composition.  Upon intense inspection using a microscope, Pasteur noticed that these identical molecules have different spatial arrangement. One was the mirror image of the other.  This discovery led to the branch of science known as ‘stereochemistry’.

·               Until the second half of the 19^th century, Many scientists and philosophers believed in Spontaneous Generation -           Life could arise spontaneously from nonliving matter. Louis Pasteur disproved Spontaneous Generation - proved that all life comes from preexisting life.  Pasteur demonstrated that in sterilized and sealed flasks no life forms develops and in sterilized but open flasks microbes could grow.  Microorganism from air contaminate sterile solutions, but air itself does not create microbes.

·               His studies showed that living cells, yeast, are responsible for forming alcohol from sugar and contaminating microorganisms make the fermentation sour

·               To prevent contamination, Pasteur heated wine to 50–60 °C a process now known as pasteurization. It is used for the preservation of many foods and beverages, particularly milk

·               Pebrine, or "pepper disease," a disease of silkworms, caused by protozoa, mainly Nosema bombycis and other species.   The silkworm larvae having pebrine are covered in brown dots and are unable to spin thread.  Louis Pasteur identified the cause and developed a method called ‘graining’ when a plague of the disease spread across France.  Graining enabled elimination of contaminated females and the preservation of healthy eggs.  This technique was adopted by silk producers throughout the world.

·               Pasteur identified that the fermentation process could be arrested by passing air (oxygen) through the fermenting fluid - known today as the Pasteur effect.  He concluded that this is due to a microorganism that could ferment only in the absence of oxygen.  He introduced the terms aerobic and anaerobic to designate organisms that live in the presence or absence of oxygen

·               In 1879, Pasteur worked with the disease fowl cholera, or chicken cholera which was rampant in chicken coops at the time. When inoculated into a chicken, the bacteria kill the bird - Pasteurella multocida.  Pasteur used a weakened culture of bacteria to inoculate chickens which resulted in immune birds and thus the principle of vaccination with attenuated pathogens was discovered.

·               In 1879 Pasteur worked with the disease Anthrax caused by Bacillus anthracis.  Anthrax is an infectious disease that affects cattle, sheep, etc that can be transmitted to man.  It was responsible for killing large populations of sheep in France, detrimental to the economy.  Pasteur developed a mild, harmless culture of anthrax bacteria. Used this culture to vaccinate hundreds of livestock, and they became immune to the disease. 

·               In anthrax or chicken cholera vaccination the causative agents are artificially weakened or attenuated to immunize the animals Pasteur gave these artificially weakened diseases the generic name of "vaccines", in honour of Jenner's discovery

·               In 1882, Pasteur worked with an epizootic of Swine erysipelas and he developed a vaccine against this bacterial infection.

·               He carefully studied and discovered several other infectious diseases such as those caused by staphylococcus, streptococcus and pneumococcus.

·               Pasteur then worked with rabies.  Rabies is a highly contagious, infectious viral disease that attacks the central nervous system, transmitted via the bite of rabid animals.  On 1885, Pasteur administered his rabies vaccine on Joseph Meister, a young man bitten by a rabid dog and saved his life.  To help treat future cases of rabies, the Pasteur Institute was established in 1888 with monetary donations coming from all over the world.

·               His medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine.  Although Pasteur was not the first to propose the germ theory, his experiments indicated its correctness.  He is regarded as one of the three main founders of bacteriology, together with Ferdinand Cohn and Robert Koch

His few quotes

Chance favors the prepared mind.

Little science takes you away from God but more of it takes you to Him.

Gentlemen, it is the microbes who will have the last word.

The role of the infinitely small in nature is infinitely great.

It is not the germs we need worry about. It is our inner terrain.

 

Robert Koch (1843–1910)

The first direct demonstration of the role of bacteria in causing disease came from the study of anthrax by the German physician Koch

·               He proved causal relationship between a microorganism and a specific disease known as Koch’s postulates in 1884 and can be summarized as follows:

1.         The microorganism must be present in every case of the disease but absent from healthy organisms.

2.         The suspected microorganism must be isolated and grown in a pure culture.

3.         The same disease must result when the isolated microorganism is inoculated into a healthy host.

4.         The same microorganism must be isolated again from the diseased host.

·               He identified the specific causative agents of tuberculosis, cholera, and anthrax.  Robert Koch discovered the causative agent of Anthrax to be Bacillus anthracis.  He reported the causative agent of the disease tuberculosis to be the slow-growing Mycobacterium tuberculosis.  Koch studied cholera in Egypt and in India and identified the causative agent of cholera to be Vibrio cholerae.

·               Koch observed the phenomenon of acquired immunity while studying Plasmodium parasites, the cause of malaria

·               Koch cultured bacteria on the sterile surfaces of cut, boiled potatoes, but without success and tried to solidify regular liquid media by adding gelatin. Gelatin was not an ideal solidifying agent because it was digested by many bacteria and melted when the temperature rose above 28°C. Fannie Hesse, the wife of Walther Hesse, one of Koch’s assistants suggested the use of agar as a solidifying agent. Agar was not attacked by most bacteria and did not melt until reaching a temperature of 100°C.

·               One of Koch’s assistants, Richard Petri, developed the petri dish (plate), a container for solid culture media. These developments made possible the isolation of pure cultures that contained only one type of bacterium.

·               Koch also developed media suitable for growing bacteria with meat extracts and protein digests as nutrient sources and resulted in the development of nutrient broth and nutrient agar.

For his research on tuberculosis, Koch received the Nobel Prize in Physiology or Medicine in 1905. The Robert Koch Institute which monitors public health is named in his honor and is located in Berlin and Wernigerode

 

Sergei N. Winogradsky (1856–1953)

The Russian microbiologist Sergei N. Winogradsky made many contributions to soil microbiology.

·               He discovered that soil bacteria could oxidize iron, sulfur, and ammonia to obtain energy, and that many bacteria could incorporate CO2 into organic matter much like photosynthetic organisms do. This is chemoautotrophy or chemosynthesis, the process by which organisms derive energy from a number of different inorganic compounds.

·               Winogradsky also isolated anaerobic nitrogen-fixing soil bacteria and studied the decomposition of cellulose.

·               Winogradsky discovered the first known form of lithotrophy (using inorganic substrate to obtain energy via aerobic or anaerobic respiration) during his research with Beggiatoa in 1887. He reported that Beggiatoa oxidized hydrogen sulfide (H2S) as an energy source and formed intracellular sulfur droplets.

·               The Winogradsky column remains an important display of chemoautotrophy and microbial ecology.  This is a simple device for culturing a large diversity of microorganisms.  the device is a column of pond mud and water mixed with a carbon source such as newspaper (containing cellulose), egg-shells (containing calcium carbonate), and a sulfur source such as gypsum (calcium sulfate) or egg yolk. Incubating the column in sunlight for months will results in an aerobic/anaerobic gradient as well as a sulfide gradient and promote the growth of different microorganisms such as bacteria, cyanobacteria, and algae.

 

Martinus W. Beijerinck (1851–1931)

Martinus W. Beijerinck made fundamental contributions to microbial ecology. He is often considered one of the founders of virology and environmental microbiology.

·               He isolated the aerobic nitrogen fixing bacterium Azotobacter; a root nodule bacterium also capable of fixing nitrogen (Rhizobium); and sulfate reducing bacteria.

·               Beijerinck proved that a virus causes the tobacco mosaic disease

·               Beijerinck invented the enrichment culture, a fundamental method of studying microbes from the environment.

·               Beijerinckia (a genus of bacteria), Beijerinckiaceae (a family of Rhizobiales), and Beijerinck (crater in moon) are named after him.