5 microorganisms that changed the world

International Microorganism Day

Microorganisms have changed the world and continuously influence it; they directly impact the Earth and its habitability, and indirectly regulate the way we live, act and think.

For this reason, for International Microorganism Day, we decided to collect the story of 5 microorganisms that have changed the world.

Streptococcus pyogenes and the CRISPR/Cas9 system

The CRISPR/Cas system was first studied in Escherichia coli and is used by bacteria to protect themselves from viral infections. The discovery of CRISPR changed the world of gene editing by making it possible to make specific modifications to the genome of animal, human and plant cells. 

To Streptococcus pyogenes we owe the discovery of one of the most widely used “molecular scissors”: Cas9, a nuclease perfectly capable of introducing genetic modifications into a wide variety of cells and organisms. Examples of applications include the development of pathogen-resistant varieties of agricultural plants, control of the spread of malaria, resistance by animals to diseases of viral origin, but also clinical diagnosis and research on cancer, infectious and genetic diseases.

Penicillium chrysogenum and the Penicillin

In 1928 bacteriologist Alexander Fleming observed the fact that some colonies of the bacterium Staphylococcus aureus failed to grow where the culture had been in contact with Penicillium notatum. He isolated the mold and found that it produced a substance that could kill many bacteria harmful to humans. Later, in 1939, a team of scientists at Oxford University, led by Howard Florey, developed a method to cultivate the mold by extracting and purifying penicillin. By 1945, penicillin became widely available, and thanks to scientist Dorothy Hodgkin, its chemical structure was determined, allowing the development of semisynthetic penicillins.

The development of penicillin not only enabled a number of medical practices impossible without its use but paved the way for the discovery of a number of new antibiotic drugs still used today to treat a variety of diseases.

Thermus aquaticus and the PCR

In the early 1960s, researchers began to show interest in extremophilic bacteria, microorganisms capable of living in conditions considered “non-canonical.” In 1969, through studies conducted in hot springs in Yellowstone National Park, a new species was described: Thermus aquaticus. The “extreme” microorganism aroused the interest of biochemists to search for thermostable enzymes and, in 1976, the Taq enzyme was isolated, which made possible, a few years later, the development of a technique that became a milestone of the scientific world: the famous and indispensable PCR.

Cyanobacteria and the Great Oxidation Event

Today we know an absolutely different atmosphere from the one that characterized the Earth before the Great Oxidation Event, the crisis which radically changed the environment. In this context, cyanobacteria, numerous inhabitants of the oceans, played a crucial role as producers of oxygen as a byproduct of photosynthesis. The oxygen then produced began to react with methane, producing carbon dioxide while, simultaneously, cyanobacteria continued to sequester CO2 and release oxygen. This phenomenon drastically reduced temperatures, and the Earth entered the first ice age. Although the scientific community still questions the causes and forces that moved the profound “climate crisis”, what is certain is that without the Great Oxidation Event the Earth and life on it would have been profoundly and radically different.

Leuconostoc, fermented foods and wine.

In 1878, scientist Philippe van Tieghem first described Leuconostoc mesenteroides, the main species of Leuconostoc, a genus of bacteria capable of heterolactic fermentation, a metabolic pathway in which carbohydrates are converted to lactic acid, alcohols, carbon dioxide and other products. Species of the genus Leuconostoc are used for the production of fermented foods such as dairy products (along with Lactococcus, Streptococcus and Lactobacillus spp.), fermented vegetables and cereals. In addition, some species are responsible for malolactic fermentation in wine. In our view, a world without fermented foods and wine would have been absolutely different (and perhaps a little sadder).

Sources

• Fuguo Jiang and Jennifer A. Doudna; “CRISPR–Cas9 Structures and Mechanisms”, 2017
• Jennifer A. Doudna and Emmanuelle Charpentier; “The new frontier of genome engineering with CRISPR-Cas9”, 2014
• D. Hsu et al.; “Development and Applications of CRISPR-Cas9 for Genome Engineering”, 2014
• Robert Gaynes; “The Discovery of Penicillin—New Insights After More Than 75 Years of Clinical Use”, 2017
• T. D. Brock; “The Value of Basic Research: Discovery of Thermus Aquaticus and Other Extreme Thermophiles”, 1997
• E. Schirrmeister et al.; “Cyanobacteria and the Great Oxidation Event: evidence from genes and fossils”, 2015
• Patricia Sánchez-Baracaldo and Tanai Cardona; “On the origin of oxygenic photosynthesis and Cyanobacteria”, 2019
• Denis Hemme and Catherine Foucaud-Scheunemann; “Leuconostoc, characteristics, use in dairy technology and prospects in functional foods”, 2003