Ferdinand Julius Cohn Biography (1828-1898)

bacteriologist, plant pathologist

Cohn, the first scientist to define and systematically classify bacteria, isconsidered a founder of modern bacteriology. He is also noteworthy for providing critical support to others in the fledgling science, including the NobelPrize-winning Robert Koch.

Born to Jewish parents in 1828 in the Prussian city of Breslau (now Wroclaw,Poland), Cohn was a child prodigy reportedly able to read and write before his second birthday. He was admitted to the University of Breslau at the age of14, but because of anti-Semitic feelings in Prussia, he was never granted adegree there even though he successfully undertook four years of studies.

Instead, Cohn completed his studies at the University of Berlin, where he studied under the prominent physiologist Johannes Peter Müller. When revolution swept Europe in 1848, Cohn kept his liberal tendencies to himself and kept involved in his studies. In September, 1849, he wrote a rather anguished entry in his journal: "Germany dead; France dead; Italy dead; Hungary dead; only cholera and court-martials immortal. I have retired from this unfriendly outside world, buried myself in my books and studies; seeing few people, learning much, only inspired by nature." That year, Cohn's immersion in serious study was awarded with a doctorate in botanical studies.

However, continued anti-Semitism and Cohn's liberal politics forced him backto the University of Breslau, where he was allowed to work in the Physiological Institute, and in 1859 became professor of botany.

Cohn's initial research interests were simple forms of plant life: algae andfungi. However, over time his fascination with plant diseases evolved into aninterest in bacteria. He noticed that both plant and animal cells consist ofprotoplasmic material that is essentially identical, and was the first to state that bacteria are plants, not animals, as previously considered.

In 1872, Cohn published Researches on Bacteria, a landmark, three-volume treatise that contained the first systematic classification of bacteria. Cohn identified the six classes of bacteria: Bacillus, Bacterium, Micrococcus, Spirillium, Spirochaete and Vibrio. He discovered spores, tinyreproductive bodies produced by plants and bacteria, which Cohn identified as living bridges between the plant and animal worlds. Another important observation was that bacteria were capable of surviving high temperatures.

Cohn's work, combined with other discoveries by Louis Pasteur and theEnglish physicist John Tyndall eventually discredited the theory of spontaneous generation, which held that living organisms could develop from nonlivingmatter.

In an 1873 publication, Bacteria, the Smallest of Living Organisms, Cohn dramatically stated that bacteria "rule with demoniacal power over the weal and woe, and even over the life and death of man." It was highly likely, hesaid, that "already identified bacteria are in many diseases the conveyors and originators of infection, that they are the ferment of contagion . . .We have the firm conviction that to a more thorough and clearer knowledge of these facts will be joined the discovery of new methods by which to encounter thefearful enemy with better success than hitherto," Cohn accurately predicted.

In addition to his other accomplishments, Cohn established the world's firstplant physiology institute at Breslau in 1866. He also founded a journal, Contributions on Plant Biology, that chronicled the earliest years of modern bacteriology.

One of his greatest contributions to science, however, was an indirect one. In 1876, an unknown rural doctor named Robert Koch came to Cohn, convinced hehad discovered the cause of anthrax, a livestock disease that can be transmitted to humans, causing pneumonia and skin ulcers. Cohn recognized Koch's workas authoritative. He published the discovery in his new journal and introduced the country physician to the scientific research community. With support from Cohn, Koch went on to discover the bacterial causes for cholera and tuberculosis, receiving the Nobel Prize in 1905.

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