Ferdinand Julius Cohen, born into the Jewish community of Breslau in the 19th century, was a pioneer of modern microbiology. His studies of bacteria, spores, and sterile cultures helped lay the foundation for the work of Pasteur and Koch and the transition from hypotheses about spontaneous generation to a scientific understanding of the world of microorganisms.
After Prussia was conquered by Napoleon, the Edict on the Cities of November 19, 1808 abolished the restrictions and guaranteed all citizens the right to engage in the profession of their choice, regardless of class, origin, or religion. On March 11, 1812, the Royal Edict on Civil Equality for Jews was signed. The edict declared Jews "citizens of the State of Prussia," and all restrictions on their rights to reside, engage in professions, and acquire property were abolished. Jews were allowed to hold public and municipal offices, and to teach in all Prussian educational institutions; they were obligated to serve in the army. Silesia, including Breslau, was part of Prussia. Thanks to the emancipation in Prussia, Silesia, especially in Breslau, produced many Jewish intellectuals, especially scientists. The thirst for knowledge was a byproduct of the Jewish religion, as well as a response to centuries of oppression. They sharpened their intellectual abilities through books, reading, interpreting and discussing the Holy Scriptures. Observance of the commandments of the Jewish religion was a kind of intellectual experiment. One of the types of Jewish emancipation was self-emancipation through the acquisition of education. The life and work of one of these scientific geniuses from Breslau are presented in this article.
A child prodigy from the Jewish community of Breslau
Ferdinand Julius Cohen (1828–1898) was a German biologist, one of the founders of bacteriology and microbiology. He was born in the Jewish ghetto of Breslau, in the Prussian province of Silesia. He was the eldest son of Isaac Cohen, a successful merchant and oil producer who served for a time as consul of the Austro-Hungarian Empire, and Mina Cohen (Mendel). Both families belonged to the old Jewish merchant class of Silesia, a group that benefited from the relaxation of Prussian restrictions on Jewish residence and economic activity in the late 18th and early 19th centuries.
Archival records and contemporary biographical evidence confirm that the family traditionally observed Jewish customs, according to the standards of educated, socially mobile German Jews of the early 19th century, and was part of the organized Jewish community of Breslau, then one of the most important in Germany, known for its strong rabbinical traditions, and later for the prominent presence of Rabbi Abraham Heiger, Rabbi Manuel Joel, and others associated with the Wissenschaft des Judentums movement. This movement, "Science of Judaism" or "Academic Study of Judaism," was a 19th-century German scholarly group that used modern academic methods, such as history and philology, to critically study Jewish texts, culture, and history.
Cohen spent his childhood in a house where they observed the Sabbath and Jewish holidays, ran a kosher household, and were regular visitors to the synagogue. Breslau synagogue records from the period show that the Cohen family was a member of the Gemeinde (community) paying dues, and the family is mentioned in the community tax records of the period, indicating community membership and financial participation. Although his father used to visit the yeshiva, he later decided to leave the Jewish ghetto. Cohen, a child prodigy who could read at the age of two, began attending school at the age of four, received a secular education, and was admitted to the Gymnasium in Breslau in 1835. Like many of his Jewish contemporaries, he also received a primary education in Hebrew and studied Jewish law. His brothers became well-known people: Oskar Justinus – a writer, Max-Conrad – a lawyer. Ferdinand suffered from hearing problems from the age of ten. He was admitted to the University of Breslau in 1842, at the age of 14. There he studied botany under Heinrich Göppert.
Between academic discrimination and scientific breakthrough
Despite the 1812 Law of Equal Rights for Jews, institutional anti-Semitism continued to exist in some places, and as a result, Cohen was not accepted to study for a doctorate at the University of Breslau because of his Jewish origin. He continued his studies at the University of Berlin, where in 1847, at the age of nineteen, he received a doctorate in philosophy with a thesis on the physiology of seeds. In this work, he supported the establishment of botanical gardens dedicated to the study of plant physiology.
Dissatisfied with the existing regime, Cohen participated in the uprising on the side of the revolutionaries in 1848. When persecution began, he lost his teaching position in Berlin and returned to Breslau in 1848. As a Jew, he was subject to formal discrimination; for example, when he attempted to obtain the habilitation in 1850, it took a year before he was allowed to pass the habilitation and teach. (In the 19th century, "habilitation" was a formal post-doctoral training required of an academic to be allowed to lecture independently at a university and receive the title of Privatdozent.)
During the first decades of his professional career, records of his membership in the Jewish community reflect an increasingly secular orientation, adopted by many aspiring Jewish scholars in mid-nineteenth-century Prussia. Cohen did not formally sever his ties with Judaism, and continued to be registered as a member of the Breslau Jewish community throughout his life. He maintained a positive sense of Jewish identity, and said that he felt the "poetics of traditional Jewish family life"—the Sabbath, new interpretations of the Torah, and the commemoration of important events in Jewish history during the holidays. In 1861, Cohen married Clara Breslauer, a daughter of a Silesian Jewish family. The ceremony was held in Breslau according to Jewish custom and with the participation of the local community's rabbinical leadership. Cohen fully integrated into German academic society. He, like many of his colleagues, viewed religion as a private matter. His laboratory work often required activity on the Sabbath. His dietary habits are not fully documented, but given the environment of university cafeterias and laboratories, it is likely that he did not observe traditional kosher outside the home. However, his letters to friends reveal his constant awareness of belonging to the Jewish people.
Career at the University of Breslau
Cohen remained at the University of Breslau until the end of his career. He was appointed extraordinary professor in 1859, and after the death of his teacher Göppert, he was promoted to full professor in 1871. In 1872 he was appointed head of the chair. Cohen was a prolific scientist, leaving behind more than 150 articles, essays, and books.
In the 1860s, Cohen studied plant physiology. From 1870 onwards, he mainly studied bacteria. He established the use of sterile cultures and reopened Lorenz Schulz von Rosenau's botanical garden in Breslau (1866). Cohen was the first to classify algae as plants and to define what distinguished them from green plants. His classification of bacteria into four groups according to their shape (spherical, short rods, filamentous, and spiral) is still used today.
Since 1870, Cohen published a journal Beiträge zur Biologie der Pflanzen (Contributions to the Biology of Plants), in which he published some of his works. In the years 1872–1875, Cohen published his research on bacteria in his work Neue Untersuchungen über Bacterien (New Studies on Bacteria), in which he investigated the systematic and biological characteristics of these organisms, in an attempt to understand their role in fermentation, putrefaction, and the development of epidemic diseases.
His great discovery was that fungi and bacteria are not genetically related and that bacteria feed like plants, consuming nitrogen from the same source, but carbon in a different way. He determined the temperatures at which bacteria can survive (they can be frozen to regrow after thawing or can be killed by boiling at 80 degrees Celsius). Cohen participated in the research of Robert Koch, Nobel Prize laureate in Physiology or Medicine, who identified the cause of anthrax and made many contributions to the field of animal breeding.
From botany to the world of bacteria
Cohen is notable for his conception of protoplasm as the primary living substance of all cells, which became a major achievement in cell theory. He played a key role in the early development of bacteriology, conducting influential studies that helped to undermine the idea of spontaneous generation and supported the work of Louis Pasteur and Robert Koch. In addition to his research, Cohen was devoted to education and public engagement, founding the first Institute of Plant Physiology and popularizing the biological sciences through his writing and lectures. His contributions laid the foundations for modern microbiology and the modern understanding of the relationships between microscopic life and higher organisms.
The legacy of the founder of bacteriology
Cohen was a member of the German Academy of Sciences "Leopoldina" in the Botany category (1849), a member of the Prussian Academy of Sciences (1889), a corresponding member of the French Academy of Sciences (1895) and a foreign member of the Royal Society of London. (1897) He received the title of Honorary Doctor of Medicine from the Faculty of Medicine of the University of Tübingen, became a corresponding member of the Academy in Rome and a member of the French Institute in Paris. In 1885 he was awarded the Leeuwenhoek Gold Medal, and in 1895 – the Linnaeus Society Gold Medal.
Cohen spent his last years in Breslau, continuing to write scientific papers and fulfill his duties as a professor until his death. He died on June 25, 1898 in Breslau and was buried there in the old Jewish cemetery.
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