Bacteria Hunters

Antibiotics Awareness week celebrated in November reminds us that it’s hard to imagine a world before antibiotics. The early 20th century discovery of the “magic bullet” rocked the medical world and turned once deadly infections into a quick trip to the doctor’s office. The problem now is that diseases once effectively treated with antibiotics are mutating and returning even stronger. It turns out the magic bullet can be over-prescribed and overused, and overuse causes resistance and stronger bacteria. At a time when dangerous super-bacteria are drawing increasing attention of the world’s microbiologists, we turn our special collections spotlight to some key foundational work for the field of bacteriology done by a 19th century German scientist. 

Ferdinand Cohn was a botanist who earned himself lasting fame with the  essays on bacteria that he first began publishing the early 1870s in Beiträge zur Biologie der Pflanzen, a journal he had just launched as professor and director of the Institute of Plant Physiology at the University of Breslau (now known as the University of Wrocław in Wroclaw, Poland.)  Cohn's most widely acclaimed essay "Über Bacterien, die kleinsten der lebenden Wesen"  was also published in 1876 as part of a German series of popular science lectures, where it caught the eye of American medical student Charles S. Dolley at the University of Pennsylvania, who hoped to help make the "best writings in medicine and science" from the German and French medical literature more widely available to aspiring young American scientists-in-training. Dolley's translation, "Bacteria: The Smallest of Living Organisms,"  first appeared as a limited edition pamphlet published in Rochester, N.Y. in 1881, and was later picked up by the Johns Hopkins University Press in the Bulletin of the History of Medicine (January 1939).

Don't let the size — 31 pages — of this slim publication fool you, for it summarizes profoundly important insights that the botanist had achieved in his study of algal, bacterial, and fungal microorganisms. With his work, Cohn established a robust definition of bacteria as chlorophyll-free cells that could be classified into four basic morphological forms — cocci, bacilli, vibrios and spirilli (see the illustration at the beginning of this blog for the visuals he provided along with that classification). He gave decisive intellectual weight to an understanding of bacteria as form-constant species in their own right, rather than organisms that evolve into something else. And Cohn recognized for the first time that some bacteria can undergo a spore stage—a stage in which otherwise actively reproducing bacteria cells assume a dormant form that allows them to survive exposure to unfavorable physical (e.g. high heat) or chemical (e.g. antiseptic agents) environments .

It's hard to overstate the importance of Cohn's analysis for the major breakthroughs in bacteriology that ensued. By the mid-1870’s Cohn’s ingenious work had attracted the attention of a young country physician, Robert Koch, whose research on anthrax was quietly laying the groundwork for modern medicine's understanding of bacteria as causative agents of infection. Cohn became a key supporter of Koch’s research, publishing Koch's seminal paper about bacillus anthracis in his Beiträge journal series in 1876, and also collaborating with him in some further studies. The rest is glorious science history, as the insights achieved by both scientists proved fundamental to all the later work establishing effective ways to treat bacterial infections, including of course Alexander Fleming’s discovery of penicillin in the late 1920’s. 

As microbiologists of today turn their attention to the problem of increasingly antibiotic-resistant super-bugs, it’s easy to imagine their intellectual forbears, the Cohns, Kochs, Flemings and the other greats of modern bacteriology, cheering them on — with no small sense of urgency — in their important work on behalf of global health. We might also do well to imagine these giants of science history reminding us that the global public has its own role to play in understanding how bacteria work and what steps we can take in our own habits and industry practices to hold the line against growing antibiotic resistance. For further thoughts on that, be sure to check out the info pages by the Center for Disease Control and the World Health Organization. 

Additional references: 

Drews, Gerhart, "The roots of microbiology and the influence of Ferdinand Cohn on microbiology of the 19th century," FEMS Microbiology Reviews, Volume 24, Issue 3, 1 July 2000, Pages 225–249, https://doi.org/10.1111/j.1574-6976.2000.tb00540.x

“Ferdinand Cohn, German Botanist,” Encyclopaedia Britannica https://www.britannica.com/biography/Ferdinand-Cohn

Gradman, Christoph, "Cohn, Ferdinand Julius," https://onlinelibrary-wiley-com.proxy.library.cornell.edu/doi/10.1038/npg.els.0002386

Leikind, Morris C., Introduction to "Bacteria: The Smallest of Living Organisms," translated by Charles S. Dolley, Bulletin of the History of Medicine, January 1939, via jstor.org (https://www.jstor.org/stable/pdf/44440427.pdf?refreqid=excelsior%3A4129cd9688644f0c8cbfcf67fb8c40a9) 

Seidensticker, Oswald, Introduction to Ferdinand Cohn's  "Über Bacterien, die kleinsten der lebenden Wesen" German Scientific Monographs for American Students, Boston: Henry Holt & Co.,  1889, via hathitrust.org (https://babel.hathitrust.org/cgi/pt?id=hvd.hxdcmt;view=1up;seq=7)