Marjory Stephenson stands as one of the most influential figures in the history of biochemistry and microbiology, a scientist who essentially founded the field of chemical microbiology. Born on January 24, 1885, in Burwell, a village near Cambridge in Cambridgeshire, England, she overcame significant gender-based barriers in science to make groundbreaking contributions to bacterial metabolism. Her work laid foundational principles for understanding microbial physiology, enzyme regulation, and the unity of biochemical processes across organisms. In 1945, she became one of the first two women elected as Fellows of the Royal Society (alongside Kathleen Lonsdale), a landmark achievement that symbolized the slow opening of elite scientific institutions to women.
Early Life and Education
Stephenson was the youngest of four children by nearly nine years, born to Robert Stephenson, a prosperous farmer, surveyor, cement manufacturer, and local public figure (Justice of the Peace and Deputy Lieutenant of Cambridgeshire), and Sarah Rogers. Her family background in farming and horse breeding (both grandfathers were involved in Newmarket racing) provided a stable, intellectually curious environment. Educated initially by a governess who sparked her interest in science, she won a scholarship to Berkhamsted High School for Girls in Hertfordshire.
In 1903, at her mother’s insistence, she entered Newnham College, Cambridge, to study Natural Sciences (chemistry, physiology, and zoology). This was an era when women at Cambridge faced severe restrictions: they could not access many university laboratories, were barred from full degrees until 1948, and received only a “title to a degree.” Stephenson completed Part I of the Natural Sciences Tripos in 1906 with a second-class result. Despite aspiring to medicine, financial constraints led her into teaching domestic science at Gloucester County Training College and later King’s College of Household and Social Science in London.
Early Research and World War I Service
Her scientific career truly began when R.H.A. Plimmer invited her to his laboratory at University College London. There, she investigated fat metabolism, lactase from intestinal mucosa (demonstrating inhibition by glucose but not galactose), palmitic acid esters, and experimental diabetes. In 1913, she received a Beit Memorial Fellowship.
World War I interrupted this work. Stephenson joined the British Red Cross, managing hospital kitchens in France and serving as a Voluntary Aid Detachment (VAD) commandant in Salonika (Thessaloniki). Her service earned her an MBE and an Associate of the Royal Red Cross (ARRC); she was mentioned in despatches. These experiences fostered a lifelong pacifism, leading her later to join the Cambridge Scientists’ Anti-War Group.
Cambridge and the Birth of Chemical Microbiology
Post-war, Stephenson returned to Cambridge and joined Frederick Gowland Hopkins’ newly established Department of Biochemistry. Hopkins, a visionary mentor, encouraged her to shift from animal metabolism and vitamins to bacterial biochemistry—a move that defined her legacy. Supported initially by her Beit Fellowship and then the Medical Research Council (MRC), she thrived in an environment unusually supportive of women researchers (about 15% of the department).
Stephenson pioneered techniques like the “washed suspension” method (building on Pasteur) for studying bacterial enzymes in resting cells. With colleagues like Margaret Whetham and Juda Quastel, she advanced metabolic studies. A milestone came in 1928 when she and Leonard Stickland isolated the first bacterial enzyme from cells—lactic dehydrogenase from Escherichia coli.
Her work on anaerobic metabolism was particularly transformative. Inspired by river mud from the Great Ouse (observed fermenting due to sugar-beet factory waste), she explored hydrogen activation, naming the enzyme hydrogenase. With Stickland, she characterized formate hydrogenlyase (FHL), demonstrating its induction only in the presence of formate—an early, clear example of what she termed “adaptive enzymes” (now known as enzyme induction or regulated gene expression). This work prefigured insights by Jacques Monod and others in molecular biology.
Stephenson collaborated widely, including with Ernest Gale on amino acid metabolism and enzyme adaptation, and Arthur Trim on nucleic acids. Her approach emphasized studying the whole organism, integrating chemistry, biochemistry, and physiology, and recognizing bacteria as ideal models for cellular processes.
Bacterial Metabolism: A Lasting Legacy
Her most enduring contribution is the textbook Bacterial Metabolism, first published in 1930, with revised editions in 1939 and 1949 (reprinted as late as 1966). It synthesized knowledge of microbial biochemistry, serving as the standard reference for generations. The book highlighted regularities in bacterial metabolism analogous to higher organisms, supporting the “unity of biochemistry.” In later editions, she presciently discussed microbial genetics, nucleic acid metabolism, adaptive enzymes, and growth machinery—ideas written before the DNA double helix or the operon model.
Leadership, War Service, and Recognition
During World War II, Stephenson served on the Toxin Committee and contributed to wartime efforts, including biotechnological production and combating infections. She was a co-founder of the Society for General Microbiology (SGM, now Microbiology Society) in 1945, suggesting its name and serving as its second president in 1947 (after declining the first). In 1947, Cambridge appointed her its first Reader in Chemical Microbiology, a long-overdue permanent position.
Her Royal Society election in 1945, following advocacy by figures like J.B.S. Haldane, marked a breakthrough. She received a DSc from Cambridge in 1936 and was a dedicated mentor, inspiring students through practicals and research. Many of her trainees became leaders in their fields.
Personal Life and Character
Stephenson never married, devoting her life to science, gardening, and travel (including visits to the US and USSR in the 1930s). Described as dynamic, no-nonsense, and enthusiastic, she balanced rigorous research with generous mentorship. She faced undeclared discrimination but persisted through talent and determination. She died of cancer on December 12, 1948, at age 63, shortly after her university appointment.
Enduring Impact
The Microbiology Society established the Marjory Stephenson Prize Lecture in 1953 (its premier award) in her honor. Her emphasis on interdisciplinary approaches, whole-cell physiology, and environmental context remains relevant. Work on adaptive enzymes influenced molecular biology; studies of hydrogenase and anaerobic pathways underpin modern bioenergetics and biotechnology.
Stephenson’s career exemplifies pioneering a new field amid systemic barriers. As one obituary noted, she “made her way in science by pioneering her own field.” Her vision—that bacteria reveal fundamental life processes—continues to guide microbiology. In an era when women scientists were rare, Marjory Stephenson not only excelled but reshaped how we understand the microbial world.