Mary Jane Merten was born on September 24, 1927, in Colorado Springs, Colorado.^[3] Her family moved to Beverly Hills, California when she was five, and her father was very supportive of her scientific interests and ambitions.^[4]

She received a bachelor's degree in physiology from the University of California at Berkeley in 1948.^[5] She then earned a Ph.D. in biochemistry from the University of Washington in 1958, where her thesis research investigated the function of folic acid-dependent enzymes and vitamins.^[6] In 1957, while working in the laboratory of F. M. Huennekens,^[7] she discovered the mechanism of action of methotrexate, a pharmaceutical drug used to treat cancer, rheumatoid arthritis, and psoriatic arthritis.^[2]

After receiving her Ph.D., she began a postdoctoral microbiology fellowship at the New York University College of Medicine, and was appointed assistant professor there in 1962.^[5] In 1963, she joined the Albert Einstein College of Medicine as an assistant professor, and was promoted to associate professor in 1996.^[6]

She joined University of Connecticut School of Medicine as professor in 1968, where, as one of the founding members, she helped develop their medical school program.^[2] She served as professor of microbiology in the Department of Molecular, Microbial and Structural Biology^[5] and remained at the University of Connecticut until her retirement in 2014.^[2] While there, she served as a professor of microbiology and of molecular biology and biophysics, and headed the University of Connecticut's Department of Microbiology from 1980 to 2002.^[2]

It was during her postdoctoral fellowship that she switched research focus to microbiology, examining the biosynthesis of lipopolysaccharides^[8] which contributed to the development of new antibiotics.^[6] Lipopolysaccharides, also known as bacterial endotoxin, are large molecules that are abundant on the surfaces of Gram-negative bacteria and contribute to bacterial toxicity and the immune response they provoke.^[6]

She used a combination of biochemical experiments, bacterial genetics, and electron microscopy to investigate how bacteria transport lipopolysaccharides from the cellular interior where they are produced to the outer membrane where they reside.^[2] This work required the development of a new technique to separate the inner and outer membranes of Gram-negative bacteria, which became known as the Osborn method.^[2] She also researched the mechanisms of bacterial cell division.^[5]

Later in her career, she pursued an interest in space biology. Osborn worked for NASA and the National Research Council from the mid-1990s through 2008 on lunar and space exploration projects.^[9] In this capacity, she chaired NASA's Committee on Space Biology and Medicine, which helped plan U.S. space biology research in the early 2000s.^[2]

Osborn served as editor of the journal Biochemistry and the Journal of Biochemistry.^[3] She chaired the National Institutes of Health Advisory Council, Division of Research Grants from 1992 to 1994^[5] and served on the Council of the American Society for Biochemistry and Molecular Biology from 1974 to 1975).^[2] She was the second woman elected at their president (1981)^[2] and also served as president of the Federation of American Societies for Experimental Biology (1982).^[6]

She married painter Ralph Osborn. She had no children. She was interested in poetry and the arts, including ballet and opera.^[2]

Osborn died January 17, 2019, in Farmington, Connecticut, at the age of 91 following complications after emergency surgery.^[2]

Osborn was elected to the American Academy of Arts and Sciences in 1977, the National Academy of Sciences in 1978,^[2] and the American Academy of Microbiology in 1992.^[5] She was appointed to the National Science Board (governing body of the National Science Foundation) by President Jimmy Carter in 1980.^[2]

She was chosen for the Chancellor's Distinguished Lectureship at the University of California, Berkeley in 1982.^[5] In 2002, the University of Connecticut Medical School established an annual Osborn Lectureship to honor female scientists.^[2]

• Huennekens, F. M.; Kay, L. D.; Osborn, M. J.; Hatefi, Y. (August 1, 1957). "Hydroxymethyl Tetrahydrofolic Dehydrogenase". Journal of Biological Chemistry. 227 (2): 637–647. doi:10.1016/S0021-9258(18)70744-8. ISSN 0021-9258. PMID 13462986.
• Osborn, M. J.; Freeman, M.; Huennekens, F. M. (February 1958). "Inhibition of dihydrofolic reductase by aminopterin and amethopterin". Proceedings of the Society for Experimental Biology and Medicine. 97 (2): 429–431. doi:10.3181/00379727-97-23764. ISSN 0037-9727. PMID 13518295. S2CID 26551988.
• Parisi, E.; Gander, J. E.; Osborn, M. J. (June 25, 1972). "Mechanism of Assembly of the Outer Membrane of Salmonella typhimurium – Site of Synthesis of Lipopolysaccharide". Journal of Biological Chemistry. 247 (12): 3973–3986. doi:10.1016/S0021-9258(19)45128-4. ISSN 0021-9258. PMID 4624447.
• Carson, J.; Parisi, E.; Gander, J. E.; Osborn, M. J. (June 25, 1972). "Mechanism of Assembly of the Outer Membrane of Salmonella typhimurium – Isolation and Characterization of Cytoplasmic and Outer Membrane". Journal of Biological Chemistry. 247 (12): 3962–3972. doi:10.1016/S0021-9258(19)45127-2. ISSN 0021-9258. PMID 4555955.

• Interview with Mary Jane Osborn (2011), National Academy of Sciences