FluxMPS™ Medium 199 (M199)

Medium 199 is a cell culture medium developed in 1950 by J.F. Morgan, primarily for cultivating chick embryo fibroblasts and other mammalian cells. It features a balanced composition of salts, amino acids, vitamins, and glucose, but lacks proteins and growth factors. Often used in virology and vaccine production, Medium 199 requires a CO2-enriched environment to maintain its pH. It supports various cell types and is typically supplemented with serum or serum-free additives for optimal growth. Its defined formulation makes it particularly valuable in large-scale vaccine manufacturing and biomedical research.

Origins & Development

Medium 199 (M199, also designated TCM 199 or Tissue Culture Medium 199) is the first completely defined, synthetic cell culture medium developed for the nutritional study of animal cells in vitro. Formulated in 1950 at the Connaught Medical Research Laboratories (CMRL) at the University of Toronto by Joseph F. Morgan, Helen J. Morton, and Raymond C. Parker, it represented an unprecedented attempt to replace all undefined biological supplements with a precisely characterized chemical mixture.

Unlike the Eagle-lineage media (BME, MEM, DMEM) that followed, built around the minimal nutrients needed to sustain proliferating cell lines, Medium 199 was engineered from a maximalist nutritional philosophy: every class of compound believed on theoretical grounds to be required by living cells was included, whether its individual necessity had been experimentally confirmed or not. This produced a uniquely complex formulation containing not only amino acids, water-soluble vitamins, and inorganic salts, but also fat-soluble vitamins (A, D2, E, K3), cholesterol, nucleic acid precursors (free purines, pyrimidines, nucleosides, nucleotides), and the surfactant polysorbate 80 (Tween 80) as a lipid dispersant, a nutritional scope not matched by any other classical medium.

Before 1950, all tissue culture media relied on undefined biological fluids, plasma clots, embryo extract, serum, and lymph as the principal nutritional components. These supplements were irreplaceable for cell maintenance, but their variable, unknown composition precluded controlled nutritional experiments. The CMRL group at the University of Toronto, under Raymond C. Parker, was at the forefront of replacing biological supplements with synthetic ones; the aim of the 1950 project was specifically to create a tool for the nutritional study of primary chick embryo fibroblasts under chemically defined conditions.

Morgan, Morton, and Parker published their foundational result in January 1950 as "Nutrition of animal cells in tissue culture; initial studies on a synthetic medium" in Proceedings of the Society for Experimental Biology and Medicine (73(1): 1-8). The paper described a fully synthetic feeding solution combining amino acids, vitamins, nucleic acid constituents, and accessory growth factors. The authors demonstrated that explanted chick embryo cells could survive in this mixture without serum for an average of four to five weeks, with measurable growth — results not achieved with any prior synthetic formulation. The investigators noted that while Medium 199 sustained cell life and permitted nutritional study, it was insufficient for long-term proliferation without serum, a limitation acknowledged in the original paper and all subsequent product documentation.

The number "199" reflects the sequential numbering of experimental formulations tested during development, not a count of components. Yao and Asayama (2017) describe the philosophy precisely: Medium 199 includes fat-soluble vitamins, cholesterol, and other components considered necessary on theoretical grounds, some of which proved physiologically inactive. This placed Medium 199 in deliberate contrast with the subsequent Eagle approach (1955-1959), which sought to define minimal requirements empirically; Eagle criticized Medium 199's complexity, noting that it included many components demonstrably unnecessary for HeLa and L-cell growth, and used this as the rationale for developing BME.

Tween 80 and the Delivery of Fat-Soluble Vitamins

The introduction of Tween 80 into the Medium 199 program is documented in Morton, Morgan & Parker (1950), "Nutrition of animal cells in tissue culture. II. Use of Tweens in synthetic feeding mixtures" (Proc. Soc. Exp. Biol. Med. 74: 22-26). Delivering fat-soluble vitamins was a practical problem, since vitamins A, D2, E, and K3 (menadione) are insoluble in aqueous media. Polysorbate 80 served as a nonionic surfactant vehicle that maintained these lipophilic compounds in stable suspension. Tween 80 also emulsifies cholesterol (0.2 mg/L), the only sterol present in any classical cell culture medium; this Tween 80 plus cholesterol pairing is absent from all subsequent Eagle-lineage media (BME, MEM, DMEM, IMDM, RPMI 1640).

Connaught Lineage: Medium 199 and CMRL 1066

Medium 199 and CMRL 1066 (Parker et al., 1957) both emerged from the same CMRL group and share a direct developmental relationship. CMRL 1066 was created by amending Medium 199 to culture mouse L cells under protein-free conditions: increasing the reducing substances cysteine, glutathione, and ascorbic acid; eliminating the fat-soluble vitamins (A, D, E, K3) and Tween 80; changing the nucleic acid precursors; and adding five preformed coenzymes (CoA, TPP, NAD, NADP, FAD). CMRL 1066 is thus a more metabolically sophisticated, serum-free-optimized descendant of Medium 199's complex basal framework.

Medium 199 and the 1955 Salk Polio Vaccine

The most historically consequential application of Medium 199 was as the growth medium for the poliovirus used to produce the first Salk inactivated polio vaccine. Following the Enders-Weller-Robbins discovery that poliovirus could be grown in non-nervous tissue cultures (Nobel Prize, 1954), Medium 199 was selected as the nutrient medium for growing poliovirus in monkey kidney cell monolayers. Contemporary accounts describe minced monkey kidney tissue placed in "Povitzky bottles" filled with Mixture 199, incubated at 36-37 degrees C for several days to form a kidney-cell monolayer, after which fresh Mixture 199 was added and poliovirus seed inoculated; the virus multiplied for several days before harvest. The April 12, 1955 announcement of vaccine efficacy and the subsequent mass inoculation of millions of children marked the first global public-health triumph in which a chemically defined synthetic medium played a central role in manufacturing.

Cholesterol / Tween 80 compatibility. Polysorbate 80 can interact with lipophilic membrane components and certain cell types above the recommended range, and with some plastics, protein-binding surfaces, and filtration membranes; verify the concentration (4.9-20 mg/L) when changing suppliers.

Glutamine instability. L-glutamine (100 mg/L) is subject to spontaneous cyclization to pyroglutamate; store at 2-8°C and use within shelf life, or use a stable dipeptide (L-alanyl-L-glutamine).

Fat-soluble vitamin photodegradation. Vitamins A, D2, E, and K3 are photosensitive; store in a light-protected manner at 2-8°C and use freshly prepared medium promptly.

Serum dependency. Despite its complexity, Medium 199 does not support continuous proliferation without serum for most cell types — it is a complex basal medium, not a serum-free system.

Nucleotide precursor redundancy. Many nucleic acid precursors are physiologically redundant in proliferating lines with intact biosynthetic pathways; their benefit is greatest in cells with impaired de novo synthesis (primary explants, low density, metabolic stress).