Anhydrides of the Pentitols and Hexitols

1. Certain water-soluble esters of long chain fatty acids (in particular of oleic acid) favor submerged and diffuse growth of mycobacteria throughout the depth of synthetic liquid media. 2. Esters of oleic acid increase considerably the amount of growth yielded by avian strains in synthetic media. 3. The addition of serum albumin to synthetic liquid media permits visible growth of minimal inocula of virulent human tubercle bacilli (10–8 mg.) within 11 to 15 days. 4. Cultures growing diffusely in media containing the water-soluble esters— with or without albumin—consist of cells of classical morphology and staining properties, which again exhibit the usual mode of growth when returned to the standard synthetic or egg yolk media. Show more

Serum albumin is a protective bacterial growth factor; by binding traces of fatty acid in the media it permits initiation of growth by the smallest possible inocula of tubercle bacilli. Each molecule of albumin binds 3 to 6 molecules of oleic acid (1 to 2 per cent of the weight of the albumin) tightly enough to prevent bacteriostasis, and 9 molecules of oleic acid in equilibrium with a saturated neutral solution. The property requires undenatured albumin. Crystalline β-lactoglobulin has a smaller capacity, and a number of other proteins no perceptible capacity to bind oleic acid. The inhibitory effect of the commercial product Tween 80 (polyoxyethylene sorbitan monooleate) on the growth of small inocula of tubercle bacilli in liquid media is caused by its content of unesterified oleic acid (0.6 per cent by weight). Purified Tween 80, freed of this contaminating fatty acid, not only permits growth of small inocula, but protects against small amounts of added oleic acid. The implications of the binding capacity of albumin for its possible physiological significance in the animal body (transport; protection against cytotoxins), and for the structure of the protein, are briefly discussed. Show more