A synthetic medium for the L type colonies of Proteus.

The minimal requirements for growth of many Proteus strains were found by Fildes (1938) to be satisfied by a medium containing minerals, ammonium salts, lactate, and nicotinic acid. L type colonies, however, have only been grown on natural media, usually containing 10 to 20 per cent animal blood serum or other body fluids. Dienes and Weinberger (1951) state that Proteus 3B L type colonies will grow on nutrient agar without serum. The serum in complex natural media has been replaced by bovine albumin plus an acetone insoluble lipid fraction of egg yolk (Edward, 1953) and by riboflavin (Tulasne et al., 1950). Dienes (1953) states that Proteus L forms will not grow on a synthetic medium that supports growth of the rods. The present paper deals with amino acid media which support rapid growth of Proteus rods and L forms. L type colonies will be formed and will grow on a synthetic medium solidified with agar. The poor growth on natural media without added serum seems to be due to the presence of an inhibitor(s) found in several natural products, rather than the absence of growth factors.