The pigments of Staphylococcus aureus were isolated and purified, and their chemical structures were determined. All of the 17 compounds identified were triterpenoid carotenoids possessing a C3o chain instead of the C4o carotenoid structure found in most other organisms. The main pigment, staphyloxanthin, was shown to be aD -glucopyranosyl 1-0-(4,4'-diaponeurosporen-4-oate) 6-0-(12methyltetradecanoate), in which glucose is esterified with both a triterpenoid carotenoid carboxylic acid and a C15 fatty acid. It is accompanied by isomers containing other hexoses and homologs containing C17 fatty acids. The carotenes 4,4'-diapophytoene, 4,4'-diapophytofluene, 4-4'-diapo-±-carotene, 4,4'-diapo-7,8,11,12-tetrahydrolycopene, and 4,4'-diaponeurosporene and the xanthophylls 4,4'-diaponeurosporenal, 4,4'-diaponeurosporenoic acid, and glucosyl diaponeurosporenoate were also identified, together with some of their isomers or breakdown products. The symmetrical 4,4'-diapostructure was adopted for these triterpenoid carotenoids, but an alternative unsymmetrical 8'-apostructure could not be excluded.

Mutants of Staphylococcus aureus were isolated which showed changes in pigment composition compared with the parent strain. On the basis of differences in their triterpenoid carotenoid composition they were classified into seven types. In five of these types, there appeared to be a blockage in the biosynthetic pathway which resulted in the absence of some products and accumulation of others. The changes in the other two types appeared to be a consequence of some change in regulation. A scheme for the biosynthesis of triterpenoid carotenoids is presented in which the first C3M intermediate, 4,4'-diapophytoene, is converted via 4,4'diapophytofluene, 4,4'-diapo-D-carotene, 4,4'-diaponeurosporene, 4,4'-diaponeurosporenal, 4,4'-diaponeurosporenoic acid, and glucosyl-diaponeurosporenoate to the major pigment staphyloxanthin. We have previously described the isolation and identification of a series of carotenoids from

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