Chromogenesis by variants of Staphylococcus aureus.

Chromogenesis in Staphylococcus aureus has received considerable attention, although today it is generally accepted that pigmentation in this organism is of little taxonomic value. Numerous carotenoid pigments from this organism have been characterized (B. Sobin and G. L. Stahly, J. Bacteriol. 44:265, 1942). The purpose of this investigation was to determine whether the variations in pigmentation of a parent strain of S. aureus and chromogenic variants were due to either quantitative or qualitative differences in in their production of carotenoids. The parent strain, S. aureus 6, and four spontaneous chromogenic variants (Table 1), all phage-typing 80/81, were isolated and grown on milk-agar as reported by J. Parisi (J. Bacteriol. 92:589, 1966), Growth from milk-agar was suspended in physiological saline, washed three times by sedimentation in a centrifuge from saline suspensions, and the suspensions were adjusted to the same optical density with a Bausch & Lomb Spectronic-20 colorimeter. The standardized suspensions were then sedimented by centrifugation, and the supernatant fluids were discarded. The extraction and partition of carotenoid pigments into hydrocarbons, alcohols, esters, and acids were according to the method of B. Sobin and G. L. Stahly (J. Bacteriol. 44:265, 1942), as modified by M. P. Starr and W. L. Stephens (J. Bacteriol. 87:293, 1964). Purification was by column chromatography with alumina used as the adsorbent for carotenoid hydrocarbons and calcium carbonate for carotenoid alcohols and esters. Petroleum ether (PE) was the solvent, PE containing 2% acetone was the developer, and PE containing 10% acetone was the eluent for the pigments during column chromatography. The absorption spectra of the purified pigments were determined in carbon disulfide with a Bausch & Lomb Spectronic-505 recording spectrophotometer.