Pigment production by Lancefield-group-B streptococci (Streptococcus agalactiae)

Abstract

Cells of group-B streptococci harvested in the late exponential phase of growth and suspended in starch-glucose phosphate-buffered saline extractor solution were observed to form and release pigment into solution. Filtrates of these solutions were analysed spectrophotometrically and two varieties of pigment were detected. Pigment, when freshly produced or in the presence of starch, had four absorption peaks at 520, 485, 455 and 435 nm. If albumin was substituted for starch in the extractor solution or if the starch-pigment complex was disrupted by treatment with amylase or by boiling, the four-peak pigment rapidly and irreversibly degraded to a second type with a single absorption band at 415 nm. The pigments formed by washed cell suspensions had absorption spectra identical to those produced by pigment formed during growth in Todd-Hewitt Broth. The formation and release of soluble pigment appeared to be an active metabolic process; a carrier molecule and an energy source were both required. Pigment yields were increased when the pH of the extractor solution was in the range 7.0-7.4 and when Mg2+, but not other divalent cations, was present. No differences in yield or type of pigment were observed when pigment was formed in anaerobic conditions. These findings support an earlier observation that group-B streptococcal pigment resembles a beta carotenoid. There is some added support for the suggestion that haemolysin and pigment production by these organisms are closely linked characteristics.