Some Mutational Changes in the Photosynthetic Pigment System of Rhodopseudomonas spheroides

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Abstract
SUMMARY: Some 50 mutants, which differ from the wild type in the nature of their pigment systems, were isolated from the non-sulphur purple bacterium, Rhodo-pseudomonas spheroides. They fall into five main groups. The group of colourless mutants is incapable of photosynthetic growth, and devoid both of chlorophyll and carotenoids. The remaining groups still contain bacteriochlorophyll, but differ chemically from the wild type and from one another in their carotenoid pigments; all are capable of photosynthetic growth. The wild type contains two principal carotenoids, one red and one yellow. The dark red mutants contain both wild-type carotenoids and traces of a new red carotenoid. The brown mutants contain approximately equal amounts of the wild-type yellow carotenoid and of neurosporene, together with traces of the wild-type red carotenoid. The green mutants contain neurosporene and a dihydroxy derivative, but neither of the wild-type pigments. The blue-green mutants contain phytoene, a colourless polyene, but are completely devoid of coloured carotenoids. The infra-red spectrum of cells of the blue-green mutant is markedly different from that of the wild type and of the other photosynthetic mutants, despite the fact that its chlorophyll is chemically identical with theirs.