The production of magnesium protoporphyrin monomethyl ester by Rhodopseudomonas spheroides

A monoester of magnesium protoporphyrin has been isolated by Granick (1961) from a chloro- phyll-less mutant of Chlorella and from etiolated barley leaves treated with 8-aminolaevulic acid and aaoc-bipyridyl.It was considered likely that this material was a methyl ester that Granick then proposed as an intermediate in the biosynthesis of chlorophyll.The extraction from Rhodop8eudomona spheroides of an enzyme system which methylates magnesium protoporphyrin to form the mono- methyl ester (Tait & Gibson, 1961) has been given as evidence for the participation of this metalloporphyrin in bacteriochlorophyll biosynthesis.In this paper is described the detection and identification of magnesium protoporphyrin monomethyl ester, which was secreted into the medium by intact cells of R. spheroide8, growing on complete medium and carrying out normal bacteriochloro- phyll synthesis. MATERIALS AND METHODS(Julture8.Rhodop8eudomonas spheroides, obtained from Dr J. Orlando, Brandeis University, was grown in the medium of Cohen-Bazire, Sistrom & Stanier (1957), supple- mented with 0-1% of Difco yeast extract, which was found in preliminary experiments to overcome erratic growth.Incu&bation conditions.Cultures were grown anaerobic- ally in the light in 500 ml.bottles with ground-glass stoppers.The bottles were placed in a glass-sided water bath at 310 and illuminated by 100w tungsten lamps so that light falling on the bottles was approximately 150 ft.- 419, 527, 553 and 591 m,u.