Bacteriochlorophyll Synthesis and the Ultrastructure of Wild Type and Mutant Strains of Rhodopseudomonas spheroides

The ultrastructure of sectioned cells of mutant and wild type Rhodopseudomonas spheroides has been examined by electron microscopy. The characteristic vesicles associated with the presence of bacteriochlorophyll were found in wild type cells grown with low aeration. These were also found in mutant TA-R which forms bacteriochlorophyll under high aeration. None of the mutants with blocks in bacteriochlorophyll synthesis contained intracytoplasmic membrane. These included mutant 8-17 which accumulates bacteriochlorophyllide but fails at the phytolation step. We conclude that the intact bacteriochlorophyll molecule, or some particular membrane protein associated with it, is needed for the development of the characteristic intracytoplasmic membrane system in R. spheroides.