Mutagenesis and Cloning of Photosynesis Genes of the Filamentous Bacterium, Chloroflexus aurantiacus

摘要

Chloroflexus aurantiacus is a green non-sulfur bacterium that preferentially grows photosynthetically under lighted, anaerobic conditions. The biosynthetic pathway for one of the photosynthetic pigments, bacteriochlorophyll c, is not well understood but may share common steps with the better understood bacteriochlorophyll a pathway. Cultures of C. aurantiacus were mutagenized in order to produce photosynthetic pigment mutants to be used later in the determination of intermediate compounds in the pathway for bacteriochlorophyll c synthesis. However, mutants with photosynthetic pigment deficiencies were not produced due to experimental difficulties. The photosynthesis genes of C. aurantiacus, such as the bchXYZ genes, are of evolutionary interest due to the similarities this bacterium has with the distantly related green sulfur and purple non-sulfur photosynthetic bacteria. The unknown bchXYZ sequences of C. aurantiacus could be used in comparisons with different families of bacteria to understand phylogenetic relationships between photosynthetic bacteria. Using degenerate PCR primers designed from known bchZ sequences, regions of the genome from C. aurantiacus were amplified, cloned, and sequenced. Sequence analysis indicated that the cloned regions corresponded neither to bchZ nor to other photosynthesis genes. Repetition of cloning experiments may yet reveal amplified regions corresponding to the bchZ gene.