Spectroscopic properties and bacteriochlorophyll c isomer composition of extramembranous light-harvesting complexes in the green sulfur photosynthetic bacterium Chlorobium tepidum and its CT0388-deleted mutant under vitamin B12-limited conditions

The effects of exogenous vitamin B 12 on the green sulfur photosynthetic bacterium Chlorobium ( Chl. ) tepidum were examined. Wild-type cells and mutant cells lacking a gene CT0388 (denoted as VB0388) of Chl. tepidum were grown in liquid cultures containing different concentrations of vitamin B 12 . The VB0388 cells hardly grew in vitamin B 12 -limited media, indicating that the product of CT0388 actually played an important role in vitamin B 12 biosynthesis in Chl. tepidum. Both wild-type and VB0388 cells in vitamin B 12 -limited media exhibited absorption bands and CD signals at the Q y region that were shifted to a shorter wavelength than those of cells grown in normal media. BChl c isomers that had S -stereochemistry at the 3 1 -position tended to increase in Chl. tepidum grown in vitamin B 12 -limited media.