Friday, October 28, 2011
Hall 1-2 (San Jose Convention Center)
The green sulfur bacterium Chlorobaculum tepidum is a photosynthetic organism that utilizes a light-harvesting complex called the chlorosome. The chlorosome is an aggregate of hundreds of thousands of light absorbing pigments encapsulated by a lipid monolayer envelope. While in vitro experiments have shown that these pigments are capable of self-assembling into well ordered aggregates, the in vivo process of assembly, or biogenesis, of these complexes remains poorly understood. One aspect of chlorosome biogenesis that remains a mystery is how the size of chlorosomes is controlled. Previous work has shown that C. tepidum alters the size of its chlorosomes in response to variations in growth conditions, such as temperature, light intensity, and media composition. What remains unclear is whether this change in size is the result of the modification of existing chlorosomes or whether size is controlled only during the initial formation of the chlorosome. Atomic force microscopy is a method that allows the measurement of chlorosome size in all three dimensions under conditions very close to their native state. This technique will be utilized to characterize the size distribution of chlorosomes on membrane fragments isolated from cells grown under various conditions and at various time points following a change in growth conditions. This information should allow the determination of whether chlorosome size is controlled dynamically in response to the cell’s current environment or if it is only controlled at the time the chlorosome is formed.