(746b) Design Principles of Bacterial Organelles

Carbon fixation is the defining biosynthetic reaction of an autotrophic organism. It also presents numerous catalytic challenges to the host, which must possess specific mechanisms for concentrating carbon and catalyzing fixation in the proper place and time. One such example is the carboxysome, a microcompartment structure that encapsulates the key enzyme of the Calvin Cycle, RuBisCO, and facilitates carbon fixation in cyanobacteria and chemoautotrophs. Although there is considerable genetic and structural data regarding the carboxysome, there are still numerous unanswered questions about how this complex assembles in vivo and actually facilitates carbon fixation. We present here a comparative cell biological and biochemical analysis of carboxysome function in two organisms, S. elongatus and H. neapolitanus. Using these systems, we are investigating the biophysical properties of the carboxysome, including the nature and specificity of self-assembly and what endows its organelle-like function. In addition, we have recently demonstrated that carboxysomes may be transgenically expressed in heterologous hosts. To this end, we will discuss future bioengineering opportunities for using this structure to facilitate carbon fixation in novel organisms, and ultimately, how microcompartments can be used in the construction of synthetic organelles.