Investigations into the Regulation of Short-Chain Fatty Acid Assimilation and Ethanolamine Metabolism in Bacteria

Abstract

Metabolism is the process of importing extracellular materials and degrading them for the purposes of biomass and energy. Acetyl coenzyme A (acetyl-CoA) is a keystone intermediate that is frequently the entry point into multiple cellular pathways. Two acetyl-CoA pathways, such as ethylmalonyl-CoA pathway (EMCP) and the glyoxylate bypass (GB), rarely coexist inside of the same organism. The genomes of two bacteria, Paracoccus denitrificans and Rhodobacter capsulatus, have the genes for both acetyl-CoA assimilation pathways. During growth with acetate, P. denitrificans utilizes both the EMCP and the GB. Additionally, R. capsulatus has the genes for two propionyl-CoA assimilation pathways. Propionyl-CoA can be assimilated through a branch of the EMCP called the methylmalonyl-CoA pathway or through the methylcitrate cycle. By using molecular cloning techniques to generate deletion and fusion strains, I investigated when the EMCP, the GB, the methylmalonyl-CoA pathway, and the methylcitrate cycle were active during growth with acetate or propionate. Our investigations with R. capsulatus indicate that R. capsulatus is possibly utilizing the EMCP and the GB differently than P. denitrificans. Investigating the EMCP, GB, methylmalonyl-CoA pathway, and methylcitrate cycle furthers our understanding of the biological control of these pathways. Because the EMCP shares reactions with bioplastics precursor molecules, understanding the mechanism of biological control of the EMCP and the pathways that intersect with the EMCP are critical for the possibility of proposing a mechanism of manipulation. This work investigates the operation and control of the EMCP, the GB, the methylmalonyl-CoA pathway, and the methylcitrate cycle in R. capsulatus.