In this thesis, the importance of rare codons on protein biogenesis as well as cell fitness will be discussed. To test the effects of rare codons, a continuous cell culture device known as a turbidostat was built and optimized within the lab. The turbidostat, as well as batch culture, is used to test the extent to which rare codons affect an antibiotic resistance protein known as chloramphenicol acetyltransferase (CAT). CAT has three known types (I, II, and III), and is responsible for the acetylation of the antibiotic chloramphenicol. There are two main methods that are used to test the fitness effects of different CAT-III constructs, one of which is a competition between two strains, and the other is a CAT assay to directly measure chloramphenicol conversion rates.