The fitness and macromolecular composition of the gram-negative bacterium E.coli are governed by a seemingly insurmountable level of complexity. However, simple phenomenological measures may be found that describe its systems-level response to a variety of inputs. This thesis explores phenomenological approaches providing accurate quantitative descriptions of complex systems in E.coli. Chapter 1 examines the relationship between unnecessary protein production and growth rate in E.coli. It was previously unknown whether the negative effects on growth rate due to multiple unnecessary protein fractions would add linearly or collectively to produce a nonlinear response. Within the regime of this thesis, it appears that the interplay between growth rate and protein is consistent with a non-interacting model. We do not need to account for complex interaction between system components. Appendix A describes a novel technique for real-time measurement of messenger RNA in single living E.coli cells. Using this technique, one may accurately describe the transcriptional response of gene networks in single cells. / Physics