There exist several extensions to OLS based methods such as generalized linear regression models (GLM) [12], Gompertz based models and others [13] that can be used to analyze and compare bacterial growth and similar types of studies. A recent approach used a non-parametric mixed effects-model based regression with random effects to handle the dependence between each consecutive point found in growth curve data [10]. The regression model was further improved by bootstrapping the regression coefficients so that a prediction band could be obtained for the modeled growth curve. We also demonstrate the use of GAM regression, which is an extension to spline regression, to model bacterial growth in one of the E. coli strains. GAMs are almost as easy to set up as standard linear regression models, but the use of splines makes GAMs better at modeling longitudinal data. Not only can a confidence interval be obtained for the whole curve, but we also show that derivatives, with confidence intervals, of the fitted curves can be easily computed, revealing more information with respect to how growth changes at each time point.