E.coli growth curves. The figure shows the bacterial growth curves for 13 different E. coli strains exposed to different amounts of lactoferrin growing in LB and Syncase broth. The horizontal axes represent time in minutes, while the vertical axes show optical density illustrating bacterial growth as measured using OD at 620 nm. For both LB and Syncase broth three different concentrations of lactoferrin were added: 0, 3, 8 mg/ml (designated POSLB, 3LB and 8LB, respectively) for LB and 0, 0.5, 3 mg/ml (designated POSS, 05 S, and 3 S, respectively) for Syncase. The blue line represents the empirical growth curve of the triplicates, while the red line represents the linear spline regression modeled growth curve. The dashed vertical lines represent the knots dividing the spline modeled growth curve into three intervals. The estimated slopes of each line segment resulting from the spline regression were used to compare the growth rates of the different strains.