Bi1X_Week6_GrowthCurves_v2_2011

Bi1X_Week6_GrowthCurves_v2_2011 - Bi 1X, Spring 2011 Week 6...

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Bi 1X, Spring 2011 Week 6 Session 1: Growth Curves Background: Cell Growth and Spectroscopy While there are a multitude of important time scales in biology, arguably one of the most important is concerned with the rate of cell division. In the bacteria E. coli , rates of cell division are closely linked with evolutionary fitness and hence our basic understanding of natural selection. To better understand the concepts involved in cell division, we will measure the bulk growth rate of E. coli in media with different amounts of antibiotic. We measure cell growth using spectroscopy and optical density as outlined in the following section. The included formulas will prove useful in analyzing your spectroscopic data. Beer’s Law and Optical Density It is often extremely useful to know the concentration of cells in a liquid culture, and can be used in various kinetic measurements of fitness and protein production. Light scattering is the primary method by which we measure cell density. In the following section, we will discuss the basic physical concepts that allow determination of concentration as well as the formulas that relate optical properties to concentration. The basic physics are as follows: 1. Light, with a wavelength comparable to the size of the object being measured (600 nm), enters the sample at an initial intensity (
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Bi1X_Week6_GrowthCurves_v2_2011 - Bi 1X, Spring 2011 Week 6...

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