Each dot represents measurements for a different isolate. The isolates and their corresponding competitors were sampled from the same stage of growth in order to measure the difference in chemotaxis. Cells were grown in a standard batch culture. Two (orange), eight (blue) and 11.5 hr (red) after inoculation, samples were taken and treated with the standard protocol before measurements. While incubation in capillary competition assay (30 min), swimming speeds were determined within 20 min after sampling. For the two-hour sampling, cells were concentrated by mild centrifugation; the other two points required proper dilution with washing buffer. For orange points, , ; blue points, , ; red points, , . Error bars indicate standard error from ~300 cells per data point.