Survival of recombinants relative to wild-type M. smegmatis. THP-1 macrophages were infected with an equal mixture of xylE-expressing bacteria and sur2 bacteria (hatched) or sur3 bacteria (horizontal stripe). The ratio of the recovered white-to-yellow colonies is shown for -2 hours (initial inoculum), 0 hours (immediately after phagocytosis interval), and at 3, 6, 9, 12, and 24 hours after phagocytosis. The ratios represent the average of the results of three independent experiments. Error bars represent the standard deviation in the ratio of white-to-yellow colonies between experiments.