Figure 2.

Growth of B. subtilis on OP depends on pxpA, pxpB, pxpC, and ycsG. A, growth at 37 °C of wild-type B. subtilis (closed circles) and various mutants with OP as the sole nitrogen source. There was no significant difference between growth of pxpA, pxpB, pxpC, or ycsG knock-out cells, which are all represented by open triangles; open squares represent the growth of ycsI knock-out cells. Data represent the mean ± S.E. of three independent cultures; the S.E. bars were smaller than the symbol for all cultures represented by open triangles. B, the indicated strains were grown overnight in LB medium, and washed twice with water, diluted to optical densities (600 nm) of 1.0, 0.2, 0.04, 0.008, and 0.0016, and 10 μl was spotted on medium with OP or ammonium as the sole nitrogen source. In the middle column, each strain harbored an expression plasmid carrying the respective gene that was deleted; the medium also contained 0.1% (w/v) xylose. Wild-type B. subtilis harbored the empty vector. Photographs were taken after 16 h (ammonium) or 72 h (OP) incubation at 37 °C and are representative of three independent experiments.