Skip to main content
. Author manuscript; available in PMC: 2015 Sep 1.
Published in final edited form as: Environ Microbiol. 2010 Oct 15;13(3):563–575. doi: 10.1111/j.1462-2920.2010.02357.x

Figure 1. A ppGpp deficiency abolishes regulation of RNA/DNA and RNA/protein ratios as a function of growth rate.

Figure 1

Isogenic strains differing in the presence of ppGpp were grown in different media (Table I) to achieve a range of balanced growth rates from about 120 min/doubling (μ = 0.5) to about 30 min/doubling (μ = 2). Cellular RNA and DNA content were measured by a fluorescent assay. Filled symbols correspond to wt strains, open symbols correspond to ppGpp0 strains. The solid lines represent linear regressions calculated with SigmaPlot software. (A) the wt (CF1648) and mutant (CF1693 = CF1648 ΔrelA251 ΔspoT207) strain are basically the same as used in earlier conflicting reports regarding the role of ppGpp in growth rate control (Gaal and Gourse, 1990; Hernandez and Bremer, 1993). (B) the wt (CF7968) and mutant (CF12257) strains used here are thought to be improved over the strains used in (A) with respect to the absence of polar effects due to insertions (ΔrelA256 ΔspoT212) and elimination of the leaky uracil requirement (see text for details) (C) Selected cell lysate samples from (B) were assayed to measure RNA/protein ratios.