Fig 1.
Effects of light and O2 on growth and N2 fixation in BAL398 under varying carbon (C) and nitrogen (N). (A) Growth rates (µ) and duplication times (Tg) under different light, O2, and N conditions. In red, the growth rate under aerobic conditions. (B) Cell abundance under different photon irradiance (from 0 to 250 µmol photons m−2 s−1) at N2 fixing (0.15 mM N) and anoxic conditions. (C) Growth under varying O2 levels (0, 100, and 250 O2 µM) at 35 mM C. (D) N2 fixation rates under different O2 concentrations and light conditions. (E) Cell abundance. (F) N2 fixation under different light, O2, C (0. 0.35, and/or 35 mM), and N availability (0, 0.15, and/or 7.5 mM). Note that in (F), N2 fixation was not measured at C = 0 mM and N = 0 mM. The values represent the mean, and the error bars indicate the standard error between the replicates (n = 3). Different letters indicate pairwise analysis among variables (P < 0.05), using a post hoc test (Wilcoxon) after Kruskal-Wallis over the whole data set. Plots (A−F) are from independent experiments. In (A), data points were recorded every day during 10 d, and in (B−F), values were measured after 7 d. For more detailed information about the conditions tested, please refer to Table 1, Section 1.