Fig. 1
From: Biological methane production under putative Enceladus-like conditions
Influence of the different headspace gas compositions on growth of M. marburgensis, M. villosus, and M. okinawensis. The error bars show standard deviations calculated from triplicates. OD curves of a, d, g, j, m M. marburgensis, b, e, h, k, n M. villosus and c, f, i, l, o M. marburgensis for a–c H2/CO2, d–f H2/CO, g–i H2, j–l Mix 1, and m–o Mix 2. Growth of M. marburgensis was inhibited by the presence of C2H4 (see Table 2 for detailed gas composition). Only M. marburgensis seemed to be able to use sodium hydrogen carbonate (supplied in the medium) as C-source in case of a lack of CO2 (H2 or H2/CO as sole gas in the headspace). Both, M. villosus and M. okinawensis showed growth when Mix 1 and Mix 2 were applied to the serum bottle headspace; however, M. villosus exhibited extended lag phases. The dips in the graphs b, c were caused by substrate limitation due to depletion of serum bottle headspace of H2/CO2 at high-optical cell densities
