The cyanobacterium <i>C. raciborskii</i> grown under diazotrophic conditions.

<p>(A) Light micrograph of <i>C. raciborskii</i> trichomes, magnified 40x. Note the terminal heterocysts at the end of the trichomes (white arrows); one heterocyst is magnified. (B) Percentage of trichomes with 10 to >100 vegetative cells are grouped according to their trichome length (no. of vegetative cells per trichome). The bars give the average numbers in 400 trichomes from 4 independent cultures. Standard deviation is given. The dashed line denotes the point where all trichomes have developed two end heterocysts. (C) The growth of <i>C. raciborskii</i> cultures, grown with 2 mM of NO₃⁻ to an OD₇₅₀ of 0.2, washed and transferred to new medium under the denoted light regime. Each point corresponds to the mean of 4 biological replicates. Standard deviation is given. (D) Western-blot analysis of NifH expression during a 12L/12D cycle (above). The NifH western-blot membrane was stripped and re-labelled with an antibody against the 30S ribosomal protein S1, revealing protein levels loaded in each well (below). The closest molecular marker band is indicated, and black and white bars represent the light and dark phase of the cycle. (E) Nitrogenase activity was analyzed by ARA for <i>C. raciborskii</i> under diazotrophic growth and continuous light (MLA₀ Cont light), diazotrophic growth and 12L/12D cycle (MLA₀ 12/12), and grown in MLA_N under 12L/12D cycle (MLA_N 12/12). Oxygen concentration was measured for MLA₀ 12/12 cultures and normalized to protein content. Each point corresponds to the mean of three biological replicates where standard deviation is shown.