Characterization of the RpoN over-expression strain. Cell growth with fumarate as an electron acceptor was monitored by absorbance at 600 nm (a)(b). (a) acetate as the electron donor and fumarate as the electron acceptor (NBAF medium); (b): ammonia-free NBAF. Growth with Fe(III) as an electron acceptor was monitored by Fe(II) production (c) as well as cell numbers (d). Filled square: the WTV strain without IPTG; Empty square: the WTV strain with IPTG. Filled circle: the RpoN+ strain without IPTG; empty circle: the RpoN+ strain with IPTG. (a)-(d): Data are means ± standard deviations of triplicates. The production of pili was measured by agglutination assays (e). Data are means ± standard deviation of triplicates from two independent experiments (e).