LGT of the denitrification pathway. (A) Nitrite detection after 48 h of anaerobic incubation in the presence of nitrate 40 mM (column N), nitrite 5 mM (column Ni), or without electron acceptor (column C). Note that nitrate reduction results in the production of high nitrite concentrations (dark color), whereas nitrite consumption is detected as the lack of color. (B) SDS-PAGE of membrane proteins from the indicated strains stained with Coomassie blue. Strains: wild-type HB27 (lane wt); PRQ25 (lane PR); HB27 derivatives HB27nkat (lane nk), HB27dkat (lane dk), HB27d (lane d), and HB27C15 (lane C15).