FIG. 2.

Growth test on nitrite-containing media showing the effects of interruption and deletion of the cyn genes in the NA3 strain and expression of the cyn genes in the NA3 derivative defective in the cynABD genes (NA4). Synechococcus cells (n = 10⁶) were spotted onto solid medium containing 7.5 mM ammonium, 5 mM nitrite, or 0.5 mM nitrite and buffered at the indicated pH value and incubated under illumination for 4 days. Where indicated, isopropyl-β-d-thiogalactopyranoside (IPTG; 0.1 mM) was added to induce the expression of the plasmid-borne genes. WT, wild type.