FIG 5.

Qualitative (A) and quantitative (B) analysis of Nar2-dependent nitrite production by developmentally arrested (nongerminated) spores of S. coelicolor. (A) Nar-dependent nitrate reduction was determined for the S. coelicolor strains, as indicated in Materials and Methods. Spore suspensions (5 μl of a suspension with an OD₄₅₀ of 20) were dropped on the plates, which were immediately incubated under anaerobic conditions for 3 days at 30°C. The plate on the right was prepared and processed in the same manner as the plate on the left but without chloramphenicol. Where indicated, 200 μg ml⁻¹ chloramphenicol and 5 mM sodium nitrate (NO₃⁻) were included in the medium. The presence of nitrite is revealed as a dark violet staining of the well. (B) Nar2-dependent nitrate reduction by NM59 (Δnar-1 Δnar-3) was determined quantitatively in anaerobic spore suspensions (suspensions with OD₄₅₀s equivalent to 5) at 25°C (filled circles) and at 30°C (filled triangles). Spore suspensions were incubated in MOPS-NaOH with 5 mM nitrate for 6 days under a nitrogen atmosphere. A control spore suspension containing 200 μg ml⁻¹ chloramphenicol (open circles) was incubated anaerobically, and a further spore suspension was incubated aerobically (open triangles, which are hidden by the open circles).