TABLE 2.

Nitrite sensitivity test in 2.4.3 wild-type and ΔnorEF mutant strains^a

Initial [NO2−] (mM)	Nitrite sensitivity of strainb:
	2.4.3	2.4.3 ΔnorEF
0.5	++	++
1	++	−(+)
2	++	−−
5	+−	−−
10	−−	−−

^aCultures (n = 2 to 7) were treated with ∼1% initial O₂ and 0.5, 1, 2, 5, or 10 mM nitrite.

^b++, Balanced transition to denitrification, all of the available nitrite reduced to N₂O. −−, nitrite toxicity and arrest reflected either by the accumulation of μM concentrations of NO or a more general inhibition of oxic respiration and denitrification. +−, 1 out of 2 tested cultures reduced the available nitrite to N₂O. −(+), 3 out of 7 tested cultures reduced the available nitrite to N₂O.