Catalyzes nitrate uptake, nitrite uptake and nitrite export across the cytoplasmic membrane. May function as a nitrate/H(+) and nitrite/H(+) channel. Could confer a selective advantage during severe nutrient starvation or slow growth. Expressed preferentially during the stationary phase in the absence of nitrate. Belongs to the major facilitator superfamily. Nitrate/nitrite porter (TC 2.A.1.8) family.