Bacteria (Pseudomonas fluorescens) was identified as heterotrophic
nilrifiers. The present investigation was carried out 10 study heterotrophic nitrification
activity in nutrient liquid medium With pH 6, 6.5 and 7. The growth at pH 6.5 was
higher than that of pH 6 and 7. During the exponential growth phase the intermediate
products of heterotrophic nitrification activity which excreted into the culture media
(nitrite, nitrate and hydroxlamine) were increased significanUy at pH 6.5lhan pH 6 and
7. At a constant C/N rauo 3: 1 glutamine was identified as a better nitrogen sourc for
heterotrophic nitrification than the other organic N-containing components: argi"ine
and asparagine.