Isolation and Identification of Nitrifying Bacteria from Rhizosphere Soil of Phaseolus vulgaris (Bean Plant)

ABSTRACT
A study on the isolation and identification of nitrifying bacteria from the rhizosphere soils of Phaseolus vulgaris (bean plant) was carried out. The isolation and differentiation of the nitrifying bacteria into their various groups were carried out by first using the general purpose media, nutrient agar, and then inoculating pure cultures of the isolated colonies into the inorganic selective media; ammonium salt and nitrite broths to isolate and differentiate the nitrifying bacteria into their various groups respectively. The ammonium salt and nitrite broths were incubated at 37oC for 15days and 7days respectively, and observed for growth at intervals. Also, Griess Illosvay reagent was used to confirm the presence of nitrifiers in the ammonium salt and nitrite broths. The biochemical tests that the isolates were passed through reveal that Nitrosococcus nitrosus, Nitrosomonas europaea, Nitrobacter winogradskyi, Pseudomonas stutzeri, and Beggiatoa spp. are present in the rhizosphere soils of bean plants. In general, Nitrosococcus nitrosus had the highest frequency of occurrence, constituting half of all the isolates (50%) while Nitrosomonas europaea had the least frequency of occurrence with 6.25%.