ISOLATION OF DIAZOTROPHIC BACTERIA IN CRUDE OIL- INUNDATED SOIL

Contamination of the ecosystem by crude oil affects the microbial diversity and activities in the affected environment. This study examined the effect of crude oil pollution on the population of diazotrophic bacteria from crude oil inundated soil. A total of 8 samples were collected from 4 different point of crude oil impacted soil (NBPT1, NBPT2, NBPT3 and NBPT3) in Nembe (from the depth of 0-15cm and 15-30cm) and unpolluted sample (control) and the samples were transported aseptically to the laboratory for analysis. APHA methods were used for physicochemical analysis while culturing was on selective; Winogradsky 1, Winogradsky 2, Rhizobium and Azobacter media incubated at 28oC ± 2oC. Average total petroleum hydrocarbon concentration of 17600mg/kg was recorded which is higher than the 5000mg/kg intervention limit. The count of Nitrifying bacteria (Nitrobacter ) obtained ranged from 1.22×106CFU/g to 4.8 ×108CFU/g with the control sample having the highest count while the sample, NBPT1 (15-30cm) recorded the lowest count. The count of nitrosomonasranged from 1.21×106 to 1.64×108 with the control sample recording the highest count and the lowest count was recorded in the sample NBPT3 (15-30cm). The count of Azobacter ranged from 1.17×106CFU/g to 4.3×108CFU/g with the control sample having the highest count and the lowest count was in the sample, NBPT3 (15-30cm). The count of Rhizobium ranged from 1.78×106CFU/g to 2.9×108CFU/g with the control sample having the highest count and the lowest count of Rhizobium was recorded in the sample NBPT1(15-30cm). The study showed that crude oil spill and soil depth resulted in the reduction in population of the different diazotrophic bacteria groups.