CRUDE OIL TOXICITY TOLERANCE OF HYDROCARBONOCLASTIC STRAIN OF CITROBACTER AMALONATICUS -Y2ESW1 ISOLATED FROM ESTUARINE SEDIMENT IN THE NIGER DELTA OF NIGERIA

Crude oil toxicity possess a major threat to the aquatic ecosystem in the Niger Delta. This study investigated the   inherent tolerability potential of hydrocarbon degrading strain of Citrobacter amalonaticus  - Y2ESWS1  to crude  oil toxicity.  Sediment samples were obtained from selected locations and subjected to   bacteriological analysis using standard methods. Bacterial identification result revealed taxonomic group of hydrocarbon utilizing bacteria species including Citrobacter amalonaticus strain Y2ESWS1. Toxicity testing revealed that the toxicant concentration and exposure time were key variables that mediated toxicity. A second-order polynomial regression model revealed significant (P<0.05, 0.01; R2=0.9852) relationship between exposure time and bacterial growth at 20% crude oil. Citrobacter amalonaticus strain - Y2ESWS1 was tolerant to crude oil toxicant concentrations as was evidenced in its prolonged acclimation periods. In this study the toxicity of pollutants to bacteria cultures (Citrobacter amalonaticus strain Y2ESW1,) was highly dependent on the concentration of the toxicants. The bacterial proliferation was hindered by 20% toxicant. It is a pointer to its poor activity when exposed to hydrocarbon however it can be used in a consortium with other microbes including potent degraders to achieve enhanced degradation of contaminated site.