Screening And Characterization Of Alkane Degrading Bacteria In Polluted Soil From Dagang Oilfield

In this study,4 strains that can take crude oil as the sole carbon source were isolated and screened from the soil contaminated by crude oil for a long time in Dagang Oilfield,and 2 strains with high crude oil degradation rate were named BD and FR.By observing the morphological characteristics,it was found that BD was a round,about 1.5mm in diameter,with neat edges and slightly elevated white smooth bacterial colonies.The FR colony is off-white with neat edges with spines,round and opaque.Microscopic observation shows that the bacteria are rods containing elliptic spore.After the 16 S r RNA identification of BD and FR strains,the sequences of the two strains were compared by BLAST,and phylogenetic tree construction by MEGA X was analyzed.It was found that the similarity between BD and Acinetobacter SP.Strain White Regular was up to 100%,and they were in the same branch of the evolutionary tree.The similarity between FR and Bacillus Flexus strain MP-9 is as high as 99.79%,which is in the same branch of the evolutionary tree,indicating that FR has the closest relationship with Bacillus Flexus strain.Combined with the morphological characteristics of the bacterial colony and bacteria,the biochemical identification results determined that the strain BD was Acinetobacter Johnsonii and the strain FR was Bacillus Flexus.There are many reports on Pseudomonas and Bacillus in current studies,but relatively few reports on acinetobacter.The discovery of this strain is of positive significance for enriching the species resources of crude oil degrading bacteria.Through the strain growth curve,salinity,PH value,temperature,substrate concentration and other environmental factors on the growth of the strain,under the optimal conditions of BD,FR two strains of crude oil degradation ability determination of the characteristics of the strain.The results showed that the optimum salinity of strain BD was 0.1%.The optimum salinity of FR is 0.5%,and FR is difficult to grow when salinity exceeds 2%,and BD has a wider tolerance range to salinity.Both strains showed the highest biomass at PH of 7,and THE FR strain still had good biomass in a slightly alkaline environment,indicating that FR could withstand a certain alkaline environment.The optimum temperature of strain FR was about 29?.The optimum temperature of strain BD was 34?.Both strains grew well in the range of 18? to 42?,and FR had better ability to adapt to high and low temperature environment.The optimal crude oil concentration of strain BD was 300mg/L,and the optimal crude oil concentration of strain FR was 500mg/L.When the crude oil concentration was greater than 500mg/L,the biomass of both strains decreased with the increase of crude oil concentration.The FR biomass of the strain was less affected by the increase of crude oil concentration,and it showed a strong pollutant tolerance ability.The FR biomass of the strain was still as high as 0.65 when the crude oil concentration was 4000mg/L,so it was speculated that its high tolerance to crude oil was related to the special cellular structure of bacillus.The delay period of FR is shorter than that of BD with stronger environmental adaptability,and higher biomass and crude oil degradation rate can be obtained at the initial stage of reinoculation.The crude oil degradation rates of BD and FR strains were 38.72% and 42.95% respectively after being shaken for 25 days under their own optimal environmental conditions.Crude oil degrades well.