Analysis Of Bacterial Community And Characteristics Of Diesel Degrading Bacteria In Islands Area Of The South China Sea

The South China Sea is the largest sea area in China,which has abundant microbial resources.The islands in the South China Sea are considered as the martime land.And the water is at a high risk of oil pollution due to the frequent sailing of ships.Microbial degradation is one of the important methods to remove oil pollution.At present,there is limited understanding of the characteristics of bacterial communities in the South China Sea island areas and there are few researches on oil degrading bacteria.In this study,the surface seawater of the South China Sea island areas was selected as the research object,and the bacterial community structure and metabolic characteristics were analyzed by the oligotrophic culture method,and the species distribution of potential oil degrading bacteria was explored.Using diesel oil as the only carbon source,oil degrading bacteria were enriched and separated.Then,the separated diesel degrading bacteria were identified by molecular biology.The preliminary screening and re-screening were carried out according to their diesel degrading ability to obtain a high-efficiency diesel degrading bacteria.Additionally,the effects of different initial p H,salinity,temperature and initial bacterial concentration on the growth and degradation ability of this strain were also studied.Through this study,it is expected to clarify the characteristics of bacterial communities in the waters of isalnds in the South China Sea and provide high-quality bacterial resources for oil pollution bioremediation.The research results are as follows:1)After 15 days of resuscitation culture,the structures of the bacterial communities in the South China Sea island areas were analyzed based on the 16S sequencing results.Bacteria of 15 phyla,36 classes and 236 genera were detected in island area of Y1,bacteria of 14 phyla,31 classes and 229 genera were detected in island area of Y2,and bacteria of12 phyla,26 classes and 166 genera were detected in island area of Y3.Synthetically,a total of 19 genera of bacteria were detected as potential oil-degrading bacteria in three island areas.Based on the culturable system,4 phyla and 9 genera were separated and purified from group Y1,with a total of 12 strains of bacteria.2 phyla and 8 genera were separated and purified from group Y2,with a total of 14 strains.2 phyla and 3 genera were separated and purified from group Y3,with a total of 15 strains.Among the dominant bacteria from the three island areas,a total of 30 strains of 7 genera may be potential oil-degrading bacteria.The degree of carbon source utilization of bacteria in the waters of the three island areas is ranked as follows:carbohydrates>carboxylic acids>amino acids>polymers>others>amines.2)Water samples in the South China Sea island areas were collected as the research object,and diesel was taken as the only carbon source.The diesel-degrading bacteria in these samples were enriched and cultivated,and a total of 24 strains of bacteria strains were separated.According to the molecular biology identification results,the 24 strains of bacteria were categorized into Acinetobacter,Alcanivorax,Halomonas,Ochrobactrum and Marinobacter.A strain of S₁4-1(Acinetobacter sp.)with the best diesel oil degradation ability was obtained by preliminary screening and re-screening for the 24 isolated strains.The maximum degradation rate of S₁4-1 reached 91.13%.Compared with the diesel concentration of 6 127.94 mg/L in the control group,the diesel concentration of S₁4-1 was only 543.62 mg/L after 7 days,with a degradation amount of 558.43 mg.Consequently,this study further explored the degradation characteristics of S₁4-1.3)The effects of different initial p H values,salinity,temperature and initial bacterial concentration on the growth and degradation capacity of strain S₁4-1 were analyzed.The results showed that the initial p H value had a significant effect on the growth and diesel oil degradation capacity of S₁4-1.Within the p H range of 6 to 10,this strain grew well In the case of the optimal p H of 8,the concentration of diesel oil decreased from 7 389.02 mg/L to 494.63 mg/L after 7 days.Compared with the control group,the maximum degradation rate reached 93.30%,and the maximum degradation amount of diesel oil was 615.79 mg.Salinity has little effect on the growth and diesel degradation ability of the strain.The strain grew well in the salinity range of 20 to 40.In the case of the optimal salinity of 30,the concentration of diesel oil decreased from 6 939.46 mg/L to 300.34 mg/L after 7 days.Compared with the control group,the maximum degradation rate was 96.00%,and the maximum degradation amount was 617.09 mg.The growth and diesel degradation ability of strain S₁4-1 were greatly affected by temperature.It grew well in the temperature range of 20?to 30?,and in the case of the optimal temperature of 30?,the concentration of diesel oil decreased from 7 638.71 mg/L to 332.26 mg/L after 7 days.Compared with the control group,the maximum degradation rate was 95.47%,and the maximum degradation amount of diesel oil was 631.88 mg.There was no significant difference in the bacterial biomass and degradation rate on the 7^thday within the initial concentration of 10⁴to 10⁷CFU/m L(P>0.05).After 7 days,the concentration of diesel oil decreased to 350.98 mg/L,the maximum degradation rate was above 94.73%,and the maximum degradation amount was above 631.32 mg.In conclusion,under the conditions of initial p H of 8,salinity of 30,temperature of 30?,and initial concentration of 10⁴CFU/m L-10⁷CFU/m L,strain S₁4-1had a good degradation effect on diesel oil,and the degradation rate reached 97.11%and the degradation amount reached 647.13 mg after 7 days.