『Abstract
　Marine waters are most vulnerable to crude oil pollution due to increased sea-based oil-related activities. Successful remediation of such polluted environments is normally carried out in a laboratory with suitable physical and environmental alterations. However, it is challenging to alter the physical and environmental conditions in crude oil-contaminated natural environments. In a previous study, six hydrocarbonoclastic bacteria were isolated from an oil-contaminated site. Here we report on their ability to mineralise weathered crude oil as a carbon source in seawater mesocosms, in order to construct a hydrocarbonoclastic consortia for the effective mineralisation of hydrocarbons present in the weathered crude oil at seawater-based environment. This was completed without altering the physical and environmental parameters (salinity, pH and temperature) and followed by the detection of microbial community changes. The total amount of oil mineralised by these six isolates individually over 28-day incubation ranged from 4.7 to 10%. The bacterial consortia composed of these six strains showed a greater mineralisation rate (18.5 %). Temperature gradient gel electrophoresis revealed that the functionally dominant species were present after the first week (week 2 to week 4) following the addition of the consortia, which were represented in dendrogram by cluster 2 and also these weeks representing a distinct point on the Pareto-Lorenz curve; no community could be identified in controls in which no consortia were added. This shows that the addition of consortia potentially deal with changing environmental conditions and preserved its functionality followed by effective mineralisation of weathered crude oil.

Keywords: Hydrocarbonoclastic bacteria; Mesocosms; Mineralisation; Pareto-Lorenz curve; Temperature gradient gel Electrophoresis (TGGE); Weathered crude oil』

1. Introduction
2. Materials and methods
　2.1. Growth of bacteria on crude oil
　2.2. Nucleic acid extraction
　2.3. Bacterial 16 S rDNA amplification
　2.4. Identification of hydrocarbonoclastic bacterial species
　2.5. Individual mesocosm system
　2.6. Consortia mesocosm system
　2.7. Respiratory measurements in mesocosms
　2.8. Determination of total petroleum hydrocarbons of aromatics and aliphatics
　2.9. Temperature gradient gel electrophoresis
　2.10. Statistical analyses
3. Results
　3.1. GC analysis of crude oil and seawater used in each treatment during the incubation of the mesocosms
　3.2. Microbial community changes
　3.3. Pareto-Lorenz curve
4. Discussion
Acknowledgments
References