Phenanthrene mineralization by Pseudomonas sp. UG14

Area of Science:

• Environmental Microbiology
• Bioremediation
• Polycyclic Aromatic Hydrocarbon (PAH) Degradation

Background:

• Creosote contamination poses significant environmental challenges due to persistent polycyclic aromatic hydrocarbons (PAHs) like phenanthrene.
• Microbial degradation is a key strategy for remediating PAH-contaminated soils and water.

Purpose of the Study:

• To isolate and characterize a microorganism capable of mineralizing phenanthrene.
• To investigate the role of specific genes and plasmids in phenanthrene degradation.
• To evaluate the effect of biosurfactants on enhancing phenanthrene mineralization.

Main Methods:

• Isolation of phenanthrene-degrading bacteria from contaminated soil.
• Plasmid profiling and Southern hybridization to identify relevant genes (ndoB, xylE).
• Radiotracer experiments ([9-(14)C]phenanthrene) to quantify mineralization rates at various concentrations.
• Identification of metabolites using analytical techniques.
• Assessment of biosurfactant (rhamnolipid) enhancement of phenanthrene mineralization.

Main Results:

• A Pseudomonas sp. (UG14) capable of phenanthrene mineralization was isolated.
• UG14 possesses plasmids, with the smaller one containing genes homologous to ndoB and xylE, crucial for aromatic hydrocarbon catabolism.
• Mineralization efficiency decreased with increasing initial phenanthrene concentration (27% at 10 mg/l to 3.3% at 1000 mg/l).
• 1-hydroxy-2-naphthoic acid was identified as a major water-soluble metabolite.
• Rhamnolipid biosurfactants significantly enhanced phenanthrene mineralization by Pseudomonas sp. UG14, increasing it from 6.5% to 9.8% with increasing biosurfactant concentration.

Conclusions:

• Pseudomonas sp. UG14 is a promising candidate for phenanthrene bioremediation.
• The presence of specific catabolic genes on plasmids contributes to its degradation capabilities.
• Biosurfactant application can improve the efficiency of microbial phenanthrene degradation, highlighting a potential strategy for enhanced bioremediation of creosote-contaminated environments.