Vertical transport of a field-released genetically engineered microorganism through soil

The vertical movement of a genetically-engineered bacterium released into a sub-surface soil contained within a lysimeter was investigated. The strain used was Pseudomonas fluorescens HK44, a lux-based microbe capable of bioremediating specific polyaromatic hydrocarbons (PAHs). Strain HK44 was inoculated into a 4 m deep by 2.5 m diameter soil lysimeter outfitted with a hydraulic assembly to control groundwater levels. After 230 days, the lysimeter was subjected to a water table manipulation that resulted in significant transport of HK44 cells to depths 60 cm below the original inoculation zone within 20 days. A lysimeter not exposed to water level fluctuations exhibited no significant vertical transport. These results demonstrate the potential distribution of genetically engineered microorganisms in subsurface soil due to groundwater effects.