Ji X, Ripp S, Layton AC, Sayler GS, DeBruyn JM
Environmental contamination by organics such as polycyclic aromatic hydrocarbons (PAHs) generally changes
native microbial communities. However our understanding of microbial responses has been limited to short term
studies (i.e., less than 2-3 years) so long term community responses are not as well understood. In 1996, the
genetically engineered microorganism Pseudomonas fluorescens HK44 was released into polycyclic aromatic
hydrocarbon (PAH)-contaminated soil in lysimeters to monitor in situ PAH-biodegradation.
The objective of this study was to assess the long term impacts of PAH contamination and addition of HK44 on the
indigenous soil bacterial community structure. In 2010, 14 years after the lysimeter experiment initiation, lysimeters
were unsealed and sampled. Although PAHs were degraded and PAH concentrations fell below detectable levels
within approximately the first two years of this experiment, lysimeters that had received PAHs had significantly higher
soil organic matter content (1.30 ± 0.23%) than control lysimeters with clean soils (0.81 ± 0.08%). Pyrosequencing
of 16S rRNA gene amplicon libraries revealed a distinct bacterial community structure in the lysimeters that had
received PAHs. In contrast, there were no discernible differences in soil chemistry or bacterial community structures
in lysimeters where HK44 was inoculated compared to those to which HK44 was not inoculated. These results
indicate that although the initial perturbations are no longer detectable, the addition of PAHs had long term influences
on the bacterial communities, while the introduction of the genetically engineered microorganism HK44 did not.
Ji X, Ripp S, Layton AC, Sayler GS, DeBruyn JM. 2013. Assessing long term effects of bioremediation: Soil bacterial communities 14 years after polycyclic aromatic hydrocarbon contamination and introduction of a genetically engineered microorganism. OMICS Journal of Bioremediation and Biodegradation 4:e209, doi: 10.4172/2155-6199.1000209.