Degradation of TCE Enhanced Using Phytoremediation

By: Leslie Romero

Trichloroethylene (TCE) is a common organic environmental pollutant found in groundwater, also known to be a human carcinogen. This contamination is associated with its improper disposal and spills. Due to its contamination prevalence, it has been a priority for the United States Environmental Protection Agency to find effective methods to decrease the contamination. To approach the situation, phytoremediation may be used as a cheaper alternative by using the ability of plants to take up chemicals from water and soils through its root system to degrade pollutants. For the most part, plants use their symbiotic relationships with internal microorganisms (endophytes) to adapt to environmental changes and degrade pollutants. Some plant species can recruit more beneficial microorganisms than others, suggesting the effect to be plant genotype-specific. To further study this remediation by using endophytes, a natural bacterial endophyte, Enterobacter sp. strain PDN3, was isolated and characterized from poplar trees. After a three-year field trial, inoculated poplar trees demonstrated a growth increase and reduced TCE phytotoxic effects. These trees expelled 50% more chloride ion, indicating towards an increase of TCE metabolism in plants. These findings suggest phytoremediation can be used as a cost-effective approach for degradation TCE, or even other pollutants. 

                 
                      

                                Figure 1. Phytoremediation process. Photo credit: http://pubs.sciepub.com/ijebb/2/4/5/

Original Article: Enhanced Degradation of TCE on a Superfund Site Using Endophyte-Assisted Poplar Tree Phytoremediation. Sharon L. Doty, John L. Freeman, Christopher M. Cohu, Joel G. Burken, Andrea Firrincieli, Andrew Simon, Zareen Khan, J. G. Isebrands, Joseph Lukas, and Michael J. Blaylock. Environmental Science & Technology. 2017. 51 (17)

Tracing the Steps of a Deathly Pathogen

Listeria monocytogenes is a deathly, pathogenic bacterium that can cause Listeriosis in humans. Listeriosis is a foodborne disease with a high mortality rate, and birth defects in the cases of pregnant patients. However, recent research has found that this bacterium can replicate in the murine gall bladder, and that its replication is extracellular and intraluminal. These findings were supported by extensive research done on Balb/c mice, by injecting them with two L.monocytogenes strains (10403S and LM23074) that were made luminescent with the help of chromosomal integration of a lux-kan transposon. The mice were either orally or intravenously infected with the L.monocytogenes strains to observe bacterial activity in vivo through bioluminescent images. After dissection, researchers recovered virulent strains only from the murine gall bladder, which prompted them to further investigate luminal contents of the gall bladder. As a result, they found that the bacterium could replicate extracellularly in the lumen of the gall bladder in living mice. This is important because it can lead to more safe treatment options for Listeriosis, specifically for pregnant women.

A.) Infected mouse on day 3. B.) Luminal contents of the gall bladder. C.) Bioluminscent colonies recovered from the infected gall bladder. D.) Tissue Gram stain of an infected gall bladder of a mouse. Image retrieved from article (Hardy et al., 2004).

Hardy J., Francis K.P., DeBoer M., Chu P., Gibbs K. and Contag C.H. (2004). “Extracellular Replication of Listeria Monocytogenes in the Murine Gall Bladder,” Science (New York, N.Y.), 303(5659), pp. 851–3.