Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGY, MANAGEMENT AND ENVIRONMENTAL IMPACT OF WEEDY AND INVASIVE PLANT SPECIES IN A CHANGING CLIMATE

Location: Global Change and Photosynthesis Research Unit

Title: Characterization of bacterial diversity at different depths in the Moravia Hill landfill site at Medellin, Colombia

Authors
item Gomez, Andres -
item Yannarell, Anthony -
item Sims, Gerald
item Resterpo, Gloria -
item Moreno, Claudia -

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2011
Publication Date: March 11, 2011
Citation: Gomez, A.M., Yannarell, A.C., Sims, G.K., Resterpo, G.C., Moreno, C.X. 2011. Characterization of bacterial diversity at different depths in the Moravia Hill landfill site at Medellin, Colombia. Soil Biology and Biochemistry. 43:1275-1284.

Interpretive Summary: Bacterial diversity was examined at different depths within a former solid waste dump in Medellín, Colombia. Sampling sites included a densely populated area, which is built upon 40 meters of solid waste (domestic, industrial, agricultural, and medical).The soil and leachate contain high levels of contaminants and the natural soil is diluted with man-made materials, disrupting natural aggregation and resulting in a loose, porous matrix with irregular aggregate structure. The unusual physical structure and contaminant levels at the site were potential obstacles for indigenous bacteria to remediate contamination at the site by natural biodegradation. Bacterial diversity patterns were determined through a variety of molecular biology and traditional microbiology techniques at depths of 0, 10, 20 and 30 meters. Abundance and diversity patterns varied among the four different depths, showing more complex patterns in deeper samples (20 and 30m), which also contained greater concentrations of organic matter. General diversity patterns were dominated by specific organsisms (especially, members of the phylum Proteobacteria).These findings were reinforced by analysis of the culturable fraction able to use the model polutant, n-hexadecane as a sole carbon source, in which the genus Acinetobacter was dominant. This research offers new clues regarding bacterial diversity patterns through different depths in polluted environments with unique physicochemical conditions, suggesting that bacterial diversity profiles may be highly influenced by the nature of pollutants present. Moreover, the findings show that buried organic materials (which also occur naturally in some soils) can drive elevated levels of microbial diversity well below the soil surface. This may explain the occurrence of subsurface microbial degradation products in paleosols (fossil soils found buried within sedimentary) sometimes found in agricultural areas where they may exaggerate the degree of nutrient leaching occurring at the site. The impact of this research is to demonstrate approaches required to verify the origin of microbial byproducts occurring at depth.

Technical Abstract: A combination of culture-dependent and culture-independent methods was used to assess bacterial diversity at different depths within a former solid waste dump in Medellín, Colombia. Sampling sites included a densely populated area, which is built upon 40 m of solid waste (domestic, industrial, agricultural, and medical). The soil and leachate contain high levels of contaminants and the natural soil is highly diluted with anthropogenic materials, disrupting natural aggregation and resulting in a loose, porous matrix with irregular aggregate structure. The unusual physical structure and contaminant levels at the site made it unclear that the indigenous bacterial community would possess the complexity commonly observed for natural soils, and thus may limit potential for remediating the site using natural attenuation. Bacterial diversity patterns were determined through 16S-TTGE and T-RFLP at depths of 0, 10, 20 and 30 m. Abundance and diversity patterns, as estimated by number and intensity of terminal restriction fragments and TTGE bands, varied among the 4 different depths, showing more complex patterns in deeper samples (20 and 30m), which also contained greater concentrations of organic carbon. General diversity patterns were dominated by the phylum Proteobacteria (alpha, beta, and gamma divisions). These findings were reinforced by analysis of the culturable fraction able to use n-hexadecane as sole carbon source, in which the genera Acinetobacter sp. (gamma Proteobacteria) was dominant. This research offers new clues regarding bacterial diversity patterns through different depths in polluted environments with unique physicochemical conditions, suggesting that bacterial diversity profiles may be highly influenced by the nature of pollutants present. Additionally, results imply that the culturable fraction at the site might be dominant over their uncultured counterparts.

Last Modified: 12/21/2014
Footer Content Back to Top of Page