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 disturbed with solid 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 if the indigenous bacterial community would possess the complexity commonly observed for natural soils, and thus may limit potential for remediating the site using monitored 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 30 m), which also contained greater concentrations of organic carbon. General diversity patterns were dominated by the phylum Proteobacteria (λ, β, and α 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. (λ-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 has a very important role in the community.
Bibliographical noteFunding Information:
The authors thank Moisés Posada, Lynn Connor and Terry Holman for laboratory assistance and Dr. Angela Kent for computing support and advising. This work was supported by The Urban development Office and The Metropolitan Area in Medellín, Colombia, The Agricultural Research Service, United States Department of Agriculture, project number 3611-12220-006-00D and a grant provided by the American Society for Microbiology and its international fellowship program for Latin America and the Caribbean. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the United States Department of Agriculture, University of Illinois, or The National University of Colombia.
Copyright 2011 Elsevier B.V., All rights reserved.
- Bacterial diversity
- Hydrocarbon degradation
- Ribosomal intergenic spacer analysis
- Solid waste dump/landfill
- Temporal temperature gel electrophoresis
- Terminal restriction fragment length polymorphism