Abstract
Soils co-contaminated with metals and organics present special problems for remediation. Metal contamination can delay or inhibit microbial degradation of organic pollutants such that for effective in situ biodegradation, bioaugmentation is necessary. We monitored the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) or 3-chlorobenzoate (3-CB) in two different soils with and without cadmium (Cd) contamination. Additionally, we evaluated the ability of bioaugmentation to enhance organic degradation in these co-contaminated soils. Finally, we determined whether enhanced degradation was due to survival of the introduced organism (cell bioaugmentation) or plasmid transfer to indigenous microbial populations (gene bioaugmentation). In Brazito soil, dual inoculation with a Cd-resistant bacterium plus a known 2,4-D-degrading bacterium, Ralstonia eutropha JMP134, enhanced 2,4-D degradation. Escherichia coli D11, which lacks chromosomal genes necessary for complete 2,4-D mineralization, was used for gene bioaugmentation in Madera soil. Significant gene transfer of the plasmid to the indigenous populations was observed, and the rate of 2,4-D degradation was enhanced relative to that of controls. Cell bioaugmentation was further demonstrated when (Comamonas testosteroni was used to enhance biodegradation of 3-CB in Madera soil. In this case no transfer of plasmid pBRC60 to indigenous soil recipients was observed. For the Madera soil, nonbioaugmented samples ultimately showed complete 2,4-D degradation. In contrast, nonbioaugmented Brazito soils showed incomplete 2,4-D degradation. These studies are unique in showing that both cell bioaugmentation and gene bioaugmentation can be effective in enhancing organic degradation in co-contaminated soils. Ultimately, the bioaugmentation strategy may depend on the degree of contamination and the time frame available for remediation.
Full Text
The Full Text of this article is available as a PDF (149.0 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Fulthorpe R. R., Rhodes A. N., Tiedje J. M. Pristine soils mineralize 3-chlorobenzoate and 2,4-dichlorophenoxyacetate via different microbial populations. Appl Environ Microbiol. 1996 Apr;62(4):1159–1166. doi: 10.1128/aem.62.4.1159-1166.1996. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gentry T. J., Newby D. T., Josephson K. L., Pepper I. L. Soil microbial population dynamics following bioaugmentation with a 3-chlorobenzoate-degrading bacterial culture. Bioaugmentation effects on soil microorganisms. Biodegradation. 2001;12(5):349–357. doi: 10.1023/a:1014394709703. [DOI] [PubMed] [Google Scholar]
- Naidu C. K., Reddy T. K. Effect of cadmium on microorganisms and microbe-mediated mineralization process in the soil. Bull Environ Contam Toxicol. 1988 Nov;41(5):657–663. doi: 10.1007/BF02021015. [DOI] [PubMed] [Google Scholar]
- Nakatsu C. H., Providenti M., Wyndham R. C. The cis-diol dehydrogenase cbaC gene of Tn5271 is required for growth on 3-chlorobenzoate but not 3,4-dichlorobenzoate. Gene. 1997 Sep 1;196(1-2):209–218. doi: 10.1016/s0378-1119(97)00229-1. [DOI] [PubMed] [Google Scholar]
- Neilson J. W., Josephson K. L., Pepper I. L., Arnold R. B., Di Giovanni G. D., Sinclair N. A. Frequency of horizontal gene transfer of a large catabolic plasmid (pJP4) in soil. Appl Environ Microbiol. 1994 Nov;60(11):4053–4058. doi: 10.1128/aem.60.11.4053-4058.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Newby D. T., Gentry T. J., Pepper I. L. Comparison of 2,4-dichlorophenoxyacetic acid degradation and plasmid transfer in soil resulting from bioaugmentation with two different pJP4 donors. Appl Environ Microbiol. 2000 Aug;66(8):3399–3407. doi: 10.1128/aem.66.8.3399-3407.2000. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Newby D. T., Josephson K. L., Pepper I. L. Detection and characterization of plasmid pJP4 transfer to indigenous soil bacteria. Appl Environ Microbiol. 2000 Jan;66(1):290–296. doi: 10.1128/aem.66.1.290-296.2000. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roane T. M., Josephson K. L., Pepper I. L. Dual-bioaugmentation strategy to enhance remediation of cocontaminated soil. Appl Environ Microbiol. 2001 Jul;67(7):3208–3215. doi: 10.1128/AEM.67.7.3208-3215.2001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roane TM, Pepper IL. Microbial Responses to Environmentally Toxic Cadmium. Microb Ecol. 1999 Nov;38(4):358–364. doi: 10.1007/s002489901001. [DOI] [PubMed] [Google Scholar]
- Versalovic J., Koeuth T., Lupski J. R. Distribution of repetitive DNA sequences in eubacteria and application to fingerprinting of bacterial genomes. Nucleic Acids Res. 1991 Dec 25;19(24):6823–6831. doi: 10.1093/nar/19.24.6823. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wyndham R. C., Singh R. K., Straus N. A. Catabolic instability, plasmid gene deletion and recombination in Alcaligenes sp. BR60. Arch Microbiol. 1988;150(3):237–243. doi: 10.1007/BF00407786. [DOI] [PubMed] [Google Scholar]