Effect of toxic metals on indigenous soil {beta}-subgroup proteobacterium ammonia oxidizer community structure and protection against toxicity by inoculated metal-resistant bacteria
- Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology
- Netherlands Inst. of Ecology, Heteren (Netherlands)
Contamination of soils with toxic metals is a major problem on military, industrial, and mining sites worldwide. Of particular interest to the field of bioremediation is the selection of biological markers for the end point of remediation. In this microcosm study, the authors focus on the effect of addition of a mixture of toxic metals (cadmium, cobalt, cesium, and strontium as chlorides) to soil on the population structure and size of the ammonia, oxidizers that are members of the beta subgroup of the Proteobacteria. In a parallel experiment, the soils were also treated by the addition of five strains of metal-resistant heterotrophic bacteria. Effects on nitrogen cycling were measured by monitoring the NH{sub 3} and NH{sub 4}{sup +} levels in soil samples. The gene encoding the {alpha}-subunit of ammonia monooxygenase (amoA) was selected as a functional molecular marker for the {beta}-subgroup ammonia oxidizing bacteria. Community structure comparisons were performed with clone libraries of PCR-amplified fragments of amoA recovered from contaminated and control microcosms for 8 weeks. Analysis was performed by restriction digestion and sequence comparison. The abundance of ammonia oxidizers in these microcosms was also monitored by competitive PCR. All amoA gene fragments recovered grouped with sequences derived from cultured Nitrosospira. These comprised four novel sequence clusters and a single unique clone. Specific changes in the community structure of {beta}-subgroup ammonia oxidizers were associated with the addition of metals. These changes were not seen in the presence of the inoculated metal-resistant bacteria. Neither treatment significantly altered the total number of {beta}-subgroup ammonia-oxidizing cells per gram of soil compared to untreated controls. Following an initial decrease in concentration, ammonia began to accumulate in metal-treated soils toward the end of the experiment.
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- FC02-96ER62278
- OSTI ID:
- 318779
- Journal Information:
- Applied and Environmental Microbiology, Vol. 65, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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