Direct molecular biological analysis of ammonia oxidising bacteria populations in cultivated soil plots treated with swine manure
1997
Hastings, R.C. | Ceccherini, M.T. | Miclaus, N. | Saunders, J.R. | Bazzicalupo, M. | McCarthy, A.J.
The application of pig slurry, high in ammonia-nitrogen concentration, to agricultural land is a practice whose effect on soil microbial communities is poorly understood. The autotrophic ammonia-oxidising bacteria are an integral component of the nitrogen cycle in soil and their activity will be affected by addition of nitrogenous fertilizer. Molecular biological techniques were applied to the direct detection and identification of ammonia-oxidiser populations in cultivated soil plots treated with different amounts of pig slurry. Members of the genus Nitrosospira were shown by 16S rDNA-directed PCR to be present in both unamended and amended soils, regardless of the quantity of pig slurry applied. In contrast, members of the genus Nitrosomonas were detected by the same approach only in those soil plots that had received high loadings of slurry. The fidelity of amplification products was always confirmed by oligonucleotide probing. In addition, we used high stringency PCR and confirmatory gene probing to detect the presence of the ammonia monooxygenase gene (amoA) of Nitrosomonas europaea directly in all amended soil samples, with hybridization signal intensities that increased with the amount of pig slurry applied to plots. Nitrosomonas europaea amoA DNA could not be detected in soil from the untreated plot. These data support the view that nitrosospiras are ubiquitous as important members of nitrifying populations in the environment. The direct detection of nitrosomonad DNA only in amended soils supports the hypothesis that these nitrosomonads become highly competitive under conditions analogous to laboratory enrichment cultures.
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