Ammonia-oxidizing bacteria respond to multifactorial global change

Abstract

Recent studies have demonstrated that multiple co-occurring global changes can alter the abundance, diversity, and productivity of plant communities. Belowground processes, often mediated by soil microorganisms, are central to the response of these communities to global change. Very little is known, however, about the effects of multiple global changes on microbial communities. We examined the response of ammonia-oxidizing bacteria (AOB), microorganisms that mediate the transformation of ammonium into nitrite, to simultaneous increases in atmospheric CO 2, precipitation, temperature, and nitrogen deposition, manipulated on the ecosystem level in a California grassland. Both the community structure and abundance of AOB responded to these simulated global changes. Increased nitrogen deposition significantly altered the structure of the ammonia-oxidizing community, consistently shifting the community toward dominance by bacteria most closely related to Nitrosospira sp. 2. This shift was most pronounced when temperature and precipitation were not increased. Total abundance of AOB significantly decreased in response to increased atmospheric CO 2. This decrease was most pronounced when precipitation was also increased. Shifts in community composition were associated with increases in nitrification, but changes in abundance were not. These results demonstrate that microbial communities can be consistently altered by global changes and that these changes can have implications for ecosystem function.

The Biogeography of Ammonia-Oxidizing Bacterial Communities in Soil

“…An amoA-based survey may reveal more phylogenetic diversity (or at least more diversity at finer levels of taxonomic resolution) than our 16S rRNA-based survey, particularly considering that certain clusters of Nitrosospira can only be identified from amoA-based phylogenies [36]. However, although there are differences in methodological approaches and sequence analysis procedures that render direct comparisons difficult, a number of other studies have also found relatively low levels of sequence diversity in soil AOB communities [9,14,37,38].…”

“…However, while Nitrosopira cluster 2 was relatively abundant in three forest soil libraries (BF1, BZ2, BZ3) with reasonably low pHs (4.05-5.36), there was no overall correlation between the relative abundances of cluster 2 in the libraries and soil pH (ρ=0.15, P=0.3) suggesting that cluster 2 AOB do not necessarily have higher relative abundances in acidic soils. Likewise, results from previous studies [14][15][16]20] have contributed to the hypothesis that representatives of Nitrosospira cluster 3 are likely to be relatively more abundant in soils with higher levels of N availability. If we examine the proportional abundances of Nitrosospira cluster 3, we see no correlations with our measured indices of N availability (N mineralization rates and extractable NH 4 + or the sum of NH 4 + plus NO 3 − concentrations, P>0.4 in all cases).…”

“…We do know that distinct soils often harbor distinct AOB communities. A number of environmental factors, including vegetation type [9][10][11], soil nutrient levels [12][13][14][15][16], soil microclimate [13,17,18], and management practices [19][20][21], have been found to have an important influence on the spatial variability exhibited by AOB communities. However, because most studies have compared AOB communities across a rather limited number of samples, with one notable exception being the study by Avrahami and Conrad [18], it has been difficult to ascertain which soil biotic and abiotic characteristics are related to AOB community composition across larger spatial scales.…”

Nitrogen loading levels affect abundance and composition of soil ammonia oxidizing prokaryotes in semiarid temperate grassland

“…Another possibility is that the effect of high urea-N substrate addition on AOB and AOA predominated over the pH effect. Addition of N fertilizer showed no evidence for a community shift of AOB after 4 weeks (Avrahami et al 2002) or 6 weeks of incubation (Mendum et al 1999), but a shifts was observed after 16 weeks (Avrahami and Conrad 2003) and 2 years (Horz et al 2004). Our study provided convincing field experiment evidence for the effect of the relative long term of 6 years N loading levels on the soil ammonia oxidizing prokaryotes in the semiarid temperate grassland soils.…”

Abundance and community structure of ammonia oxidizing bacteria and archaea in a Sweden boreal forest soil under 19-year fertilization and 12-year warming

“…Given that soil microorganisms are the key drivers of soil nutrient cycling (e.g., Falkowski et al 2008), their roles in mediating climate change and ecosystem functioning are not well understood (Balser et al 2001). An increasing number of reports have revealed shifts of carbon (C) substrate availability to microorganisms with temperature variations (e.g., MacDonald et al 1995;Zogg et al 1997;Flury and Gessner 2010), but there has been a lack of studies regarding effects of global warming on N cyclingassociated microbes (Avrahami et al 2003;Horz et al 2004;Tourna et al 2008).…”