Curiel Yuste J., Fernandez-Gonzalez A.J., Fernandez-Lopez M., Ogaya R., Penuelas J., Lloret F. (2014) Functional diversification within bacterial lineages promotes wide functional overlapping between taxonomic groups in a Mediterranean forest soil. FEMS Microbiology Ecology. : 0-0.EnllaçDoi: 10.1111/1574-6941.12373
We investigated the relationship between taxonomy and functioning of soil bacterial communities in soils from a Mediterranean holm oak forest using a high-throughput DNA pyrosequencing technique. We used nonparametric tests (Mann-Whitney U-test) to evaluate the sensitivity of each single bacterial genus within the community to the fluctuations of plant physiological and environmental abiotic variables, as well as to fluctuations in soil microbial respiration. Within-lineage (phylum/class) functional similarities were evaluated by the distribution of the Mann-Whitney U-test standardized coefficients (z) obtained for all genera within a given lineage. We further defined different ecological niches and within-lineage degree of functional diversification based on multivariate analyses (principal component analyses, PCA). Our results indicate that strong within-lineage functional diversification causes extensive functional overlapping between lineages, which hinders the translation of taxonomic diversity into a meaningful functional classification of bacteria. Our results further suggest a widespread colonization of possible ecological niches as taxonomic diversity increases. While no strong functional differentiation could be drawn from the analyses at the phylum/class level, our results suggest a strong ecological niche differentiation of bacteria based mainly on the distinct response of Gram-positive and Gram-negative bacteria to fluctuations in soil moisture. We investigated the relation between taxonomy and functioning of soil bacterial communities in soils from a Mediterranean Holm-oak forest using a high throughput DNA pyrosequencing technique. © 2014 Federation of European Microbiological Societies.
Curiel Yuste J., Fernandez-Gonzalez A.J., Fernandez-Lopez M., Ogaya R., Penuelas J., Sardans J., Lloret F. (2014) Strong functional stability of soil microbial communities under semiarid Mediterranean conditions and subjected to long-term shifts in baseline precipitation. Soil Biology and Biochemistry. 69: 223-233.EnllaçDoi: 10.1016/j.soilbio.2013.10.045
We investigated the effect of soil microclimate on the structure and functioning of soil microbial communities in a Mediterranean Holm-oak forest subjected to 10 years of partial rain exclusion manipulations, simulating average drought conditions expected in Mediterranean areas for the following decades. We applied a high throughput DNA pyrosequencing technique coupled to parallel measurements of microbial respiration (RH) and temperature sensitivity of microbial respiration (Q10). Some consistent changes in the structure of bacterial communities suggest a slow process of community shifts parallel to the trend towards oligotrophy in response to long-term droughts. However, the structure of bacterial communities was mainly determined by short-term environmental fluctuations associated with sampling date (winter, spring and summer) rather than long-term (10 years) shifts in baseline precipitation. Moreover, long-term drought did not exert any chronic effect on the functioning of soil microbial communities (RH and Q10), emphasizing the functional stability of these communities to this long-term but mild shifts in water availability. We hypothesize that the particular conditions of the Mediterranean climate with strong seasonal shifts in both temperature and soil water availability but also characterized by very extreme environmental conditions during summer, was acting as a strong force in community assembling, selecting phenotypes adapted to the semiarid conditions characterizing Mediterranean ecosystems. Relations of climate with the phylogenetic structure and overall diversity of the communities as well as the distribution of the individual responses of different lineages (genera) to climate confirmed our hypotheses, evidencing communities dominated by thermotolerant and drought-tolerant phenotypes. © 2013 Elsevier Ltd.
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