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Revealing the relationship between taxonomy and function in microbiomes is critical to discover their contribution to ecosystem functioning. However, while the relationship between taxonomic and functional diversity in bacteria and fungi is known, this is not the case for archaea. Here, we used a meta-analysis of 417 completely annotated extant and taxonomically unique archaeal genomes to predict the extent of microbiome functionality on Earth contained within archaeal genomes using accumulation curves of all known level 3 functions of KEGG Orthology. We found that intergenome redundancy as functions present in multiple genomes was inversely related to intragenome redundancy as multiple copies of a gene in one genome, implying the tradeoff between additional copies of functionally important genes or a higher number of different genes. A logarithmic model described the relationship between functional diversity and species richness better than both the unsaturated and the saturated model, which suggests a limited total number of archaeal functions in contrast to the sheer unlimited potential of bacteria and fungi. Using the global archaeal species richness estimate of 13,159, the logarithmic model predicted 4164.1 ± 2.9 KEGG level 3 functions. The non-parametric bootstrap estimate yielded a lower bound of 2994 ± 57 KEGG level 3 functions. Our approach not only highlighted similarities in functional redundancy but also the difference in functional potential of archaea compared to other domains of life. [ABSTRACT FROM AUTHOR]

Despite being well adapted to the long seasonal droughts of the Mediterranean Basin, the holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.) has undergone a gradual decline during the last decades. The reasons of this decline are not fully understood, but evidence suggests that the quality and quantity of the interactions of holm oaks with the soil microbiota are playing a central role in the resilience of this species. With the aim to test the previous statement as our hypothesis, 9 oak savannah sites (called dehesas from here on) were sampled, in which asymptomatic (healthy) and symptomatic (early stage of decline) trees were interspersed. Using high throughput amplicon sequencing, soil bacterial and fungal biota (called soil microbiota from here on) were sequenced. Our results showed that soil fungal community composition differed between healthy and declining trees whereas bacterial communities did not show significant differences. Specifically, the degree of holm-oak defoliation was negatively correlated to the relative abundance of ectomycorrhizal (ECM) fungi and fungal endophytes, suggesting a relation between trees' health and soil fungal symbionts. Although our observational study cannot give a final answer to the directionality of the relationships observed, our results support the idea that small changes in symbiont abundance might be causing holm oaks to lose their ability to withstand the strong environmental pressures. • Microbial soil diversity correlates with tree health status. • Fungal diversity is more related to tree health than bacterial diversity. • The abundance of ectomycorrhiza (ECM) and fungal endophytes is related to tree resilience. • Small spatial variability in plant-fungal symbiotic relations influences tree health. [ABSTRACT FROM AUTHOR]