Explorative meta-analysis of 417 extant archaeal genomes to predict their contribution to the total microbiome functionality

Abstract

Unveiling the relationship between taxonomy and function in microbiomes is crucial to determine their contribution to ecosystem functioning. However, while the relationship between taxonomic and functional diversity in bacteria and fungi was reported, this is not the case for archaea. Here, we used a meta-analysis of completely annotated extant genomes of 417 taxonomically unique archaeal species to describe intergenome and intragenome redundancy of functions and to predict the extent of microbiome functionality on Earth contained within archaeal genomes using accumulation curves of all known functions from the level 3 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 trade of 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 potential of bacteria and fungi. Using a global archaeal species richness estimate of 13,159, the logarithmic model predicts a total of 4,164.1 {+/-}2.9 KEGG level 3 functions while the non-parametric bootstrap estimate yields a lower bound of 2,994 {+/-}57 KEGG level 3 functions. Our approach not only highlights similarities in functional redundancy but also the difference in functional potential of archaea compared to other domains of life.