Fig. 7

Trans-domain relationships between archaea and bacteria in the gut. a Fecal archaea-to-bacteria abundance ratio across populations in association with ethnicity and rural versus urban residency. Across-population comparisons were conducted between the base mean of group of interest and that of all groups, statistical significance was determined by Wilcoxon rank sum test with Holm-Bonferroni adjustment of p values, ^$$$p < 0.001, ^$$$$p < 0.0001. Statistical significance between rural and urban populations for each individual ethnicity was determined by Mann-Whitney test, **p < 0.01, ****p < 0.0001. b Correlations between the species diversity and richness of the gut archaeome and bacteriome. Pearson correlation tests were performed for coefficient estimation and statistical significance determination, *p < 0.05. c, d Between-microbial species correlations were calculated via SparCC. Only those correlations with |correlation coefficient| > 0.1 and statistical significance (FDR adjusted p < 0.05) were plotted and visualized via Cytoscape. Each node denotes a microbial species and color-coated according to its taxonomic domain of archaea (darkred) or bacteria (darkgreen). The node size is proportional to the degree of its connectivity to other nodes. Specific microbial species associated with M. smithii were plotted in d for easier visualization. The connection lines between nodes were color-coated according to correlation direction (positive or negative) and were color-intensified according to coefficient size