Fig. 3

Simplified biocrust foodweb for three dominant biocrust bacteria based on combining isolate exometabolomics data with in situ microbe–metabolite relationships. This network displays the relationships between metabolites and three dominant bacteria (or metabolically similar organisms) as they increase and decrease in relative abundance across wetting and successional stages in biocrust. The lower line plot corresponds to real relative abundance measurements for the three bacteria in level C successional stage biocrust. As Microcoleus sp. increases in relative abundance immediately after wetting, many metabolites released by the closest-related isolate are positively correlated with Microcoleus sp. in biocrust (solid red arrows) and as the two Bacilli increase in relative abundance (first Bacillus sp. 1 then Bacillus sp. 2), most metabolites consumed by the closest-related isolate decrease and are negatively correlated with these bacteria in biocrust (solid blue arrows) and most released metabolites are positively correlated (solid red arrows). Dotted arrows indicate metabolites that are released (red) or consumed (blue) by isolates, but did not display the expected relationship with that microorganism in situ. The thickness of the line corresponds to the absolute value of the Spearman’s rho correlation coefficient. The overall expected directionality (solid lines vs. dotted lines) was significant as determined by the exact binomial test (two-tailed p-value = 0.01). *FDR-adjusted p < 0.05 for individual microbe-metabolite Spearman correlations