Fig. 2: Bacterial load and community composition differ between foragers, nurses, and winter bees across 14 colonies.

a Average 16S rRNA gene copy number per gut in foragers, nurses, and winter bees as determined from the pooled gut samples from 14 different colonies. b Differences in α-diversity, i.e., effective number of species, in the gut microbiota of foragers, nurses, and winter bees based on 16S rRNA gene amplicon sequencing. c NMDS based on Bray–Curtis dissimilarities on the gut communities of foragers, nurses, and winter bees based on 16S rRNA gene amplicon sequencing. d Relative community composition of the gut microbiota as determined by 16S rRNA gene amplicon sequencing. The seven phylotypes monitored by qPCR (see Fig. 1 and Supplementary Fig. S4), making up the vast majority of the community, are highlighted by a gray box in the legend. Capital letters below the stacked bars indicate the hive of origin. e Absolute abundance of each of the seven major phylotypes in foragers (F), nurses (N), and winter bees (W) across hives, as determined based on the number of genome equivalents per gut calculated by multiplying the relative abundance of each phylotype by the total 16S rRNA gene copy number. f Absolute abundance of a subset of the minor community members in foragers (F), nurses (N), and winter bees (W) across hives, as determined based on the number of genome equivalents per gut calculated by multiplying the relative abundance of each phylotype by the total 16S rRNA gene copy number. <LOD, below limit of detection of the 16S rRNA amplicon sequencing, i.e., no reads were obtained for that particular taxa in the respective sample. Mean values for the samples above the LOD are shown as black horizontal lines. Absolute abundance of the remaining phylotypes is depicted in Supplementary Fig. S4b. In a, b, e, f levels (bee types) not connected by the same letter are significantly different as based on ANOVA followed by Tukey’s HSD test (see Supplementary Table S3).