Gut microbiota structure differs between honey bees in winter and summer

Lucie Kešnerová; Olivier Emery; Michaël Troilo; Joanito Liberti; Berra Erkosar; Philipp Engel

Considering that the monitored phylotypes typically comprise the majority of the bacteria 322 present in the honey bee gut, we neglected the possible presence of additional, non-323 targeted members and analyzed the relative composition of the community based on our 324 data. In both years, the communities of winter bees were largely dominated by the 325 phylotypes Lactobacillus Firm-5 and Bartonella. In contrast, forager bees seem to have 326 more even community compositions (Fig. 1B) . The dominance of Lactobacillus Firm-5 and 327 Bartonella in winter bees was reflected by a reduction in a-diversity in winter bees 328 compared to foragers, as determined by the effective number of species (Fig. 1E , 329 Permutation T-Test, P=1e-4). Moreover, PCA revealed a clear separation between foragers 330 and winter bees (Fig. 1F, Lactobacillus Firm-5, Bartonella and Bifidobacterium, the four phylotypes with the largest 333 differences in abundance between the two types of bees (Fig. 1C) . 334 Taken together, these results suggest that the gut microbiota of winter bees and foragers 335 markedly differs from each other in the monitored hive, both in terms of the total bacterial 336 abundance and in the levels of individual microbiota members. 339 nurses, and winter bees across colonies 340 The observed differences in bacterial loads between foragers and winter bees in the 341 monitored hive prompted us to check for similar patterns across 14 different hives in a 342 subsequent year. In addition to foragers and winter bees, we also analyzed nurses, to help 343 understand whether microbiota differences between foragers and winter bees are linked 344 to seasonal changes or to behavioral or dietary differences. Moreover, we combined our 345 qPCR approach with 16S rRNA gene amplicon sequencing to expand our analysis to the 346 complete community of the honey bee gut microbiota.