Effects of pollen supply on Apis mellifera worker longevity and body weight in the presence and absence of an intact gut microbiota

Gut microbiota are known to foster pollen digestion in honey bee workers,
Apis mellifera, thereby enhancing longevity and body weight gain. However,
it is currently not known how longevity and body weight gain are effected
when gut microbiota are reduced in bees with or without access to pollen.
Here, using a hoarding cage set-up with freshly emerged summer workers, we
manipulated the gut microbiota of half the bees with the antibiotic
tetracycline (ABX), and left the other half untreated on a sucrose
solution diet. Afterwards, all bees were assigned to either sucrose diets
or sucrose plus ad libitum access to pollen (N=4 treatments, N=26
bees/treatment, N=10 replicates/treatment, N=1040 total workers). The data
confirm that pollen has a positive effect on longevity and body weight in
workers with an unmanipulated gut microbiota. Surprisingly, the
antibiotics alone also improved the longevity and body weight of the
workers fed a strictly sucrose diet, potentially explained by the
reduction of harmful bacteria. However, this positive effect was always
reversed in the presence of pollen, underscoring the innate value of
natural microbiota on pollen digestion. In conclusion, a combination of
adequate pollen supply and an intact gut microbiota appears crucial to
honey bee worker health, calling for respective efforts to ensure both in
managed colonies.