Y.B. KORU, K.BEER, J.A.RODRIGUEZ-CORDERO, M.A. GIANNONI-GUZMAN., Y. ORTIZ-ALVARADO, M.A. DOKE, M. ANDERSON, C.L. ANDUJAR-SIERRA, E.C. COURTNEY, A. STRUBBE-NIEVES, E. AVILES-RIOS,, E. A. CITRON-RODRIGUEZ, A. MONTES-MERCADO, A.A. RUGGIERI, N. RODRIGUEZ, R. GIORDANO, R.K. DONTHU,, A.GHEZZI, T.GIRAY, J.L.AGOSTO-RIVERA

Introduction: Circadian rhythms are fundamental for honey bee colony survival and behaviors such as age-dependent division of labor. Nurse bees, which feed larvae and newly emerged bees, lack rhythmicity inside the colony. Forager bees, which go outside the colony to collect nectar, pollen, and water, have strong rhythmicity, which is utilized to predict foraging time. Previous studies show that gut microbes influence neurobiological processes such as behavioral development, learning, and memory in honey bees. However, the role of gut microbes in the development of circadian rhythm has not been elucidated. We hypothesize that gut microbes influence the ontogeny of circadian rhythm.

Methods: To test our hypothesis, we administered an antibiotic (tylosin) to the honey bees and measured their activity using locomotor activity monitors (LAMs). In addition, we conducted RNA-Seq assays on brain tissue of the bees that were exposed to antibiotic to understand its effect on neurotrophic factors. As a second manipulation, we caged newly emerged bees together with nurse bees to transfer the microbes of nurse bees to newly emerged bees and measured the locomotor activity of newly emerged bees. Lastly, we manually removed late-stage pupae from brood cells to minimize their gut bacterial load, allowed them to emerge as adults inside individual tubes placed on the LAMs, measured their activity, and compared their rhythmicity with naturally emerged bees.

Results: Our results showed that the bees that were in the antibiotic group developed less percent of rhythmicity compared to the bees in the control group. RNA-Seq data analysis found five differentially expressed genes; four of these genes are involved in brain development and function. Naturally emerged honey bees developed a greater percentage of rhythmic behavior compared to the pupae that emerged in the LAMs. On the contrary to other manipulations, interaction with nurse bees does not affect the onset of circadian rhythm.

Conclusion: Our results show that gut microbes are one of the important factors for the ontogeny of circadian rhythm.

Acknowledgements: NSF: 1736026, 1633184, NIH: 5P20GM103642, 2R25NS080687,