Seasonal trends in the midgut microbiota of honeybees
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- Master's theses (KBM) 
Honeybees are prominent crop pollinators and thus important for an effective food production. Without any apparent reason, massive bee colony losses appeared around the world, which started about a decade ago, and thereby the focus was set on bee health. The gut microbiota composition is crucial for health and immune system development both in mammals and insects, and factors shaping the gut microbiota has been intensely studied in humans and animals, three of which are frequently addressed are diet, hence exposure to the surrounding environment, host symbiosis and host genetics. The bee gut microbiota is bee specific and dominated by eight bacteria phylotyphes, which are found in almost all bees, and thus they are believed to be bee symbionts. This specific and simple microbiota in combination with the fact that bees are numerous, easy to monitor and the gut is easily accessible, the bee gut has been found to be a well suited model for gut microbiota studies. In this thesis the stability of the midgut microbiota of honeybees was addressed through sampling of bees throughout a season from May until October, where the impact of diet was the main focus. The data was analyzed using Sanger sequencing in combination with MCR-ASL computer analysis, which identified the dominating bacteria in the midgut and their relative ratio, hence bacteria composition. QPCR analysis was used to calculate the relative bacteria load in the data. The overall data showed that the midgut microbiota was not stable, and the dominating bacteria displayed apparent trends throughout the season. Analysis of distinct data sets including bees exposed to different diets, and with varying nutritional preferences, reviled bacteria in the midgut, which had nutritional preferences and exhibited possible niche adaptations. In addition results specified that the impact on the midgut microbiota by different diets was greater than the impact of same diet for a longer period of time. Biochemical profiling of the bee symbiont G.apicola, showed that this bacteria can utilize both glucose and fructose, something which has not been proven before using phenotypical tests. Competitive interactions between the two bee symbionts; G.apicola and S.alvi, was also detected.