Abstract
Microbial activity is known to have profound impact on bee ecology and physiology, both by beneficial and pathogenic effects. Most information about such associations is available for colony-building organisms, and especially the honey bee. There, active manipulations through worker bees result in a restricted diversity of microbes present within the colony environment. Microbial diversity in solitary bee nests remains unstudied, although their larvae face a very different situation compared with social bees by growing up in isolated compartments. Here, we assessed the microbiota present in nests and pre-adults of Osmia bicornis, the red mason bee, by culture-independent pyrosequencing. We found high bacterial diversity not comparable with honey bee colonies. We identified a variety of bacteria potentially with positive or negative interactions for bee larvae. However, most of the other diverse bacteria present in the nests seem to originate from environmental sources through incorporated nest building material and stored pollen. This diversity of microorganisms may cause severe larval mortality and require specific physiological or symbiotic adaptations against microbial threats. They may however also profit from such a diverse environment through gain of mutualistic partners. We conclude that further studies of microbiota interaction in solitary bees will improve the understanding of fitness components and populations dynamics.
Highlights
Beekeepers early identified the impact of bacterial organisms on honey bees, making pathological analyses and serological cultures important tools to assess hive diseases and oncoming threats [1]
Honey-bees are very susceptible to some bacteria, as exemplified by the American and European foulbrood caused by Paenibacillus larvae subsp. larvae and Melissococcus plutonius, respectively
Sequencing results Two nest chambers including bees of an artificial reed stack containing Osmia bicornis were investigated through pyrosequencing for their bacterial communities
Summary
Beekeepers early identified the impact of bacterial organisms on honey bees, making pathological analyses and serological cultures important tools to assess hive diseases and oncoming threats [1]. The organism of interest in this study, Osmia bicornis (Megachilidae), is a species of solitary bees native to Europe and Northern Africa. It inhabits natural as well as anthropogenically altered environments. Each brood cell with stored pollen and an individual egg is separated with a loam wall and the nest entrance is closed with loam This results in several chambers following each other so that each harbors only a single egg. Hatching occurs after approximately a week, and development of the larvae takes place until late summer. Osmia bicornis is a widespread and well investigated solitary bee species that shows high levels of unexplained larval mortality [16], for bacteria neither pathogens nor mutualistic symbionts have been identified so far [17]
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