ber Isolierung, Kultur und Taxonomie einiger Anobiidensymbionten (Insecta, Coleoptera)

Rediscovering a Forgotten System of Symbiosis: Historical Perspective and Future Potential

While the majority of symbiosis research is focused on bacteria, microbial eukaryotes play important roles in the microbiota and as pathogens, especially the incredibly diverse Fungi kingdom. The recent emergence of widespread pathogens in wildlife (bats, amphibians, snakes) and multidrug-resistant opportunists in human populations (Candida auris) has highlighted the importance of better understanding animal-fungus interactions. Regardless of their prominence there are few animal-fungus symbiosis models, but modern technological advances are allowing researchers to utilize novel organisms and systems. Here, I review a forgotten system of animal-fungus interactions: the beetle-fungus symbioses of Drugstore and Cigarette beetles with their symbiont Symbiotaphrina. As pioneering systems for the study of mutualistic symbioses, they were heavily researched between 1920 and 1970, but have received only sporadic attention in the past 40 years. Several features make them unique research organisms, including (1) the symbiont is both extracellular and intracellular during the life cycle of the host, and (2) both beetle and fungus can be cultured in isolation. Specifically, fungal symbionts intracellularly infect cells in the larval and adult beetle gut, while accessory glands in adult females harbor extracellular fungi. In this way, research on the microbiota, pathogenesis/infection, and mutualism can be performed. Furthermore, these beetles are economically important stored-product pests found worldwide. In addition to providing a historical perspective of the research undertaken and an overview of beetle biology and their symbiosis with Symbiotaphrina, I performed two analyses on publicly available genomic data. First, in a preliminary comparative genomic analysis of the fungal symbionts, I found striking differences in the pathways for the biosynthesis of two B vitamins important for the host beetle, thiamine and biotin. Second, I estimated the most recent common ancestor for Drugstore and Cigarette beetles at 8.8-13.5 Mya using sequence divergence (CO1 gene). Together, these analyses demonstrate that modern methods and data (genomics, transcriptomes, etc.) have great potential to transform these beetle-fungus systems into model systems again.

Nine new Candida species near C. membranifaciens isolated from insects

14 different yeasts were isolated from the gut of a variety of insects, including beetles, lacewings, fishflies, craneflies, and a cockroach. One of the yeasts was found both in the gut and on the body surface of a beetle larva. Based on ribosomal DNA sequence comparisons and phenotypic characters, the yeasts were identified as Candida membranifaciens, C. tenuis, Pichia nakazawae, and nine undescribed taxa in Saccharomycotina. All the undescribed taxa reproduced only asexually, and they fit within the limits of the polyphyletic genus Candida. The new species and their type strains are Candida blattariae NRRL Y-27703T, C. amphixiae NRRL Y-27704T, C. michaelii NRRL Y-27705T, C. cerambycidarum NRRL Y-27706T, C. gorgasii NRRL Y-27707T, C. endomychidarum NRRL Y-27708T, C. temnochilae NRRL Y-27763T, C. sinolaborantium NRRL Y-27765T, and C. lessepsii NRRL Y-27766T spp. nov. Phylogenetic analysis of combined small and large subunit ribosomal DNA sequences placed C. amphixiae, C. michaelii, C. cerambycidarum, C. gorgasii, C. endomychidarum, and C. lessepsii in a statistically well supported clade with C. blattariae, C. membranifaciens, C. friedrichii, and C. buinensis as sisters to the clade. The other two new taxa, C. temnochilae and C. sinolaborantium, formed an independent clade basal to the major clade containing C. membranifaciens and closely related taxa. C. sinolaborantium occurred in both Panama and the USA, but there were genetic differences between the isolates from the two places.