Prevalence of pathogens and other associated microorganisms in Turkish honeybee subspecies and differential responses to nosema ceranae infection

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2015
Tozkar, Cansu Özge
Honey bees face numerous biotic threats from viruses to bacteria, fungi, protists, and mites. Here we describe a thorough analysis of microbes harbored by worker honey bees collected from field colonies in geographically distinct regions of Turkey. Turkey is one of the World’s most important centers of apiculture, harboring 5 subspecies of Apis mellifera L., approximately 20% of the honey bee subspecies in the world. We use deep ILLUMINA-based RNA sequencing to capture RNA species for the honey bee and a sampling of all non-endogenous species carried by bees. After trimming and mapping these reads to the honey bee genome, approximately 10% of the sequences (9-10 million reads per library) remained. These were then mapped to a curated set of public sequences containing ca. 60 megabase-pairs of sequence representing known microbial species associated with honey bees. Levels of key honey bee pathogens were confirmed using quantitative PCR screens. We contrast microbial matches across different sites in Turkey, showing new country recordings of Lake Sinai virus, two Spiroplasma bacterium species, symbionts Candidatus Schmidhempelia bombi, Frischella perrara, Snodgrassella alvi, Gilliamella apicola, Lactobacillus spp.), neogregarines, and a trypanosome species. By using metagenomic analysis, this study also reveals deep molecular evidence for the presence of bacterial pathogens (Melissococcus plutonius, Paenibacillus larvae), Varroa destructor-1 virus, Sacbrood virus, Apis filamentous virus and fungi. Despite this effort we did not detect KBV, SBPV, Tobacco ringspot virus, VdMLV (Varroa Macula like virus), Acarapis spp., Tropilaeleps spp. and Apocephalus (phorid fly). We discuss possible impacts of management practices and honey bee subspecies on microbial retinues. The described workflow and curated microbial database will be generally useful for microbial surveys of healthy and declining honey bees. Additionally we addressed the immune defence reactions, locomotor activity differences of five honey bee subspecies upon N. ceranae infection and confirmed the phylogenetic relationship between these subspecies. It was observed that honey bee immune system quickly activated defence mechanisms for all of five the subspecies after infection with N .ceranae, which includes the increase in the expression of genes encoding antimicrobial peptides.
Citation Formats
C. Ö. Tozkar, “Prevalence of pathogens and other associated microorganisms in Turkish honeybee subspecies and differential responses to nosema ceranae infection,” Ph.D. - Doctoral Program, Middle East Technical University, 2015.