Research Group:	Institute for Bee Research, Dept. for Molecular Microbiology and Bee Diseases
Address:	Friedrich-Engels-Str. 32, 16540 Hohen Neuendorf / Berlin
Supervisor:	PD Dr. Elke Genersch

Project Description

Microsporidia are fungal-related, obligate intracellular parasites infecting vertebrates and invertebrates. Three microsporidian species are known to infect bees. Managed Western honey bees (Apis mellifera) and wild bumblebees (Bombus sp.) are frequently found infected by Nosema apis and N. bombi, respectively. N. ceranae has been considered to be specific for the Eastern honey bee (A. cerana) but switched host from A. cerana to A. mellifera approximately 20 years ago¹ and from A. mellifera to Bombus terrestris quite recently². N. ceranae is now considered an emerging and deadly parasite of A. mellifera and Bombus sp.³. The impact of the emerging parasite N. ceranae on honey bees and bumblebees is poorly understood and molecular details of pathogen-host interaction remain elusive.

We recently established reliable molecular tools for the differentiation of Nosema^1,4. These tools enabled us to perform long-term epidemiological studies on the prevalence and consequences of Nosema infections in honey bees^1,5,6. As a prerequisite to analyzing pathogen-host interactions during Nosema infection in bees, we recently established in vitro infections of primary honey bee gut cells with Nosema and developed a cell culture model using a lepidopteran cell line⁷. Employing this in vitro infection model we were able (i) to elucidate the entire intracellular life cycle of these pathogens⁷ and (ii) to develop a medium throughput screening assay for the identification of anti-nosemosis drugs.

In our project we will concentrate on the emerging deadly bee parasite N. ceranae in honey bees and bumblebees. It has been shown that the outcome of N. ceranae infection in honey bees varies considerably. We hypothesize that these differences are due to differentially virulent or host-adapted strains of N. ceranae. To address this question, we will sample bumblebees and honey bees and analyze the N. ceranae infection status, thus collecting epidemiological data on N. ceranae infections in these hosts. We will establish a multi locus sequence typing (MLST) scheme for N. ceranae and provide population genetic evidence for the presence or absence of distinct N. ceranae strains. Furthermore, we will assess the virulence of these strains in honey bees and bumblebees via experimental infections to identify virulence differences between N. ceranae strains or susceptibility differences between host genotypes. Future work will be dedicated to screen our cell culture model and also experimentally infected bees for immune-related transcript changes using an established quantitative-PCR array⁸, RT-qPCR, and RNA-seq.

References: (1) Klee J, Besana AM, Genersch E et al., J Invertebr Pathol 96:1-10; (2) Graystock P, Yates K, Darvill B et al., 2013, J Invertebr Pathol 114:114-119; (3) Fürst MA, McMahon DP, Osborne JL, et al. 2014, Nature 506:364-366; (4) Gisder S, Genersch E, 2013, J Invertebr Pathol 113:1-6; (5) Gisder S, Hedtke K, Möckel N, Frielitz MC, Linde A, Genersch E, 2010, Appl Environ Microbiol 76:3032-3038; (6) Genersch E, von der Ohe W, Kaatz H et al., 2010, Apidologie 41:332-352; (7) Gisder S, Möckel N, Linde A, Genersch E, 2011, Environ Microbiol 13:404-413; (8) Evans JD, 2006 J Invertebr Pathol 93:135-139.