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The decline in insect populations poses a growing threat to ecosystems and agriculture. Studies show an alarming loss of biomass among flying insects in Germany of up to 77 % over the last three decades [1]. Around 45 % of wild bee species found in Germany are considered to be at risk of extinction – with far-reaching consequences for fruit-growing regions such as Saxony and the Rhineland [2]. Agri-environmental measures are intended to counteract the increasing insect mortality caused, amongst other things, by the intensification of agriculture [1]. The extent to which certain pollinator groups, such as solitary wild bees – for example, mason bees (Osmia spp.) – benefit from these measures requires further analysis. Of great importance to bee health is their bacterial balance (microbiome). Whilst this has already been extensively researched in honeybees, it has not yet been sufficiently investigated in native wild bees [3]. Wild bees differ fundamentally from honey bees in their social behaviour, as they do not tend to their brood and the development of the bee larva depends entirely on the surrounding nesting material [4]. For example, the female red mason bee lays her eggs, together with pollen stores, in brood cells separated by clay walls (Figure 1).
However, in order to identify the wild bee microbiome, a reliable, standardisable method for isolating bacterial DNA from brood cell material is first required. Particular challenges arise from the adsorption of DNA onto particles, such as humic acids, as well as from the rapid degradation of DNA in the environmental samples by relevant enzymes [5]. To this end, various methods and approaches for DNA isolation are currently being tested, modified and compared with one another. The extracted DNA will then be used for the taxonomic identification of the microorganisms. To this end, the metabarcoding method is being employed. For this, specific DNA segments – referred to in scientific terminology as ‘barcodes’ – are first amplified using PCR and then sequenced (Figure 2).
For the specific identification of bacteria, the so-called 16S rRNA gene is used, which is frequently employed for the identification of bacteria [6]. This is then sequenced using the MinION from Oxford Nanopore Technologies and compared with known sequences from various bacterial strains (see Figure 2). The metabarcoding method offers the significant advantage that a comprehensive microbial spectrum can be captured from a relatively small amount of sample material [7]. The results can be used to draw conclusions about the bees’ health. This data is intended to evaluate the interplay between agricultural practices and agri-environmental measures in relation to various landscape scenarios and, where necessary, to adjust them.
About the person
Vanessa Bergler has been studying Biotechnology at Mittweida University of Applied Sciences since 2020. She is specialising in Genomic Biotechnology for her Master’s degree and, as part of her Master’s thesis, is supporting the project led by Lisa Prudnikow and Professor Wünschiers, focusing on the genetic detection of bacteria in environmental samples.
Bibliography
[1] Hallmann, CA., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H. (2017) More than 75 per cent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12 (10): e0185809. doi.org/10.1371/journal.pone.0185809
[2] Leopoldina – German National Academy of Sciences (ed.) 2020: Global Biodiversity in Crisis – What Can Germany and the EU Do About It? Proceedings of Discussion No. 24, Halle (Saale).
[3] Voulgari-Kokota, A., Steffan-Dewenter, I., Keller, A. (2020): Susceptibility of Red Mason Bee Larvae to Bacterial Threats Due to Microbiome Exchange with Imported Pollen Provisions, Insects 2020, 11, 373; doi:10.3390/insects11060373
[4] Voulgari-Kokota, A., McFrederick, Q., Steffan-Dewenter, I., Keller, A. (2019): Drivers, Diversity, and Functions of the Solitary-Bee Microbiota. Trends in Microbiology, December 2019, Vol. 27, No. 12 doi.org/10.1016/j.tim.2019.07.011
[5] Kelly, R., Shelton, O., Gallego, R., (2019): Understanding PCR Processes to Draw Meaningful Conclusions from Environmental DNA Studies, Scientific REPORTS (2019) 9:12133 doi.org/10.1038/s41598-019-48546-x
[6] Janda, M., Abbott, S. (2007): 16S rRNA Gene Sequencing for Bacterial Identification in the Diagnostic Laboratory: Pluses, Perils, and Pitfalls, JOURNAL OF CLINICAL MICROBIOLOGY, Sept. 2007, doi:10.1128/JCM.01228-07
[7] Ruppert, K., Kline, R., Rahman, S. (2019): Past, present, and future perspectives of environmental DNA (eDNA) metabarcoding: A systematic review of methods, monitoring and applications of global eDNA, Global Ecology and Conservation 17 (2019) e00547, doi.org/10.1016/j.gecco.2019.e00547
