Chemie | Biochemie | Medizin


Vanessa Küng, 2000 | Reinach, BL


The microbiome of honey bees (Apis mellifera) is known for regulating host health. Research shows how Lactobacillus kunkeei, being part of the core honey bee microbiome, stimulate host immunity. Yet, the environmental influences on these microbes are unclear. In this study, the abundance of L. kunkeei in 12 organic, 12 conventional rural and 12 urban honey samples from the Basel area were compared. Quantitative polymerase chain reaction (qPCR) and de Man-Rogosa-Sharpe agar plating was performed and collated with site studies conducted within 1 km around each beehive. While previous studies have shown that pesticides decrease L. kunkeei abundance in rural areas, the results of this study, obtained by the qPCR approach, showed a significantly lower L. kunkeei abundance in urban samples, having a median of 275,798 bacterial cells per ml honey, than in organic ones, having a median of 5,028,263 bacterial cells per ml honey. The conventional rural samples had a median of 1,665,780 bacterial cells per ml honey. This work showed how abundances may vary between different apiaries in Switzerland, but no driving causes could be identified. To prevent a negative impact on host health, future studies on the environmental influences on the honey bee microbiome are needed.


In an experiment consisting of 36 samples, I tested the hypotheses (i) that L. kunkeei abundance varies depending on beehive location and (ii) that the variation correlates with the above-mentioned groups, with the smallest L. kunkeei abundance expected in the conventional rural and organic samples.


The honey samples were obtained from 12 urban, 12 conventional rural and 12 organic bee colonies. Abundances of L. kunkeei were assessed by plating the samples on de Man-Rogosa-Sharpe agar plates at the University of Basel. Secondly, it was assessed by extracting the DNA from the honey using the ZymoBIOMICS DNA Microprep Kit (Zymo Research) and then doing a quantitative polymerase chain reaction (qPCR) using specific L. kunkeei primers and universal primers targeting all bacteria in a StepOnePlus instrument (Applied Biosystems) at the University of Lausanne. Additionally, a site study of the one kilometer surrounding each hive was conducted using the Geodatenportal. The QuantStudio Design & Analysis Software was used to calculate L. kunkeei abundances from the qPCR approach with the help of a standard curve performed by Kesnerova et al. (2017).


Concerning the agar plating, colonies were detected on 19 honey samples (7 organic/8 conventional rural/4 urban), whereas in the remaining 17 honeys, no colonies were observed. The qPCR results showed that the highest group median of 5,028,263 bacterial cells per ml honey was in the organic group, followed by the conventional rural group with a median of 1,665,780 bacterial cells per ml honey. The urban group had the lowest median of 275,798 bacterial cells per ml honey. Moreover, the difference in L. kunkeei abundance present in the organic group was significantly higher than in the urban group. There was no significant difference within any of the other groups. Concerning the site study, the highest potential pesticide exposure was found in the conventional rural group with 23% of the total area, which was around double of what was found in the other two groups. The potential pollution exposure was around 6.5 times higher in the urban group than in both of the rural groups.


This work showed how the microbiome of honey bees may vary between different apiaries in Switzerland. Therefore, the first hypothesis (i) was confirmed, since the abundance of L. kunkeei as a core bacterial species of the bee microbiome, and consequently in the honey, did vary between honeys from different beehive locations. But the second hypothesis (ii) was contradicted, as no correlation between any environmental factors and L. kunkeei abundance could be identified. One would also have to investigate if L. kunkeei abundance is reduced in the honey bee gastrointestinal tract. This study emphasizes the need for future studies on the environmental influence on the honey bee microbiome to prevent negative consequences for host health.


There seem to be environmental parameters responsible for a lower L. kunkeei abundance in honey of urban regions; however, no single cause could be identified. But it is feasible that multiple factors acting together may influence the abundance of L. kunkeei. Therefore, the data in this study is suitable for future studies that aim to understand the key driving factors causing the observed differences in L. kunkeei abundance.



Würdigung durch den Experten

Prof. Dr. Leo Meile

Die vorzüglich abgefasste Arbeit (in Englisch) beschreibt ein Projekt, das dank beeindruckend-komplexer Zusammenarbeit mit zwei Universitäts-Laboratorien und 18 Bienenhaltern entstand. Honiganalysen von Vanessa Küng aus 36 Bienenvölkern zeigten, dass Umweltfaktoren und Imker-Betriebsweise das Bakterium Lactobacillus kunkei, ein Indikator für ein intaktes Mikrobiom der Honigbiene, modulierten. Die Arbeit überzeugt in der Methodik, durchsichtiger Struktur, Daten-Generierung, sowie vorsichtigen Interpretationen. Dies zeigt ein bereits gut entwickeltes wissenschaftliches Flair der Jungforscherin.



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Gymnasium Münchenstein, Münchenstein
Lehrerin: Dr. Claudia Zwahlen