The Western honey bee (Apis mellifera) is a vital agricultural pollinator whose populations are threatened by the parasitic mite Varroa destructor and associated pathogens. While the impact of Paenibacillus species on honey bees, particularly Paenibacillus larvae causing American foulbrood, is documented, their effect on the microbiota of Varroa mites remains unclear. This study aimed to investigate the influence of Paenibacillus sp. on the bacterial communities of Varroa mites and adult honey bees. We hypothesized that Paenibacillus sp. would significantly alter the microbiota of Varroa mites but have minimal effect on that of adult honey bees. Utilizing 16S rRNA sequencing data from a previous study, we reanalyzed samples categorized into four groups based on Paenibacillus sp. infection load: highly infected and lowly infected honey bees (A. mellifera) and mites (V. destructor). Infection status was determined by Paenibacillus sp. read counts, with more than three reads indicating high infection. Microbial diversity was assessed using alpha and beta diversity metrics. Co-occurrence networks were constructed to visualize bacterial community assemblies, and network robustness was evaluated through node addition and removal tests. Keystone taxa were identified based on eigenvector centrality and relative abundance. Highly infected Varroa mites exhibited a significant reduction in alpha diversity and a markedly different bacterial community composition compared to lowly infected mites (p < 0.05). Their bacterial co-occurrence networks showed decreased connectivity and robustness, indicating a disruptive effect of Paenibacillus sp. In contrast, adult honey bees displayed no significant differences in alpha diversity or network structure between highly and lowly infected groups (p > 0.05), suggesting a resilient microbiota. Keystone taxa analysis revealed fewer central species in highly infected Varroa mites, potentially impacting network stability. High Paenibacillus sp. infection is associated with significant alterations in the microbiota of Varroa mites, disrupting bacterial communities and potentially affecting mite physiology. The microbiota of adult honey bees appears more robust against Paenibacillus sp. influence. These findings enhance our understanding of the complex interactions within the "honey bee-mite-microorganism" system and may inform future strategies for managing Varroa mite infestations and associated pathogens.

• Klíčová slova
• Apis mellifera, Microbial networks, Microbiota analysis, Paenibacillus sp., Varroa destructor,
• Publikační typ
• časopisecké články MeSH

The honey bee, Apis mellifera, is a globally important species that suffers from a variety of pathogens and parasites. These parasites and pathogens may have sublethal effects on their bee hosts via an array of mechanisms, including through a change in symbiotic bacterial taxa. Our aim was to assess the influence of four globally widespread parasites and pathogens on the honey bee bacteriome. We examined the effects of the ectoparasitic mite Varroa destructor, the fungal pathogens Nosema apis and Nosema ceranae, and the trypanosome Lotmaria passim. Varroa was detected by acaricidal treatment, Nosema and L. passim by PCR, and the bacteriome using MiSeq 16S rRNA gene sequencing. Overall, the 1,858,850 obtained sequences formed 86 operational taxonomic units (OTUs) at 3 % dissimilarity. Location, time of year, and degree of infestation by Varroa had significant effects on the composition of the bacteriome of honey bee workers. Based on statistical correlations, we found varroosis more important factor than N. ceranae, N. apis, and L. passim infestation influencing the honey bee bacteriome and contributing to the changes in the composition of the bacterial community in adult bees. At the population level, Varroa appeared to modify 20 OTUs. In the colonies with high Varroa infestation levels (varroosis), the relative abundance of the bacteria Bartonella apis and Lactobacillus apis decreased. In contrast, an increase in relative abundance was observed for several taxa including Lactobacillus helsingborgensis, Lactobacillus mellis, Commensalibacter intestini, and Snodgrassella alvi. The results showed that the "normal" bacterial community is altered by eukaryotic parasites as well as displaying temporal changes and changes associated with the geographical origin of the beehive.

• Klíčová slova
• Bacteria, Lotmaria passim, Nosema apis, Nosema ceranae, Sequencing, Varroa destructor,
• MeSH
• Bartonella klasifikace   genetika   izolace a purifikace   MeSH
• infestace roztoči patologie   MeSH
• Kinetoplastida patogenita   MeSH
• Lactobacillus klasifikace   genetika   izolace a purifikace   MeSH
• mikrobiota genetika   MeSH
• Nosema patogenita   MeSH
• RNA ribozomální 16S genetika   MeSH
• symbióza MeSH
• Varroidae patogenita   MeSH
• včely mikrobiologie   parazitologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• RNA ribozomální 16S MeSH

The ectoparasitic mite Varroa destructor is a major pest of the honeybee Apis mellifera. In a previous study, bacteria were found in the guts of mites collected from winter beehive debris and were identified using Sanger sequencing of their 16S rRNA genes. In this study, community comparison and diversity analyses were performed to examine the microbiota of honeybees and mites at the population level. The microbiota of the mites and honeybees in 26 colonies in seven apiaries in Czechia was studied. Between 10 and 50 Varroa females were collected from the bottom board, and 10 worker bees were removed from the peripheral comb of the same beehive. Both bees and mites were surface sterilized. Analysis of the 16S rRNA gene libraries revealed significant differences in the Varroa and honeybee microbiota. The Varroa microbiota was less diverse than was the honeybee microbiota, and the relative abundances of bacterial taxa in the mite and bee microbiota differed. The Varroa mites, but not the honeybees, were found to be inhabited by Diplorickettsia. The relative abundance of Arsenophonus, Morganella, Spiroplasma, Enterococcus, and Pseudomonas was higher in Varroa than in honeybees, and the Diplorickettsia symbiont detected in this study is specific to Varroa mites. The results demonstrated that there are shared bacteria between Varroa and honeybee populations but that these bacteria occur in different relative proportions in the honeybee and mite bacteriomes. These results support the suggestion of bacterial transfer via mites, although only some of the transferred bacteria may be harmful.

• Klíčová slova
• Apis mellifera, Arsenophonus, Diplorickettsia, Spiroplasma, Symbiosis, Varroa destructor,
• MeSH
• biodiverzita MeSH
• DNA bakterií genetika   MeSH
• mikrobiota * MeSH
• RNA ribozomální 16S genetika   MeSH
• roční období MeSH
• sekvenční analýza DNA MeSH
• Spiroplasma klasifikace   izolace a purifikace   MeSH
• symbióza MeSH
• Varroidae mikrobiologie   MeSH
• včely mikrobiologie   parazitologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• DNA bakterií MeSH
• RNA ribozomální 16S MeSH