Honeybee symbionts, predominantly bacteria, play important roles in honeybee health, nutrition, and pathogen protection, thereby supporting colony health. On the other hand, fungi are often considered indicators of poor bee health, and honeybee microbiome studies generally exclude fungi and yeasts. We hypothesized that yeasts may be an important aspect of early honeybee biology, and if yeasts provide a mutual benefit to their hosts, then honeybees could provide a refuge during metamorphosis to ensure the presence of yeasts at emergence. We surveyed for yeast and fungi during pupal development and metamorphosis in worker bees using fungal‐specific quantitative polymerase chain reaction (qPCR), next‐generation sequencing, and standard microbiological culturing. On the basis of yeast presence in three distinct apiaries and multiple developmental stages, we conclude that yeasts can survive through metamorphosis and in naïve worker bees, albeit at relatively low levels. In comparison, known bacterial mutualists, like Gilliamella and Snodgrassella, were generally not found in pre‐eclosed adult bees. Whether yeasts are actively retained as an important part of the bee microbiota or are passively propagating in the colony remains unknown. Our demonstration of the constancy of yeasts throughout development provides a framework to further understand the honeybee microbiota.

Taking into account that fructophilic lactic acid bacteria (FLAB) can play an important role in the health of honey bees and can be used as probiotics, phenotypic properties of probiotic interest of Lactobacillus kunkeei (12 strains) and Fructobacillus fructossus bacteria (2 strains), isolated from Apis mellifera gastrointestinal tract, have been studied. We have evaluated survival of tested FLAB in honey bee gut, their susceptibility to antibiotics (ampicillin, erythromycin, tylosin), cell surface hydrophobicity, auto-aggregation ability, co-aggregation with model pathogenic bacteria, biofilm formation capacity, and effect of studied FLAB, added to sucrose syrup bee diet, on longevity of honey bees. The tested FLAB exhibited good gastrointestinal tract tolerance and high antibiotic susceptibility, which are important criteria in the screening of probiotic candidates. It was also found that all FLAB studied have high cell surface hydrophobicity and fulfil next selection criterion for their use as probiotics. Symbionts of A. mellifera showed also auto- and co-aggregation capacities regarded as valuable features for biofilm formation and inhibition of pathogens adhesion to the bee gut cells. Biofilm-development ability is a desired characteristic of probiotic lactic acid bacteria. As indicated by quantitative crystal violet-stained microplate assay and confocal laser scanning microscopy imaging, all studied A. mellifera gut isolates exhibit a biofilm positive phenotype. Moreover, it was also documented, on honey bees kept in cages, that supplementation of A. mellifera sucrose diet with FLAB decreases mortality and improves significantly longevity of honey bees. Presented research showed that A. mellifera FLAB symbionts are good candidates for application as probiotics.

Recent years have witnessed a fall in the numbers of bee colonies worldwide. To a large extent, this is due to diseases affecting honeybees. One such disease is nosemosis, which is caused by fungi from the genus Nosema. The antibiotic fumagallin used to be administered to treat nosemosis, but as it was found capable of being transferred to bee products, this practice has ceased. We therefore focused on natural substances for treating this disease, among them, aqueous extracts of the nest carton produced by the jet-black ant (Lasius fuliginosus). We tested the influence of 0.1% and 1% concentrations of such extracts on the incidence of nosemosis in honeybees. The "birch carton 2" extract turned out to be the most effective inhibitor of this disease. The incidence of nosemosis following the administration of this extract, as manifested by the number of spores, fell ca 18-fold in comparison with the control. Moreover, the "birch carton 2" extract was not found to be toxic towards bees.

Nowadays, there is an urgent need to look for antimicrobial substances due to a widespread occurrence of multidrug resistant bacterial and fungal strains. Honey with its antimicrobial properties is a very promising substance with many valuable properties. In this study we examined for the first time antimicrobial properties of novel varietal honeys. The experiments were carried out with 11 honey samples, i.e.: Plum, Rapeseed, Lime, Phacelia, Honeydew, Sunflower, Willow, and Multifloral-P (Prunus spinosa L.), Multifloral-AP (Acer negundo L., Prunus spinosa L.), Multifloral-Sa (Salix sp.), Multifloral-Br (Brassica napus L.). Their antimicrobial activity was tested against bacteria (such as Escherichia coli, Bacillus circulans, Staphylococcus aureus, Pseudomonas aeruginosa), yeasts (such as Saccharomyces cerevisiae and Candida albicans) and mold fungi (such as Aspergillus niger). In tested honeys, phenolic acids were one of the most important group of compounds with antimicrobial activity. In our study, the highest amount of phenolic acids was found in honeydew honey (808.05 µg GAE/g) with the highest antifungal activity aiming A. niger. Among the tested phenolic acids, caffeic acid was in the greatest amount, which was found in the highest amounts in honeys as: phacelia − 356.72 µg/g, multifloral (MSa) and multifloral (MBr) − 318.9 µg/g. The highest bactericidal activity against S. aures was found in multifloral honeys MSa and MBr. Additionally, the highest amounts of syringic acid and cinnamic acid were identified in rapeseed honey. Multifloral honey (MAP) showed the highest bactericidal activity against E. coli, and multifloral honey (MSa) against S. aureus. Additionally, multifloral honey (MBr) was effective against both bacteria: E. coli and S. aureus. Novel varietal honeys tested in our study show various levels of antibacterial and antifungal activity and alhough they had some limitations, they can still enhance drug treatment against multidrug resistant bacterial and fungal strains.

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