The trisaccharide melezitose impacts honey bees and their intestinal microbiota

Kiwi (Actinidia deliciosa) juice as a natural inhibitor of the enzymatic activity of sugarcane juice, insights from experimental assessment and molecular docking analysis

The present work evaluated kiwi juice addition alongside pasteurization (at 85 °C for 5 min) or microwave treatment (for 3 min) on the quality improvement of sugarcane juice. The juice was treated in the presence of kiwi juice (0-8%), and its physicochemical properties and microbial load were compared with raw juice. The study also highlighted the key enzymes causing sugarcane juice discoloration, peroxidase (POD) and polyphenol oxidase (PPO), by quantifying kiwi juice constituents using GC-MS and monitoring their effects by molecular docking. Kiwi addition considerably raised (p < 0.05) acidity, ascorbic acid (54.28%), and phenolic compounds (32%), and decreased the POD and PPO activity of raw cane juice. Pasteurization in the presence of kiwi, rather than microwave treatment, has significantly (p < 0.05) increased the phenolic compounds and reduced POD and PPO activities until barley was detected. Molecular docking revealed that heptacosane, oleic acid, and melezitose are the primary kiwi components responsible for enzyme inactivation.

In vitro Antibacterial Activity and Secondary Metabolite Profiling of Endolichenic Fungi Isolated from Genus Parmotrema

The endolichenic fungi are an unexplored group of organisms for the production of bioactive secondary metabolites. The aim of the present study is to determine the antibacterial potential of endolichenic fungi isolated from genus Parmotrema. The study is continuation of our previous work, wherein a total of 73 endolichenic fungi were isolated from the lichenized fungi, which resulted in 47 species under 23 genera. All the isolated endolichenic fungi were screened for preliminary antibacterial activity. Five endolichenic fungi-Daldinia eschscholtzii, Nemania diffusa, Preussia sp., Trichoderma sp. and Xylaria feejeensis, were selected for further antibacterial activity by disc diffusion method. The zone of inhibition ranged from 14.3 ± 0.1 to 23.2 ± 0.1. The chemical composition of the selected endolichenic fungi was analysed through GC-MS, which yielded a total of 108 compounds from all the selected five endolichenic fungi. Diethyl phthalate, 1-hexadecanol, dibutyl phthalate, n-tetracosanol-1, 1-nonadecene, pyrrol[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methyl) and tetratetracontane were found to be common compounds among one or the other endolichenic fungi, which possibly were responsible for antibacterial activity. GC-MS data were further analysed through Principal Component Analysis which showed D. eschscholtzii to be with unique pattern of expression of metabolites. Compound confirmation test revealed coumaric acid to be responsible for antibacterial activity in D. eschscholtzii. So, the study proves that endolichenic fungi that inhabit lichenized fungal thalli could be a source of potential antibacterial compounds.

To each their own! Nectar plasticity within a flower mediates distinct ecological interactions

Nuptial and extranuptial nectaries are involved in interactions with different animal functional groups. Nectar traits involved in pollination mutualisms are well known. However, we know little about those traits involved in other mutualisms, such as ant-plant interactions, especially when both types of nectaries are in the same plant organ, the flower. Here we investigated if when two types of nectaries are exploited by distinct functional groups of floral visitors, even being within the same plant organ, the nectar secreted presents distinct features that fit animal requirements. We compared nectar secretion dynamics, floral visitors and nectar chemical composition of both nuptial and extranuptial nectaries in natural populations of the liana Amphilophium mansoanum (Bignoniaceae). For that we characterized nectar sugar, amino acid and specialized metabolite composition by high-performance liquid chromatography. Nuptial nectaries were visited by three medium- and large-sized bee species and extranuptial nectaries were visited mainly by ants, but also by cockroaches, wasps and flies. Nuptial and extranuptial nectar differed regarding volume, concentration, milligrams of sugars per flower and secretion dynamics. Nuptial nectar was sucrose-dominated, with high amounts of γ-aminobutyric acid and β-aminobutyric acid and with theophylline-like alkaloid, which were all exclusive of nuptial nectar. Whereas extranuptial nectar was hexose-rich, had a richer and less variable amino acid chemical profile, with high amounts of serine and alanine amino acids and with higher amounts of the specialized metabolite tyramine. The nectar traits from nuptial and extranuptial nectaries differ in energy amount and nutritional value, as well as in neuroactive specialized metabolites. These differences seem to match floral visitors' requirements, since they exclusively consume one of the two nectar types and may be exerting selective pressures on the composition of the respective resources of interest.

Sugar perception in honeybees

Honeybees (Apis mellifera) need their fine sense of taste to evaluate nectar and pollen sources. Gustatory receptors (Grs) translate taste signals into electrical responses. In vivo experiments have demonstrated collective responses of the whole Gr-set. We here disentangle the contributions of all three honeybee sugar receptors (AmGr1-3), combining CRISPR/Cas9 mediated genetic knock-out, electrophysiology and behaviour. We show an expanded sugar spectrum of the AmGr1 receptor. Mutants lacking AmGr1 have a reduced response to sucrose and glucose but not to fructose. AmGr2 solely acts as co-receptor of AmGr1 but not of AmGr3, as we show by electrophysiology and using bimolecular fluorescence complementation. Our results show for the first time that AmGr2 is indeed a functional receptor on its own. Intriguingly, AmGr2 mutants still display a wildtype-like sugar taste. AmGr3 is a specific fructose receptor and is not modulated by a co-receptor. Eliminating AmGr3 while preserving AmGr1 and AmGr2 abolishes the perception of fructose but not of sucrose. Our comprehensive study on the functions of AmGr1, AmGr2 and AmGr3 in honeybees is the first to combine investigations on sugar perception at the receptor level and simultaneously in vivo. We show that honeybees rely on two gustatory receptors to sense all relevant sugars.

Comparative Genomics of Acetic Acid Bacteria within the Genus Bombella in Light of Beehive Habitat Adaptation

It is known that the bacterial microbiota in beehives is essential for keeping bees healthy. Acetic acid bacteria of the genus Bombella colonize several niches in beehives and are associated with larvae protection against microbial pathogens. We have analyzed the genomes of 22 Bombella strains of different species isolated in eight different countries for taxonomic affiliation, central metabolism, prophages, bacteriocins and tetracycline resistance to further elucidate the symbiotic lifestyle and to identify typical traits of acetic acid bacteria. The genomes can be assigned to four different species. Three genomes show ANIb values and DDH values below species demarcation values to any validly described species, which identifies them as two potentially new species. All Bombella spp. lack genes in the Embden–Meyerhof–Parnas pathway and the tricarboxylic acid cycle, indicating a focus of intracellular carbohydrate metabolism on the pentose phosphate pathway or the Entner–Doudoroff pathway for which all genes were identified within the genomes. Five membrane-bound dehydrogenases were identified that catalyze oxidative fermentation reactions in the periplasm, yielding oxidative energy. Several complete prophages, but no bacteriocins, were identified. Resistance to tetracycline, used to prevent bacterial infections in beehives, was only found in Bombella apis MRM1T. Bombella strains exhibit increased osmotolerance in high glucose concentrations compared to Gluconobacter oxydans, indicating adaption to high sugar environments such as beehives.

Antimicrobial Activity from Putative Probiotic Lactic Acid Bacteria for the Biological Control of American and European Foulbrood Diseases

The balance of the gut microbiome is important for the honey bee’s growth and development, immune function and defense against pathogens. The use of a beneficial bacteria-based strategy for the prevention and biocontrol of American foulbrood (AFB) and European foulbrood (EFB) diseases in honey bees offers interesting prospects. Lactic acid bacteria (LAB) are common inhabitants of the gastrointestinal tract of the honey bee. Among LABs associated with bee gut microbiota, Lactiplantibacillus plantarum (previously Lactobacillus plantarum) and Apilactobacillus kunkeei (formerly classified as Lactobacillus kunkeei) are two of the most abundant species. In this study, four Lactiplantibacillus plantarum strains and four Apilactobacillus kunkeei strains, isolated from the gastrointestinal tract of honey bee (Apis mellifera L.) were selected for their in vitro inhibition ability of Paenibacillus larvae ATCC 9545 and Melissococccus plutonius ATCC 35311. In addition, these LABs have been characterized through some biochemical and functional characteristics: cell surface properties (hydrophobicity and auto-aggregation), carbohydrates assimilation and enzymatic activities. The antimicrobial, biochemical and cell surface properties of these LABs have been functional to their candidature as potential probiotics in beekeeping and for the biocontrol of AFB and EFB diseases.

Changes of microorganism composition in fresh and stored bee pollen from Southern Germany

Analysis of plant pollen can provide valuable insights into the existing spectrum of microorganisms in the environment. When harvesting bee-collected pollen as a dietary supplement for human consumption, timely preservation of the freshly collected pollen is fundamental for product quality. Environmental microorganisms contained in freshly collected pollen can lead to spoilage by degradation of pollen components. In this study, freshly collected bee pollen was sampled at different locations and stored under various storage conditions to examine the hypothesis that storage conditions may have an effect on the composition of microorganisms in pollen samples. The samples were analyzed using 16S and 18S amplicon sequencing and characterized by palynological analysis. Interestingly, the bacterial communities between pollen samples from different locations varied only slightly, whereas for fungal community compositions, this effect was substantially increased. Further, we noticed that fungal communities in pollen are particularly sensitive to storage conditions. The fungal genera proportion Cladosporium and Mycosphaerella decreased, while Zygosaccharomyces and Aspergillus increased during storage. Aspergillus and Zygosaccharomyces fractions increased during storage at 30 °C, which could negatively impact the pollen quality if it is used as a dietary supplement.

Application of the Natural Products NOZEMAT HERB and NOZEMAT HERB PLUS Can Decrease Honey Bee Colonies Losses during the Winter

Honey bees (Apis mellifera L.) are crucial pollinators for many crops and natural ecosystems. However, honey bee colonies have been experiencing heavy overwinter mortality in almost all parts of the world. In the present study we have investigatеd, for the first time, the effects from the application of the herbal supplements NOZEMAT HERB® (NH) and NOZEMAT HERB PLUS® (NHP) on overwintering honey bee colony survival and on total protein and lysozyme content. To achieve this, in early autumn 2019, 45 colonies were selected and treated with these herbal supplements. The total protein and lysozyme content were evaluated after administration of NH and NHP twice the following year (June and September 2020). The obtained results have shown that both supplements have a positive effect on overwintering colony survival. Considerable enhancement in longevity of “winter bees” has been observed after the application of NHP, possibly due to the increased functionality of the immune system and antioxidant detoxification capacity. Although the mechanisms of action of NH and NHP are yet to be completely elucidated, our results suggest a new holistic approach on overwintering honey bee colony survival and welfare.

Compartmentalization of bacterial and fungal microbiomes in the gut of adult honeybees

The core gut microbiome of adult honeybee comprises a set of recurring bacterial phylotypes, accompanied by lineage-specific, variable, and less abundant environmental bacterial phylotypes. Several mutual interactions and functional services to the host, including the support provided for growth, hormonal signaling, and behavior, are attributed to the core and lineage-specific taxa. By contrast, the diversity and distribution of the minor environmental phylotypes and fungal members in the gut remain overlooked. In the present study, we hypothesized that the microbial components of forager honeybees (i.e., core bacteria, minor environmental phylotypes, and fungal members) are compartmentalized along the gut portions. The diversity and distribution of such three microbial components were investigated in the context of the physico-chemical conditions of different gut compartments. We observed that changes in the distribution and abundance of microbial components in the gut are consistently compartment-specific for all the three microbial components, indicating that the ecological and physiological interactions among the host and microbiome vary with changing physico-chemical and metabolic conditions of the gut.

The forgotten sugar: A review on multifarious applications of melezitose

Although, 187 years elapsed after the discovery of melezitose, it is a high time to deduce some solid applications as there are only 13 more years left to celebrate a double century of this sugar. The forgotten sugar has multifarious applications; it is used as a metabolic marker to differentiate melezitose fermenting microorganisms, as a carbon source to culture specific microorganisms, as a potential surfactant and excipient to stabilize pharmaceuticals, as a lyoprotectant or cryoprotectant for several industrial applications, as an edibility enhancer in food industry, as a hair smoothening agent in cosmetic industry, and provide protective & nourishing effects in fisheries and aquaculture industries. In entomological research, it is used to study niche differentiation, increased longevity of insects and also as a biocontrol agent. This review brings out the best possible applications of melezitose and present in the form of a mnemonic to remember this forgotten sugar.

Inter- and Intra-Species Diversity of Lactic Acid Bacteria in Apis mellifera ligustica Colonies

Lactic acid bacteria could positively affect the health of honey bees, including nutritional supplementation, immune system development and pathogen colonization resistance. Based on these considerations the present study evaluated predominant Lactic Acid Bacteria (LAB) species from beebread as well as from the social stomach and midgut of Apis mellifera ligustica honey bee foragers. In detail, for each compartment, the diversity in species and biotypes was ascertained through multiple culture-dependent approaches, consisting of Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE), 16S rRNA gene sequencing and Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). The study of a lactic acid bacteria community, performed with PCR-DGGE and sequence analysis targeting the V1-V3 region of the 16S rRNA gene (rDNA), highlighted the presence of a few species, including Apilactobacillus kunkeei, Lactiplantibacillus plantarum, Fructobacillus fructosus, Levilactobacillus brevis and Lactobacillus delbrueckii subsp. lactis. Depending on the different compartments, diverse levels of biodiversity in species were found. Particularly, a very low inter-species biodiversity was detected in the midgut that was prevalently dominated by the presence of Apilactobacillus kunkeei. On the other hand, the beebread was characterized by a reasonable biodiversity showing the presence of five species and the predominance of Apilactobacillus kunkeei, Lactiplantibacillus plantarum and Fructobacillus fructosus. The RAPD-PCR analysis performed on the three predominant species allowed the differentiation into several biotypes for each species. Moreover, a relationship between biotypes and compartments has been detected and each biotype was able to express a specific biochemical profile. The biotypes that populated the social stomach and midgut were able to metabolize sugars considered toxic for bees while those isolated from beebread could contribute to release useful compounds with functional properties. Based on this knowledge, new biotechnological approaches could be developed to improve the health of honey bees and the quality of bee products.

Antimicrobial Activity against Paenibacillus larvae and Functional Properties of Lactiplantibacillus plantarum Strains: Potential Benefits for Honeybee Health

Paenibacillus larvae is the causative agent of American foulbrood (AFB), a severe bacterial disease that affects larvae of honeybees. The present study evaluated, in vitro, antimicrobial activity of sixty-one Lactiplantibacillus plantarum strains, against P. larvae ATCC 9545. Five strains (P8, P25, P86, P95 and P100) that showed the greatest antagonism against P. larvae ATCC 9545 were selected for further physiological and biochemical characterizations. In particular, the hydrophobicity, auto-aggregation, exopolysaccharides production, osmotic tolerance, enzymatic activity and carbohydrate assimilation patterns were evaluated. The five L. plantarum selected strains showed suitable physical and biochemical properties for their use as probiotics in the honeybee diet. The selection and availability of new selected bacteria with good functional characteristics and with antagonistic activity against P. larvae opens up interesting perspectives for new biocontrol strategies of diseases such as AFB.