Gut microbiome dysbiosis and honeybee health

Since a few decades, apiculture is facing important economic losses worldwide with general major consequences in many areas of agriculture. A strong attention has been paid towards the phenomenon named Colony Collapse Disorder in which colonies suddenly disappear with no clear explanations. Honeybee colonies can be affected by abiotic factors, such as environmental pollution or insecticide applications for agricultural purposes. Also biotic stresses cause colony losses, including bacterial (e.g. Paenibacillus larvae) and fungal (e.g. Ascosphaera apis) pathogens, microsporidia (e.g. Nosema apis), parasites (i.e. Varroa destructor) and several viruses. In the light of recent research, intestinal dysbiosis, considered as the relative disproportion of the species within the native microbiota, has shown to affect human and animal health. In arthropods, alteration of the gut microbial climax community has been shown to be linked to health and fitness disequilibrium, like in the medfly Ceratitis capitata for which low mate competitiveness is determined by a gut microbial community imbalance. According to these observations, it is possible to hypothesize that dysbiosis may have a role in disease occurrence also in honeybees. Here we aim to discuss the current knowledge on dysbiosis in the honeybee and its relation with honeybee health by reviewing the investigations of the microbial diversity associated to honeybees and the recent experiments performed to control bee diseases by microbial symbionts. We conclude that, despite the importance of a good functionality of the associated microbiota in preserving insect health has been proved, the mechanisms involved in honeybee gut dysbiosis are still unknown. Accurate in vitro, in vivo and in field investigations are required under healthy, diseased and stressed conditions for the host.     

Analysis of Conserved Glutamate and Aspartate Residues in Drosophila Rhodopsin 1 and Their Influence on Spectral Tuning

The molecular mechanisms that regulate invertebrate visual pigment absorption are poorly understood. Studies of amphioxus G_o-opsin have demonstrated that Glu-181 functions as the counterion in this pigment. This finding has led to the proposal that Glu-181 may function as the counterion in other invertebrate visual pigments as well. Here we describe a series of mutagenesis experiments to test this hypothesis and to also test whether other conserved acidic amino acids in Drosophila Rhodopsin 1 (Rh1) may serve as the counterion of this visual pigment. Of the 5 Glu and Asp residues replaced by Gln or Asn in our experiments, none of the mutant pigments shift the absorption of Rh1 by more than 6 nm. In combination with prior studies, these results suggest that the counterion in Drosophila Rh1 may not be located at Glu-181 as in amphioxus, or at Glu-113 as in bovine rhodopsin. Conversely, the extremely low steady state levels of the E194Q mutant pigment (bovine opsin site Glu-181), and the rhabdomere degeneration observed in flies expressing this mutant demonstrate that a negatively charged residueat this position is essential for normal rhodopsin function in vivo. This work also raises the possibility that another residue or physiologic anion may compensate for the missing counterion in the E194Q mutant.     

Antimicrobial activity of [2-(methacryloyloxy)ethyl]trimethylammonium chloride against Candida spp

BackgroundCandida-associated denture stomatitis is the most common manifestation of oral candidal infection, caused mainly by Candida albicans. Several authors have attempted to add antifungal agents or antiseptics to denture temporary soft lining materials or to denture acrylic resins, without relevant results. Therefore, the investigation of a quaternary ammonium functionalized compound [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT), which copolymerizes with methacrylates and which could act as a fungal inhibitor, is of paramount importance.AimsTo evaluate the in vitro activity of MADQUAT against Candida species.MethodsThirty-one Candida strains were used to determine the in vitro antifungal activity of this compound. The minimum inhibitory concentrations and minimum fungicidal concentrations of MADQUAT and nystatin were determined.ResultsMADQUAT showed antifungal properties at concentrations of 6.25 to > 100 mg/ml, and fungicidal activity between 25 and > 100 mg/ml. The quantitative determinations of the fungistatic and fungicidal activity of MADQUAT showed fungistatic activity against all Candida albicans, Candida krusei and Candida parapsilosis strains, revealing fungicidal activity against some strains of the other species.ConclusionsMADQUAT has antifungal activity against Candida spp. Moreover, the sensitivity to this substance varies across the different species in terms of MIC values and fungicidal or fungistatic activity.     

Population structure and Mdh-1 locus variation in Apis mellifera ligustica

In a wide area of the Piedmont of Italy the apiaries of Apis mellifera ligustica Spin., (the Italian bee) show homogeneous allelic frequency distributions at the Mdh-1 locus, the only one known to be polymorphic in worker bees. This can be explained by considering that an apiary is not a closed genetic system and that among apiaries gene flow is sufficient to overcome the different forces of inbreeding and random genetic drift. Nevertheless there is some evidence for partial subdivision because the pooled samples show a weak Wahlund effect. Moreover, the M allele at the same locus can be used as a diagnostic marker to distinguish A. m. ligustica populations (M absent or at very low frequencies) from A. m. mellifera French populations (monomorphic for M). The two honey-bee varieties, almost entirely separated by the Alps, hybridize with each other in very limited alpine areas. Hybrid populations show intermediate M frequencies.