Bacteria help to increase bee colonies productivity (original) (raw)

Nowadays, honey bees are stressed by a number of biotic and abiotic factors which may compromise to some extent the pollination service and the hive productivity. The EU ban of antibiotics as therapeutic agents against bee pathogens has stimulated the search for natural alternatives. The increasing knowledge on the composition and functions of the bee gut microbiota and the link between a balanced gut microbiota and health status have encouraged the research on the use of gut microorganisms to improve bee health. Somehow, we are assisting to the transfer of the “probiotic concept” into the bee science. In this review, we examine the role of the honey bee gut microbiota in bee health and critically describe the available applications of beneficial microorganisms as pest control agents and health support. Most of the strains, mainly belonging to the genera Lactobacillus, Bifidobacterium and Bacillus, are isolated from honey bee crop or gut, but some applications involve environmental strains or formulation for animal and human consumption. Overall, the obtained results show the favourable effect of applied microbial strains on bee health and productivity, in particular if strains of bee origin are used. However, it is actually not yet possible to conclude whether this strategy will ever work. In particular, many aspects regarding the overall setup of the experiments, the dose, the timing and the duration of the treatment need to be optimized, also considering the microbiological safety of the hive products (i.e. pollen and honey). In addition, a deep investigation about the effect on host immunity and physiology is envisaged. Lastly, the final users of the formulations, i.e. beekeepers, should be taken into account for the achievement of high-quality, cost-effective and easy-to-use products.

"1. Animal hosts harbour diverse and often specific bacterial communities (“microbiota”) in their gut. These microbiota can provide crucial services to the host, such as aiding in digestion of food and immune defence. However, the ecological factors correlating with and eventually shaping these microbiota under natural conditions are poorly understood. 2. Bumble bees have recently been shown to possess simple and highly specific microbiota. We here examine the dynamics of these microbiota in field colonies of the bumble bee Bombus terrestris over one season. The gut bacteria were assessed with culture-independent methods, i.e. with terminal restriction fragment length profiles (TRFLPs) of the 16S rRNA gene. 3. To further understand the factors that affect the microbiota, we experimentally manipulated field-placed colonies in a fully factorial experiment by providing additional food, or by priming the workers’ immune system by injecting heat killed bacteria. We furthermore looked at possible correlates of diversity and composition of the microbiota for a) natural infections with the microbial parasites Crithidia bombi and Nosema bombi; b) bumble bee worker size; c) colony identity, and d) colony age. 4. We found an increase in diversity of the microbiota in individuals naturally infected with either C. bombi or N. bombi. C. bombi infections, however, appear to be only indirectly linked with higher microbial diversity when comparing colonies. The treatments of priming the immune system with heat-killed bacteria, and additional food supply, as well as host body size had no effect on the diversity or composition of the microbiota. Host colony identity had only a weak effect on the composition of the microbiota at the level of resolution of our method. We found both significant increases and decreases in the relative abundance of selected bacterial taxa over the season. 5. We present the first study on the ecological dynamics of gut microbiota in bumble bees and identify parasite infections, colony identity and colony age as important factors influencing the diversity and composition of the bacterial communities. The absence of an effect of our otherwise effective experimental treatments suggests a remarkable ability of the host to maintain a homeostasis in this community under widely different environments."

Honeybee health and the species’ gut microbiota are interconnected. Also noteworthy are the multiple niches present within hives, each with distinct microbiotas and all coexisting, which we termed “apibiome”. External stressors (e.g. anthropization) can compromise microbial balance and bee resilience. We hypothesised that (1) the bacterial communities of hives located in areas with different degrees of anthropization differ in composition, and (2) due to interactions between the multiple microbiomes within the apibiome, changes in the community of a niche would impact the bacteria present in other hive sections. We characterised the bacterial consortia of different niches (bee gut, bee bread, hive entrance and internal hive air) of 43 hives from 3 different environments (agricultural, semi-natural and natural) through 16S rRNA amplicon sequencing. Agricultural samples presented lower community evenness, depletion of beneficial bacteria, and increased recruitment of stress related pa...

Fungi are the leading cause of insect disease, contributing to the decline of wild and managed populations1,2. For ecologically and economically critical species, such as the European honey bee (Apis mellifera), the presence and prevalence of fungal pathogens can have far reaching consequences, endangering other species and threatening food security3,4,5. Our ability to address fungal epidemics and opportunistic infections is currently hampered by the limited number of antifungal therapies6,7. Novel antifungal treatments are frequently of bacterial origin and produced by defensive symbionts (bacteria that associate with an animal/plant host and protect against natural enemies 89. Here we examined the capacity of a honey bee-associated bacterium, Bombella apis, to suppress the growth of fungal pathogens and ultimately protect bee brood (larvae and pupae) from infection. Our results showed that strains of B. apis inhibit the growth of two insect fungal pathogens, Beauveria bassiana an...