The gut microbiome of solitary bees is mainly affected by pathogen assemblage and partially by land use

Abstract

Pollinators, including solitary bees, are drastically declining worldwide. Among the factors contributing to this decline, bee pathogens and different land uses are of relevance. The link between the gut microbiome composition and host health has been recently studied for social pollinators (e.g. honeybees), whereas the information related to solitary bees is sparse. This work aimed at the characterization of the gut microbiome of the solitary bees Xylocopa augusti, Eucera fervens and Lasioglossum and attempted to correlate the gut microbial composition with the presence and load of different pathogens and land uses. Solitary bees were sampled in different sites (i.e. a farm, a natural reserve, and an urban plant nursery) showing different land uses. DNA was extracted from the gut, 16S rRNA gene amplified and sequenced. Eight pathogens, known for spillover from managed bees to wild ones, were quantified with qPCR. The results showed that the core microbiome profile of the three solitary bees significantly varied in the different species. Pseudomonas was found as the major core taxa in all solitary bees analyzed, whereas Lactobacillus, Spiroplasma and Sodalis were the second most abundant taxa in X. augusti, E. fervens and Lasioglossum, respectively. The main pathogens detected with qPCR were Nosema ceranae, Nosema bombi and Crithidia bombi, although differently abundant in the different bee species and sampling sites. Most microbial taxa did not show any correlation with the land use, apart from Snodgrassella and Nocardioides, showing higher abundances on less anthropized sites. Conversely, the pathogens species and load strongly affected the gut microbial composition, with Bifidobacterium, Apibacter, Serratia, Snodgrassella and Sodalis abundance that positively or negatively correlated with the detected pathogens load. Therefore, pathogens presence and load appear to be the main factor shaping the gut microbiome of solitary bees in Argentina.

Microbial Diversity in Bee Species and Bee Products: Pseudomonads Contribution to Bee Well-Being and the Biological Activity Exerted by Honey Bee Products: A Narrative Review

“…However, in a study, Pseudomonads in solitary bees were the most represented bacteria, with Lasioglossium, Xylocopa augusti, and Eucera fervens being prevalent in the gut microbiome, with average relative abundances of 39.84%, 36.05%, and 50.91%, respectively [128].…”

“…It has been shown that the gut bacteria Serratia and Pseudomonas contribute to atrazine (herbicide) degradation. Both of these bacteria have atrazine-degradation-related genes, which conferred resistance in an experimentally exposed wasp population [128,142]. The genes and corresponding enzymes involved in atrazine degradation by a Pseudomonas sp.…”

The untapped potential of cell culture in disentangling insect-microbial relationships

“…This principle applies well to social insect species, which possess highly conserved and vertically transmitted microbiome compositions [ 86 , 87 ] . However, the theory fails to consider solitary insect microbiomes, which more often mimic the composition of their environment [ 6 , 88 ] . Other researchers have argued that the level of connectedness determines the health of the microbiome, rather than the balance of species [ 84 ] .…”

Bee-Associated Beneficial Microbes—Importance for Bees and for Humans

“…Regarding the microbiota of solitary bees, this is an entirely diverse topic and is a factor modulating host health and development. De Landa et al [ 47 ] reported that the gut microbiome of solitary bees ( Xylocopa augusti , Eucera fervens , and Lasioglossum spp.) is associated with the presence of species such as Pseudomonas as the major core taxa in all species analyzed, whereas other, such as lactobacilli, Spiroplasma , and Sodalis , were the second most abundant taxa.…”