Introduced bees (Osmia cornifrons) collect pollen from both coevolved and novel host-plant species within their family-level phylogenetic preferences

Studying the pollen preferences of introduced bees allows us to investigate how species use host-plants when establishing in new environments. Osmia cornifrons is a solitary bee introduced into North America from East Asia for pollination of Rosaceae crops such as apples and cherries. We investigated whether O. cornifrons (i) more frequently collected pollen from host-plant species they coevolved with from their geographic origin, or (ii) prefer host-plant species of specific plant taxa independent of origin. To address this question, using pollen metabarcoding, we examined the identity and relative abundance of pollen in larval provisions from nests located in different landscapes with varying abundance of East-Asian and non-Asian plant species. Our results show that O. cornifrons collected more pollen from plant species from their native range. Plants in the family Rosaceae were their most preferred pollen hosts, but they differentially collected species native to East Asia, Europe, or North America depending on the landscape. Our results suggest that while O. cornifrons frequently collect pollen of East-Asian origin, the collection of pollen from novel species within their phylogenetic familial affinities is common and can facilitate pollinator establishment. This phylogenetic preference highlights the effectiveness of O. cornifrons as crop pollinators of a variety of Rosaceae crops from different geographic origins. Our results imply that globalization of non-native plant species may ease the naturalization of their coevolved pollinators outside of their native range.

Susceptibility of Red Mason Bee Larvae to Bacterial Threats Due to Microbiome Exchange with Imported Pollen Provisions

Solitary bees are subject to a variety of pressures that cause severe population declines. Currently, habitat loss, temperature shifts, agrochemical exposure, and new parasites are identified as major threats. However, knowledge about detrimental bacteria is scarce, although they may disturb natural microbiomes, disturb nest environments, or harm the larvae directly. To address this gap, we investigated 12 Osmia bicornis nests with deceased larvae and 31 nests with healthy larvae from the same localities in a 16S ribosomal RNA (rRNA) gene metabarcoding study. We sampled larvae, pollen provisions, and nest material and then contrasted bacterial community composition and diversity in healthy and deceased nests. Microbiomes of pollen provisions and larvae showed similarities for healthy larvae, whilst this was not the case for deceased individuals. We identified three bacterial taxa assigned to Paenibacillus sp. (closely related to P. pabuli/amylolyticus/xylanexedens), Sporosarcina sp., and Bacillus sp. as indicative for bacterial communities of deceased larvae, as well as Lactobacillus for corresponding pollen provisions. Furthermore, we performed a provisioning experiment, where we fed larvae with untreated and sterilized pollens, as well as sterilized pollens inoculated with a Bacillus sp. isolate from a deceased larva. Untreated larval microbiomes were consistent with that of the pollen provided. Sterilized pollen alone did not lead to acute mortality, while no microbiome was recoverable from the larvae. In the inoculation treatment, we observed that larval microbiomes were dominated by the seeded bacterium, which resulted in enhanced mortality. These results support that larval microbiomes are strongly determined by the pollen provisions. Further, they underline the need for further investigation of the impact of detrimental bacterial acquired via pollens and potential buffering by a diverse pollen provision microbiome in solitary bees.

Abnormal neovascular and proliferative conjunctival phenotype in limbal stem cell deficiency is associated with altered microRNA and gene expression modulated by PAX6 mutational status in congenital aniridia

PURPOSE

To evaluate conjunctival cell microRNA (miRNAs) and mRNA expression in relation to observed phenotype of progressive limbal stem cell deficiency in a cohort of subjects with congenital aniridia with known genetic status.

METHODS

Using impression cytology, bulbar conjunctival cells were sampled from 20 subjects with congenital aniridia and 20 age and sex-matched healthy control subjects. RNA was extracted and miRNA and mRNA analyses were performed using microarrays. Results were related to severity of keratopathy and genetic cause of aniridia.

RESULTS

Of 2549 miRNAs, 21 were differentially expressed in aniridia relative to controls (fold change ≤ -1.5 or ≥ +1.5). Among these miR-204-5p, an inhibitor of corneal neovascularization, was downregulated 26.8-fold in severely vascularized corneas. At the mRNA level, 539 transcripts were differentially expressed (fold change ≤ -2 or ≥ +2), among these FOSB and FOS were upregulated 17.5 and 9.7-fold respectively, and JUN by 2.9-fold, all being components of the AP-1 transcription factor complex. Pathway analysis revealed enrichment of PI3K-Akt, MAPK, and Ras signaling pathways in aniridia. For several miRNAs and transcripts regulating retinoic acid metabolism, expression levels correlated with keratopathy severity and genetic status.

CONCLUSION

Strong dysregulation of key factors at the miRNA and mRNA level suggests that the conjunctiva in aniridia is abnormally maintained in a pro-angiogenic and proliferative state, and these changes are expressed in a PAX6 mutation-dependent manner. Additionally, retinoic acid metabolism is disrupted in severe, but not mild forms of the limbal stem cell deficiency in aniridia.

Existence of reprogrammed lymphoma stem cells in a murine ALCL-like model

While cancer stem cells are well established in certain hematologic and solid malignancies, their existence in T cell lymphoma is unclear and the origin of disease is not fully understood. To examine the existence of lymphoma stem cells, we utilized a mouse model of anaplastic large cell lymphoma. Established NPM-ALK⁺ lymphomas contained heterogeneous cell populations ranging from mature T cells to undifferentiated hematopoietic stem cells. Interestingly, CD4^-/CD8^- double negative (DN) lymphoma cells aberrantly expressed the T cell receptor α/β chain. Serial transplantation of sorted CD4/CD8 and DN lymphoma subpopulations identified lymphoma stem cells within the DN3/DN4 T cell population, whereas all other subpopulations failed to establish serial lymphomas. Moreover, transplanted lymphoma DN3/DN4 T cells were able to differentiate and gave rise to mature lymphoma T cells. Gene expression analyses unmasked stem-cell-like transcriptional regulation of the identified lymphoma stem cell population. Furthermore, these lymphoma stem cells are characterized by low CD30 expression levels, which might contribute to limited long-term therapeutic success in patients treated with anti-CD30-targeted therapies. In summary, our results highlight the existence of a lymphoma stem cell population in a NPM-ALK-driven CD30⁺ mouse model, thereby giving the opportunity to test innovative treatment strategies developed to eradicate the origin of disease.

Open Science principles for accelerating trait-based science across the Tree of Life

Synthesizing trait observations and knowledge across the Tree of Life remains a grand challenge for biodiversity science. Species traits are widely used in ecological and evolutionary science, and new data and methods have proliferated rapidly. Yet accessing and integrating disparate data sources remains a considerable challenge, slowing progress toward a global synthesis to integrate trait data across organisms. Trait science needs a vision for achieving global integration across all organisms. Here, we outline how the adoption of key Open Science principles-open data, open source and open methods-is transforming trait science, increasing transparency, democratizing access and accelerating global synthesis. To enhance widespread adoption of these principles, we introduce the Open Traits Network (OTN), a global, decentralized community welcoming all researchers and institutions pursuing the collaborative goal of standardizing and integrating trait data across organisms. We demonstrate how adherence to Open Science principles is key to the OTN community and outline five activities that can accelerate the synthesis of trait data across the Tree of Life, thereby facilitating rapid advances to address scientific inquiries and environmental issues. Lessons learned along the path to a global synthesis of trait data will provide a framework for addressing similarly complex data science and informatics challenges.

Floral Species Richness Correlates with Changes in the Nutritional Quality of Larval Diets in a Stingless Bee

Bees need food of appropriate nutritional quality to maintain their metabolic functions. They largely obtain all required nutrients from floral resources, i.e., pollen and nectar. However, the diversity, composition and nutritional quality of floral resources varies with the surrounding environment and can be strongly altered in human-impacted habitats. We investigated whether differences in plant species richness as found in the surrounding environment correlated with variation in the floral diversity and nutritional quality of larval provisions (i.e., mixtures of pollen, nectar and salivary secretions) composed by the mass-provisioning stingless bee Tetragonula carbonaria (Apidae: Meliponini). We found that the floral diversity of larval provisions increased with increasing plant species richness. The sucrose and fat (total fatty acid) content and the proportion and concentration of the omega-6 fatty acid linoleic acid decreased, whereas the proportion of the omega-3 fatty acid linolenic acid increased with increasing plant species richness. Protein (total amino acid) content and amino acid composition did not change. The protein to fat (P:F) ratio, known to affect bee foraging, increased on average by more than 40% from plantations to forests and gardens, while the omega-6:3 ratio, known to negatively affect cognitive performance, decreased with increasing plant species richness. Our results suggest that plant species richness may support T. carbonaria colonies by providing not only a continuous resource supply (as shown in a previous study), but also floral resources of high nutritional quality.

BCdatabaser: on-the-fly reference database creation for (meta-)barcoding

Summary

DNA barcoding and meta-barcoding have become irreplaceable in research and applications, where identification of taxa alone or within a mixture, respectively, becomes relevant. Pioneering studies were in the microbiological context, yet nowadays also plants and animals become targeted. Given the variety of markers used, formatting requirements for classifiers and constant growth of primary databases, there is a need for dedicated reference database creation. We developed a web and command-line interface to generate such on-the-fly for any applicable marker and taxonomic group with optional filtering, formatting and restriction specific for (meta-)barcoding purposes. Also, databases optionally receive a DOI, making them well-documented with meta-data, publicly sharable and citable.

Availability and implementation

source code: https://www.github.com/molbiodiv/bcdatabaser, webservice: https://bcdatabaser.molecular.eco, documentation: https://molbiodiv.github.io/bcdatabaser.

The genus Micromonospora as a model microorganism for bioactive natural product discovery

This review covers the development of the genus Micromonospora as a model for natural product research and the timeline of discovery progress from the classical bioassay-guided approaches through the application of genome mining and genetic engineering techniques that target specific products. It focuses on the reported chemical structures along with their biological activities and the synthetic and biosynthetic studies they have inspired. This survey summarizes the extraordinary biosynthetic diversity that can emerge from a widely distributed actinomycete genus and supports future efforts to explore under-explored species in the search for novel natural products.

We explore the genus Micromonospora as a model for natural product research and the discovery progress from the classical bioassay-guided approaches through to the application of genome mining and genetic engineering techniques that target specific products.

[Stereotactic radiotherapy of brain metastases in complex situations]

Stereotactic radiation therapy of brain metastases is a treatment recognized as effective, well tolerated, applicable for therapeutic indications codified and validated by national and international guidelines. However, the effectiveness of this irradiation, the evolution of patient care and the technical improvements enabling its implementation make it possible to consider it in more complex situations: proximity of brain metastases to organs at risk; large, cystic, haemorrhagic or multiple brain metastases, combination with targeted therapies and immunotherapy, stereotactic radiotherapy in patients with a pacemaker. This article aims to put forward the arguments available to date in the literature and those resulting from clinical practice to provide decision support for the radiation oncologists.

Linking pollen foraging of megachilid bees to their nest bacterial microbiota

Solitary bees build their nests by modifying the interior of natural cavities, and they provision them with food by importing collected pollen. As a result, the microbiota of the solitary bee nests may be highly dependent on introduced materials. In order to investigate how the collected pollen is associated with the nest microbiota, we used metabarcoding of the ITS2 rDNA and the 16S rDNA to simultaneously characterize the pollen composition and the bacterial communities of 100 solitary bee nest chambers belonging to seven megachilid species. We found a weak correlation between bacterial and pollen alpha diversity and significant associations between the composition of pollen and that of the nest microbiota, contributing to the understanding of the link between foraging and bacteria acquisition for solitary bees. Since solitary bees cannot establish bacterial transmission routes through eusociality, this link could be essential for obtaining bacterial symbionts for this group of valuable pollinators.

OPEN RESEARCH BADGES

This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://www.ebi.ac.uk/ena/data/view/PRJEB27223, https://www.ebi.ac.uk/ena/data/view/PRJEB31610, and https://doi.org/10.5061/dryad.qk36k8q.

B-75 A Preliminary Investigation of Predictors of Employment and Perception of Ability to Work in Combat-Exposed Veterans

Objective

The purpose of this study was twofold: (1) to evaluate whether perception of one’s ability to work (a subjective rating) predicts employment status (an objective marker of functioning) in a sample of combat-exposed Veterans, and (2) to examine predictors of employment status and perception of work ability to determine whether the same sets of variables that predict employment status also predict perception of one’s ability to work.

Method

Combat-exposed Operation Enduring Freedom/Operation Iraqi Freedom Veterans (N = 83) completed self-report questionnaires assessing demographic characteristics, combat-related experiences, and psychiatric and neurobehavioral/health-related symptoms. Veterans also underwent a comprehensive neuropsychological assessment. Primary outcomes of interest were employment status (unemployed versus employed) and Veterans’ rating of a perceived decline in work ability (yes versus no).

Results

Logistic regression analyses showed that perception of work ability significantly predicted employment status (p = .046). Moreover, psychiatric and neurobehavioral/health-related symptoms significantly predicted employment status and perception of work ability (p = .001-.017), whereas demographic characteristics (i.e., service-connection disability rating) and combat-related experiences (i.e., number of traumatic brain injuries) only predicted perception of work ability (p = .010-.029). Cognition was not significantly associated with employment status or perception of work ability (p’s > .05).

Conclusions

Altogether, these findings support the notion that perception of one’s ability to work plays an important role in employment-related outcomes in combat-exposed Veterans. Future studies using larger samples are needed to confirm these findings, but our preliminary results suggest that perception of work ability may be a particularly important treatment target in this population.

Effects of Multiple Mild TBIs on Neuropsychological Functioning, Psychiatric Symptoms, and Neurobehavioral/Health-Related Symptoms in Combat-Exposed Veterans

Objective

The purpose of this study was to examine the influence of multiple mild traumatic brain injuries (mTBI) on objective neuropsychological functioning and subjective symptom reporting in a sample of combat-exposed Veterans.

Method

Participants included 80 combat-exposed Iraq/Afghanistan Veterans (91.3% male; age: M = 34.33, SD = 6.44) divided into three groups based on mTBI history: 0 mTBIs (n = 33), 1-2 mTBIs (n = 26), and 3+ mTBIs (n = 21). Veterans with mTBI were assessed, on average, 7.5 years following their most recent mTBI. Participants underwent comprehensive neuropsychological testing and completed self-report measures assessing psychiatric and neurobehavioral/health-related symptoms.

Results

ANCOVAs adjusting for level of combat exposure showed no group differences on the memory and attention/executive functioning composite scores (p’s>.05). Additionally, groups did not differ with respect to symptoms of posttraumatic stress and depression (p’s>.05). In contrast, there were significant group differences on all neurobehavioral/health-related symptoms, including post-concussive symptom clusters (p’s < .001-.005), sleep problems (p = .024), pain symptoms (p < .001), and pain catastrophizing (p = .049). In general, Veterans with 3+ mTBIs self-reported the most severe symptoms, followed by Veterans with 1-2 mTBIs and 0 mTBIs.

Conclusions

History of multiple, remote mTBIs is associated with elevated subjective neurobehavioral/health-related symptoms in a dose-dependent fashion, but is not associated with objective neuropsychological functioning or ratings of psychiatric distress in combat-exposed Veterans. These results advance understanding of the long-term consequences of multiple mTBIs in this population and suggest that Veterans with 3 or more mTBIs may especially benefit from (1) early treatments aimed at ameliorating sleep and pain symptoms and (2) therapies that provide tools to temper catastrophic thinking about these symptoms.

The Role of Potentially Malleable Factors in Post-Concussive Symptoms and Objective Cognitive Outcomes in Iraq and Afghanistan Veterans with History of Mild TBI

Objective

We examined whether potentially malleable factors are associated with post-concussive symptoms (PCS) and cognition in Veterans with mild traumatic brain injury (mTBI) histories.

Method

Combat-exposed Iraq and Afghanistan Veterans with remote history of mTBI (N=48) completed a neuropsychological assessment and self-report questionnaires. Hierarchical linear regressions predicting PCS (Rivermead Post-Concussion Symptoms Questionnaire) and objective cognition included relevant demographic, injury, and psychiatric symptom variables in the first block and five malleable factors (TBI knowledge, self-efficacy, coping style, attribution of symptoms to mTBI, and uncommonly-endorsed symptoms [mild Brain Injury Atypical Symptoms (mBIAS) scale]) in the second block. Those with valid performance validity tests (n = 42) were included in the cognitive test analyses.

Results

With psychiatric symptoms and lifetime history of mTBIs entered first, malleable factors accounted for 14-17% of additional variance in PCS (p < .001). Lower self-efficacy (B = -.53, p < .001) and greater attribution of symptoms to mTBI (B = .21, p = .05) were associated with higher PCS, whereas an approach style of coping, TBI knowledge, and the mBIAS were not (p’s>.05). Regarding cognition, the malleable factors block accounted for 25% of additional variance in executive functioning (p = .04) with premorbid intelligence entered first. Specifically, higher mBIAS scores significantly predicted worse executive functioning (B = -.50, p = .004). No significant associations emerged when predicting attention/processing speed or memory (p’s>.05).

Conclusions

In combat-exposed Veterans with mTBI histories, potentially malleable factors contribute to clinical outcomes even after accounting for psychiatric symptoms. These malleable features are prime targets to augment during psychoeducation (e.g., uncommonly-endorsed symptoms, attribution of symptoms) and cognitive behavioral therapy (e.g., self-efficacy) in the context of chronic PCS.

A-18 Executive Dysfunction is Associated with Suicidal Ideation in Iraq/Afghanistan-era Combat-exposed Veterans

Objective

Suicidal ideation (SI) is highly prevalent in Veterans and reducing Veteran suicide is a national priority. The present study examined factors associated with SI in combat-exposed Veterans in order to inform suicide prevention efforts.

Method

Combat-exposed Iraq/Afghanistan-era Veterans (N = 77) completed questionnaires detailing demographic characteristics and combat-related experiences, as well as structured interviews assessing history of mild traumatic brain injury (mTBI), current posttraumatic stress disorder (PTSD), and suicidality in the past month. Veterans also underwent a comprehensive neuropsychological assessment. Analyses examined differences between endorsers versus non-endorsers of current SI, as well as predictors of SI, with a focus on cognitive variables.

Results

There were no SI group differences in demographic variables, levels of combat exposure, or rates of PTSD, or mTBI history. However, independent samples t-tests indicated that those who endorsed SI demonstrated worse executive functioning relative to those who denied SI (t(75) = 2.74, p = .008), whereas no group differences were observed on measures of attention/processing speed or memory. A logistic regression analysis predicting SI indicated that executive functioning remained a significant predictor of SI (B = .94, OR = 2.55, p = .047) even when adjusting for age, years of education, level of combat exposure, history of mTBI, and PTSD diagnosis.

Conclusions

Executive dysfunction may make it difficult for Veterans to inhibit maladaptive negative thoughts (particularly suicidal thoughts), regulate emotions, and problem solve in stressful situations, thus contributing to suicidality. Interventions addressing executive dysfunction in combat-exposed Veterans with SI may be a promising adjunct to current suicide prevention efforts.

Drivers, Diversity, and Functions of the Solitary-Bee Microbiota

Accumulating reports of global bee declines have drawn much attention to the bee microbiota and its importance. Most research has focused on social bees, while solitary species have received scant attention despite their enormous biodiversity, ecological importance, and agroeconomic value. We review insights from several recent studies on diversity, function, and drivers of the solitary-bee microbiota, and compare these factors with those relevant to the social-bee microbiota. Despite basic similarities, the social-bee model, with host-specific core microbiota and social transmission, is not representative of the vast majority of bee species. The solitary-bee microbiota exhibits greater variability and biodiversity, with a strong impact of environmental acquisition routes. Our synthesis identifies outstanding questions that will build understanding of these interactions, responses to environmental threats, and consequences for health.

Gain of 20q11.21 in Human Pluripotent Stem Cells Impairs TGF-β-Dependent Neuroectodermal Commitment

Gain of 20q11.21 is one of the most common recurrent genomic aberrations in human pluripotent stem cells. Although it is known that overexpression of the antiapoptotic gene Bcl-xL confers a survival advantage to the abnormal cells, their differentiation capacity has not been fully investigated. RNA sequencing of mutant and control hESC lines, and a line transgenically overexpressing Bcl-xL, shows that overexpression of Bcl-xL is sufficient to cause most transcriptional changes induced by the gain of 20q11.21. Moreover, the differentially expressed genes in mutant and Bcl-xL overexpressing lines are enriched for genes involved in TGF-β- and SMAD-mediated signaling, and neuron differentiation. Finally, we show that this altered signaling has a dramatic negative effect on neuroectodermal differentiation, while the cells maintain their ability to differentiate to mesendoderm derivatives. These findings stress the importance of thorough genetic testing of the lines before their use in research or the clinic.

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Bcl-xL overexpression drives the transcriptomic profile of 20q11.21 mutant lines

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20q11.21 mutant lines downregulate CHCHD2, a known TGF-β pathway modulator

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Mutant lines differentially express genes involved in TGF-β and SMAD signaling

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Mutant lines show impaired ectoderm commitment due to TGF-β signaling deregulation

Systematic Affiliation and Genome Analysis of Subtercola vilae DB165T with Particular Emphasis on Cold Adaptation of an Isolate from a High-Altitude Cold Volcano Lake

Among the Microbacteriaceae the species of Subtercola and Agreia form closely associated clusters. Phylogenetic analysis demonstrated three major phylogenetic branches of these species. One of these branches contains the two psychrophilic species Subtercola frigoramans and Subtercola vilae, together with a larger number of isolates from various cold environments. Genomic evidence supports the separation of Agreia and Subtercola species. In order to gain insight into the ability of S. vilae to adapt to life in this extreme environment, we analyzed the genome with a particular focus on properties related to possible adaptation to a cold environment. General properties of the genome are presented, including carbon and energy metabolism, as well as secondary metabolite production. The repertoire of genes in the genome of S. vilae DB165^T linked to adaptations to the harsh conditions found in Llullaillaco Volcano Lake includes several mechanisms to transcribe proteins under low temperatures, such as a high number of tRNAs and cold shock proteins. In addition, S. vilae DB165^T is capable of producing a number of proteins to cope with oxidative stress, which is of particular relevance at low temperature environments, in which reactive oxygen species are more abundant. Most important, it obtains capacities to produce cryo-protectants, and to combat against ice crystal formation, it produces ice-binding proteins. Two new ice-binding proteins were identified which are unique to S. vilae DB165^T. These results indicate that S. vilae has the capacity to employ different mechanisms to live under the extreme and cold conditions prevalent in Llullaillaco Volcano Lake.

Venus flytrap microbiotas withstand harsh conditions during prey digestion

The carnivorous Venus flytrap (Dionaea muscipula) overcomes environmental nutrient limitation by capturing small animals. Such prey is digested with an acidic enzyme-containing mucilage that is secreted into the closed trap. However, surprisingly little is known about associations with microorganisms. Therefore, we assessed microbiotas of traps and petioles for the Venus flytrap by 16S amplicon meta-barcoding. We also performed time-series assessments of dynamics during digestion in traps and experimental acidification of petioles. We found that the traps hosted distinct microbiotas that differed from adjacent petioles. Further, they showed a significant taxonomic turnover during digestion. Following successful catches, prey-associated bacteria had strong effects on overall composition. With proceeding digestion, however, microbiotas were restored to compositions resembling pre-digestion stages. A comparable, yet less extensive shift was found when stimulating digestion with coronatine. Artificial acidification of petioles did not induce changes towards trap-like communities. Our results show that trap microbiota were maintained during digestion despite harsh conditions and recovered after short-term disturbances through prey microbiota. This indicates trap-specific and resilient associations. By mapping to known genomes, we predicted putative adaptations and functional implications for the system, yet direct mechanisms and quantification of host benefits, like the involvement in digestion, remain to be addressed.

Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides)

Multihost infectious disease outbreaks have endangered wildlife, causing extinction of frogs and endemic birds, and widespread declines of bats, corals, and abalone. Since 2013, a sea star wasting disease has affected >20 sea star species from Mexico to Alaska. The common, predatory sunflower star (Pycnopodia helianthoides), shown to be highly susceptible to sea star wasting disease, has been extirpated across most of its range. Diver surveys conducted in shallow nearshore waters (n = 10,956; 2006-2017) from California to Alaska and deep offshore (55 to 1280 m) trawl surveys from California to Washington (n = 8968; 2004-2016) reveal 80 to 100% declines across a ~3000-km range. Furthermore, timing of peak declines in nearshore waters coincided with anomalously warm sea surface temperatures. The rapid, widespread decline of this pivotal subtidal predator threatens its persistence and may have large ecosystem-level consequences.

Wild bees and their nests host Paenibacillus bacteria with functional potential of avail

BACKGROUND

In previous studies, the gram-positive firmicute genus Paenibacillus was found with significant abundances in nests of wild solitary bees. Paenibacillus larvae is well-known for beekeepers as a severe pathogen causing the fatal honey bee disease American foulbrood, and other members of the genus are either secondary invaders of European foulbrood or considered a threat to honey bees. We thus investigated whether Paenibacillus is a common bacterium associated with various wild bees and hence poses a latent threat to honey bees visiting the same flowers.

RESULTS

We collected 202 samples from 82 individuals or nests of 13 bee species at the same location and screened each for Paenibacillus using high-throughput sequencing-based 16S metabarcoding. We then isolated the identified strain Paenibacillus MBD-MB06 from a solitary bee nest and sequenced its genome. We did find conserved toxin genes and such encoding for chitin-binding proteins, yet none specifically related to foulbrood virulence or chitinases. Phylogenomic analysis revealed a closer relationship to strains of root-associated Paenibacillus rather than strains causing foulbrood or other accompanying diseases. We found anti-microbial evidence within the genome, confirmed by experimental bioassays with strong growth inhibition of selected fungi as well as gram-positive and gram-negative bacteria.

CONCLUSIONS

The isolated wild bee associate Paenibacillus MBD-MB06 is a common, but irregularly occurring part of wild bee microbiomes, present on adult body surfaces and guts and within nests especially in megachilids. It was phylogenetically and functionally distinct from harmful members causing honey bee colony diseases, although it shared few conserved proteins putatively toxic to insects that might indicate ancestral predisposition for the evolution of insect pathogens within the group. By contrast, our strain showed anti-microbial capabilities and the genome further indicates abilities for chitin-binding and biofilm-forming, suggesting it is likely a useful associate to avoid fungal penetration of the bee cuticula and a beneficial inhabitant of nests to repress fungal threats in humid and nutrient-rich environments of wild bee nests.