Biology subjects

Engl, T.

Publications and source records attributed to Engl, T..

7 recordsLinked to original sources

bioRxiv2026

Diffuse fungal symbiosis in Deathwatch beetles

Many insects rely on symbiotic fungi to occupy specialized ecological niches, yet the evolutionary dynamics of these partnerships remain poorly resolved for most lineages. The beetle family Ptinidae, split into the morphologically distinct Spider beetles and Deathwatch beetles, has long been known to harbor fungal endosymbionts based on early microscopy, but few associations have been confirmed with molecular methods. Here, we combined ultra-conserved element (UCE) phylogenomics with ITS amplicon sequencing to test whether fungal endosymbionts are conserved across Ptinidae and whether they have cospeciated with their hosts. Our UCE phylogeny supports Spider beetles and Deathwatch beetles as monophyletic clades but indicates that some aspects of subfamily-level taxonomy may merit closer examination. Screening for three known symbiotic fungal genera (Symbiotaphrina, Meyerozyma, Nakazawaea) revealed Symbiotaphrina in most Deathwatch beetles but no Spider beetles, while the other two genera were present but uncommon. Despite widespread Symbiotaphrina infection, we found no phylogenetic mirroring between host and symbiont trees, indicating an absence of codiversification. Instead, distantly related hosts frequently shared closely related symbionts, consistent with diffuse, mixed-mode transmission involving both vertical and horizontal symbiont exchange. This pattern parallels those documented in fungus-farming termites, ambrosia beetles, ants, and woodwasps, suggesting that diffuse, mixed-mode symbiosis may be a general hallmark of long-term insect-fungal associations. We further identify an unidentified Helotiales group as a candidate novel endosymbiont, recovered consistently within a clade comprising Anobium, Hemicoelus, and Ptilinus. Together, these findings reframe Deathwatch beetle-fungal associations as a dynamic, evolutionarily labile symbiosis rather than a fixed partnership.

microbiology↗

bioRxiv2025

Metabolic plasticity supports a flexible nutritional symbiosis in Cardiocondyla ants

Nutritional symbioses have repeatedly evolved in insects, yet how hosts regulate these partnerships to balance benefits across development and environments remains unclear. Ants provide an exceptional system to address this question, as several lineages maintain ancient symbionts that can be naturally lost without harming the host. Using Cardiocondyla obscurior, which carries and occasionally loses the vertically transmitted symbiont Cand. Westeberhardia cardiocondylae, we reveal the regulatory dynamics and function of this labile association. Symbionts provide shikimate-derived nutrients that enhance colony resilience under protein limitation, while hosts actively regulate symbiont abundance during protein scarcity and cuticle formation to optimise resource allocation. In the symbionts absence, ants compensate by upregulating genes enabling tyrosine acquisition from external sources. This metabolic flexibility allows colonies to exploit symbiont-derived and environmental nutrients, sustaining both growth and survival across nutritional contexts. Our findings reveal dynamic host regulation as a mechanism sustaining the persistence and adaptability of ancient symbioses.

ecology↗

bioRxiv2025

A multi-partner symbiotic community inhabits the emerging pest Pentastiridius leporinus

The planthopper Pentastiridius leporinus has emerged as a severe crop pest, rapidly expanding both its host plant range and the affected areas in central Europe. Originating as a monophagous herbivore of reed grass, P. leporinus recently adopted polyphagous feeding and is now a pest of sugar beet, potato, carrot, and onion, suggesting rapid ecological niche expansion. P. leporinus vectors two bacterial pathogens, the {gamma}-proteobacterium Candidatus Arsenophonus phytopathogenicus (CAP) and the stolbur phytoplasma Candidatus Phytoplasma solani (CPS), which are responsible for a range of disease syndromes, including syndrome basses richesses (SBR) in sugar beet. We used long-read metagenomic sequencing to characterize the genomes of microbes associated with P. leporinus, resulting in the complete sequences of CAP and CPS, as well as primary symbionts of the genera Purcelliella, Sulcia and Vidania, and facultative symbionts Rickettsia and Wolbachia. The primary symbionts are inferred to provide all ten essential amino acids and contribute to B vitamin biosynthesis. The genomes of CPS and CAP encode numerous pathogenicity factors, enabling the colonization of different hosts. Bacterial fluorescence in situ hybridization revealed the tissue distribution, cellular localization, relative abundance and transmission patterns of these bacteria. The intracellular presence of all primary symbionts in bacteriomes, the intracellular presence of Wolbachia, and the intranuclear localization of Rickettsia, suggest vertical transmission. CPS was restricted to salivary glands, suggesting strict horizontal, plant-mediated transmission, whereas CAP colonized all tissue types, allowing for horizontal and vertical transmission. Our data suggest that P. leporinus hosts an exceptionally broad range of symbionts, encompassing mutualistic, commensal and pathogenic interactions. ImportanceThe planthopper Pentastiridius leporinus has recently expanded its host plant range and emerged as severe pest of sugar beet and potato crops in central Europe, which is exacerbated by its capacity to vector bacterial pathogens to its host plants. Because microbial symbionts may play an important role for both the host plant shifts and the transmission of pathogens, we used metagenomic sequencing and fluorescence in situ hybridization to characterize the microbial community associated with P. leporinus. We detected three bacteriome-localized primary symbionts that together provision all essential amino acids and several B-vitamins to the host, as well as two intracellular bacteria with a broader tissue distribution. In addition, we infer localization, transmission, and putative pathogenicity factors for the two major phytopathogens that are vectored by P. leporinus. Our results reveal a complex community of symbiotic bacteria that likely shapes the interaction of this emerging pest with its host plants.

systems biology↗

bioRxiv2024

The bacterial microbiome in Spider and Deathwatch beetles

The beetle family Ptinidae contains a number of economically important pests, such as the Cigarette beetle Lasioderma serricorne, the Drugstore beetle Stegobium paniceum, and the diverse Spider beetles. Many of these species are stored product pests which target a diverse range of food sources from dried tobacco to books made with organic materials. Despite the threat that the 2,200 species of Ptinidae beetles pose, fewer than 50 have been surveyed for microbial symbionts, and only a handful have been screened using contemporary genomic methods. In this study, we screen 116 individual specimens that cover most subfamilies of Ptinidae, with outgroup beetles from closely related families Dermestidae, Endecatomidae, and Bostrichidae. We used 16S ribosomal RNA gene amplicon data to characterize the bacterial microbiomes of these specimens. The majority of these species had never been screened for microbes. We found that, unlike in their sister family Bostrichidae that has two mutualistic bacteria seen in most species, there are no consistent bacterial members of ptinid microbiomes. For specimens which had Wolbachia infections, we did additional screening using multilocus sequence typing, and showed that our populations have different strains of Wolbachia than has been noted in previous publications. ImportancePtinid beetles are both household pests of pantry goods and economic pests of dried good warehouses and cultural archives such as libraries and museums. Currently, the most common pest control measures for ptinid beetles are phosphine and/or heat treatments. Many ptinid beetles have been observed to have increasing resistance to phosphine, and heat treatments are not appropriate for many of the goods commonly infested by ptinids. Pest control techniques focused on symbiotic bacteria have been shown to significantly decrease populations, and often have the beneficial side effect of being more specific than other pest control techniques. This survey provides foundational information about the bacteria associated with diverse ptinid species, which may be used for future control efforts.

microbiology↗

bioRxiv2022

Cuticle supplementation and nitrogen recycling by a dual bacterial symbiosis in a family of xylophagous beetles (Coleoptera: Bostrichidae)

Many insects engage in stable nutritional symbioses with bacteria that supplement limiting essential nutrients to their host. While several plant sap-feeding Hemipteran lineages are known to be simultaneously associated with two or more endosymbionts with complementary biosynthetic pathways to synthesize amino acids or vitamins, such co-obligate symbioses have not been functionally characterized in other insect orders. Here, we report on the characterization of a dual co-obligate, bacteriome-localized symbiosis in a family of xylophagous beetles using comparative genomics, fluorescence microscopy, and phylogenetic analyses. Across the beetle family Bostrichidae, all investigated species harbored the Bacteroidota symbiont Shikimatogenerans bostrichidophilus that encodes the shikimate pathway to produce tyrosine precursors in its severely reduced genome, likely supplementing the beetles cuticle biosynthesis, sclerotisation, and melanisation. One clade of Bostrichid beetles additionally housed the co-obligate symbiont Bostrichicola ureolyticus that is inferred to complement the function of Shikimatogenerans by recycling urea and provisioning the essential amino acid lysine, thereby providing additional benefits on nitrogen-poor diets. Both symbionts represent ancient associations within the Bostrichidae that have subsequently experienced genome erosion and co-speciation with their hosts. While Bostrichicola was repeatedly lost, Shikimatogenerans has been retained throughout the family and exhibits a perfect pattern of co-speciation. Our results reveal that co-obligate symbioses with complementary metabolic capabilities occur beyond the well-known sap-feeding Hemiptera and highlight the importance of symbiont-mediated cuticle supplementation and nitrogen recycling for herbivorous beetles. Significance statementNutritional symbioses evolved frequently in insects and contribute diverse metabolites to their hosts physiology. Associations with dual symbionts providing complementary nutrients evolved in multiple Hemiptera lineages, compensating eroded biosynthetic capabilities of primary symbionts. Bostrichidae, a family of xylophagous beetles, harbor consistently a Flavobacterial symbiont encoding exclusively the Shikimate pathway to synthesis precursors of tyrosine. However, in two families a second, closely Flavobacterial symbiont capable of recycling urea and synthesizing lysine was retained. Both symbionts exhibit high genomic syntheny and tight co-cladogenesis with the host phylogeny, indicating ancestral, ecological highly beneficial symbioses.

evolutionary biology↗

bioRxiv2018

Nitric oxide radicals are emitted by wasp eggs to kill mold fungi

Detrimental microbes caused the evolution of a great diversity of antimicrobial defenses in plants and animals. Here we show that the eggs of a solitary digger wasp, the European beewolf Philanthus triangulum, emit large amounts of the gaseous free radical nitric oxide (NO{dot}) to protect themselves and their provisions, paralyzed honeybees, against mold fungi. Despite the extraordinary concentrations of nitrogen radicals (NO{dot} and its oxidation product NO2{dot}) in the brood cells (~1500ppm), NO{dot} is synthesized from L-arginine by an NO-synthase (NOS) as in other animals. The beewolf NOS gene revealed no conspicuous differences to related species. However, due to alternative splicing, the NOS-mRNA in beewolf eggs lacks a 144bp exon near the regulatory domain. This preventive external application of high doses of NO{dot} by seemingly defenseless wasp eggs represents an evolutionary key innovation that adds a remarkable novel facet to the array of functions of the important biological effector NO{dot}.

ecology↗

bioRxiv2017

Ancient symbiosis confers desiccation resistance to stored grain pest beetles

Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, e.g. temperature and humidity. Here we report on an ancient (~400 Mya) clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated withgrain and wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly improving fitness under dry conditions. Together with earlier observations on symbiont contributions to cuticle biosynthesis in weevils, our findings indicate that convergent acquisitions of bacterial mutualists represented key adaptations enabling diverse pest beetle groups to survive and proliferate under the low ambient humidities that characterize dry grain storage facilities.

evolutionary biology↗