Search Results (79)

The interaction between plants and phytophagous insects is one of the most complex relationships in ecosystems. By acting as direct third-party participants, gut symbionts redefine this binary antagonistic relationship. This article reviews the roles of gut symbionts in the adaptive evolution of phytophagous insects, highlighting their important roles in degrading plant secondary metabolites, modulating plant defense responses, promoting insect nutrient absorption, and shaping immune phenotypes. Gut symbionts not only enhance the adaptability of insects by degrading plant defense compounds, but also significantly influence their physiological adaptation by manipulating plant defense signaling pathways, regulating the immune system of insects, and promoting their rapid adaptation to external stress. When insects are confronted with environmental changes or shifts of host plants, the dynamic plasticity of the gut symbionts provides them with evolutionary advantages. Reviewing the mechanism of action of intestinal symbiotic bacteria in the adaptive evolution of insects is helpful to deepen our understanding of the ecological interaction process between insects and plants. Full article

This study investigated the diversity, distribution, and seasonal abundance of ambrosia and pine bark beetles (PBBs) in the Florida Panhandle, focusing on Leon and Gadsden Counties between July 2022 and October 2023. A total of 1657 specimens representing 24 species and 18 genera were captured using baited Lindgren funnel traps. Dominant species varied by location: Xyleborinus saxesenii, Cnestus mutilatus, and Xylosandrus crassiusculus were most abundant in Leon County, while Xylosandrus amputatus prevailed in Gadsden County. Three new county records were documented, including Xylosandrus amputatus and Ambrosiodmus lewisi for Leon County, and Cyclorhipidion distinguendum for Gadsden County. Additionally, three ambrosia beetle species within Platypodinae Euplatypus compositus, Myoplatypus flavicornis, and Euplatypus compositus were recorded across both counties. Seasonal patterns showed pronounced activity peaks during spring and early fall, corresponding with warmer and more humid conditions that support beetle reproduction and host colonization. Climatic analysis revealed that moisture-related variables, particularly relative humidity and precipitation, were the strongest predictors of beetle abundance, reflecting the ecological dependence of ambrosia beetles on fungal symbionts. Greater species richness observed in Leon County suggests that favorable microclimatic and habitat conditions enhance colonization dynamics. The documentation of new county records highlights the influence of shifting trade pathways, human movement, and environmental change on species introductions. The findings underscore the need for continuous surveillance and refined detection systems integrating ethanol-based lures and species-specific pheromones. As climate change continues to modify forest ecosystems, these results provide essential guidance for developing proactive monitoring and management strategies to protect forest health, biodiversity, and timber resources in the Florida Panhandle. Full article

Deep-sea mussels of the genus Bathymodiolus exhibit adaptability to nutrient-poor deep-sea environments by establishing nutritional intracellular symbiosis with chemosynthetic bacteria harbored within the gill epithelial cells. However, this poses a conflict for the innate immune system of the host, which must balance the tolerance of beneficial symbiotic bacteria with the need to eliminate exogenous microbes. This review synthesizes existing knowledge and recent findings on Bathymodiolus japonicus to outline the cellular and molecular mechanisms governing this symbiotic relationship. In the host immune system, hemocytes are responsible for systemic defense, whereas gill cells are involved in local symbiotic acceptance. Central to the establishment of symbiosis is the host’s phagocytic system, which non-selectively engulfs bacteria but selectively retains symbionts. We highlight a series of cellular events in gill cells involving the engulfment, selection, retention and/or digestion of symbionts, and the regulatory mechanism of phagocytosis through mechanistic target of rapamycin complex 1, which connects bacterial nutrient supply with host immune and metabolic responses. This integrated model of symbiosis regulation, which links immunity, metabolism, and symbiosis, provides a fundamental framework for understanding how hosts establish and maintain a stable coexistence with microbes, offering a new perspective on symbiotic strategies in diverse organisms. Full article

Arbuscular mycorrhizal (AM) fungi establish mutualistic symbioses with plant roots, enhancing plant growth and improving soil fertility through nutrient exchange. Among these, soil nitrogen (N) and phosphorus (P) are critical for symbiosis formation, directly influencing nutrient uptake and translocation within the symbiotic system. This study aimed to examine the regulatory roles of N and P levels on AM fungal development and associated bacterial communities in culture. Sorghum was used as the host plant in pot experiments with two AM fungi, Rhizophagus irregularis and Funneliformis mosseae, under varying N and P concentrations. The analyzed parameters included mycorrhizal colonization, propagule production, plant biomass, nutrient contents (N, P, and K), and bacterial community diversity. N3P1 treatment (150 mg/L N, 30 mg/L P) yielded the highest colonization rate, spore production, and arbuscule abundance in both AM fungal symbionts. At equivalent N and P concentrations, the N, P, and K contents in inoculated plants were significantly higher than those in controls. AM fungal inoculation markedly increased the bacterial diversity in the culture (Shannon index raised by 15.2–28.7%) and enriched beneficial taxa, such as Bradyrhizobium and Pseudomonas. N and P concentrations substantially influenced AM fungal symbiosis, with optimal development observed under N3P1 conditions. By regulating AM symbiotic establishment, N and P levels reshaped microbial community composition, providing theoretical guidance for industrialized AM fungal cultivation and inoculant production. Full article

Aphids remain exceptional models for symbiosis research due to their unique experimental advantages that extend beyond documenting symbiont-mediated phenotypes. Nine commonly occurring facultative bacterial symbionts provide well-characterized benefits, including defense against parasitoids, pathogens, and thermal stress. Yet the system’s greatest value lies in enabling diverse research applications across biological disciplines through experimental tractability combined with ecological realism. Researchers can create controlled experimental lines through symbiont manipulation, maintain clonal host populations indefinitely, and cultivate symbionts independently. This experimental power is complemented by extensive knowledge of symbiont dynamics in natural populations, including temporal and geographic distribution patterns—features generally unavailable in other insect-microbe systems. These advantages facilitate investigation of key processes in symbiosis, including transmission dynamics, mechanisms, strain-level functional diversity, multi-partner infections, and transitions from facultative to co-obligate relationships. Integration across biological scales—from genomics to field ecology—enables research on symbiont community assembly, ecological networks, coevolutionary arms races, and agricultural applications. This combination of experimental flexibility, comprehensive natural history knowledge, and applied relevance positions aphids as invaluable for advancing symbiosis theory while addressing practical challenges in agriculture and invasion biology. Full article

Insect pests impose major economic, agricultural, and public health burdens, damaging crops and transmitting pathogens such as dengue, malaria, and Zika. Conventional chemical control is increasingly ineffective due to insecticide resistance and environmental concerns, prompting a search for innovative strategies. The insect microbiome—comprising both obligate symbionts and environmentally acquired microbes—emerges as a key driver of host physiology and behavior. Microbes influence nutrient acquisition, immunity, reproduction, and chemosensory processing, often to promote their own transmission. By modulating olfactory and gustatory pathways, microbiota can alter host-seeking, mate choice, foraging, and oviposition patterns, reshaping ecological interactions and vector dynamics. These effects are shaped by microbial acquisition routes, habitat conditions, and anthropogenic pressures such as pesticide use, pollution, and climate change. Understanding these multi-directional interactions offers opportunities to design highly specific, microbe-based insect control strategies, from deploying microbial metabolites that disrupt host sensory systems to restoring beneficial symbionts in threatened pollinators. Integrating microbiome ecology with insect physiology and behavior not only deepens our understanding of host–microbe coevolution but also enables the development of sustainable, targeted alternatives to chemical insecticides. This review synthesizes current evidence linking microbiomes to insect biology and explores their potential as tools for pest and vector management. Full article

Dysbiosis is a strategy to control insect pests through disrupting symbiotic bacteria essential for their life cycle. The olive fly, Bactrocera oleae, has been considered a suitable system for dysbiosis, as the insect is strictly dependent on its unique symbiont Candidatus Erwinia dacicola. Here, we review older and recent results from studies of the interaction of the symbiont and its host fly. We then discuss possible methods for disrupting the symbiosis as a means to control the fly. Specifically, we summarize studies using microscopy methods that have investigated in great detail the organs where the bacterium resides and it is always extracellular. Furthermore, we discuss how genome sequences of both host and bacterium can provide valuable resources for understanding the interaction and transcriptomic analyses that have revealed important insights that can be exploited for dysbiosis strategies. We also assess experiments where compounds have been tested against the symbiont. The hitherto limited efficacy in decreasing bacterial abundance suggests that novel molecules and/or new ways for the delivery of agents will be important for successful dysbiosis strategies. Finally, we discuss how gene drive methods could be implemented in olive fly control, though a number of hurdles would need to be overcome. Full article

Recent advances in microbiome studies have deepened our understanding of endosymbionts and gut-associated microbiota in host biology. Of those, lepidopteran systems in particular harbor a complex and diverse microbiome with various microbial taxa that are stable and transmitted between larval and adult stages, and others that are transient and context-dependent. We highlight key microorganisms—including Bacillus, Lactobacillus, Escherichia coli, Pseudomonas, Rhizobium, Fusarium, Aspergillus, Saccharomyces, Bifidobacterium, and Wolbachia—that play critical roles in microbial ecology, biotechnology, and microbiome studies. The fitness implications of these microbial communities can be variable; some microbes improve host performance, while others neither positively nor negatively impact host fitness, or their impact is undetectable. This review examines the central position played by the gut microbiota in interactions of insects with plants, highlighting the functions of the microbiota in the manipulation of the behavior of herbivorous pests, modulating plant physiology, and regulating higher trophic levels in natural food webs. It also bridges microbiome ecology and applied pest management, emphasizing S. frugiperda as a model for symbiont-based intervention. As gut microbiota are central to the life history of herbivorous pests, we consider how these interactions can be exploited to drive the development of new, environmentally sound biocontrol strategies. Novel biotechnological strategies, including symbiont-based RNA interference (RNAi) and paratransgenesis, represent promising but still immature technologies with major obstacles to overcome in their practical application. However, microbiota-mediated pest control is an attractive strategy to move towards sustainable agriculture. Significantly, the gut microbiota of S. frugiperda is essential for S. frugiperda to adapt to a wide spectrum of host plants and different ecological niches. Studies have revealed that the microbiome of S. frugiperda has a close positive relationship with the fitness and susceptibility to entomopathogenic fungi; therefore, targeting the S. frugiperda microbiome may have good potential for innovative biocontrol strategies in the future. Full article

The cotton aphid, Aphis gossypii, is a globally significant agricultural pest whose microbiota plays vital roles in its physiology and adaptation. However, the dynamics of bacterial communities across its developmental stages remain poorly understood. This study employed full-length 16S rRNA gene sequencing to characterize the microbiota structure, diversity, and functional potential in nine developmental stages of A. gossypii, including egg, nymph (1-, 3-, 5-, 7-day-old), and adult (1-, 3-, 5-, 7-day-old). Results revealed Proteobacteria (72.75–95.51%) as the dominant phylum across all stages, with Buchnera aphidicola (primary obligate symbiont) constituting over 23.83% of bacterial abundance and peaking in eggs (≈80%). Alpha diversity indices (Shannon, Simpson) indicated significantly higher microbial diversity in nymphs compared to adults, suggesting stage-specific ecological interactions. While beta diversity analysis showed no structural clustering by developmental stage, functional predictions highlighted enrichment in metabolic pathways (>73% of genes), though limitations in 16S-based functional inference were noted. Notably, facultative symbionts like Hamiltonella or Serratia were absent, contrasting with other aphid systems. Dynamic shifts in Buchnera titer and the prominence of Delftia tsuruhatensis and Enterobacter hormaechei implied potential roles in host adaptation. These findings highlight the persistent dominance of the obligate symbiont Buchnera aphidicola across all developmental stages, despite quantitative fluctuations in its abundance, alongside stage-specific shifts in facultative bacterial communities, offering insights into novel targets for microbiome-driven pest management strategies. Further multi-omics approaches are warranted to validate functional contributions of these microbial communities. Full article

Epichloë endophytic fungi are important microbial resources in agriculture and animal husbandry. Because of their stable symbiosis, species transmission, and positive effects on host plants, the use of endophytic fungi in grass breeding is of great significance. In this study, six inoculation methods were used, including the sterile seedling slit inoculation method, sterile seedling cut inoculation method, sterile seedling injection inoculation method, seed soaking inoculation method, seed piercing and then soaking inoculation method, and seed slit inoculation method. Spectrometry was used to construct new symbionts, and Liquid Chromatography–mass spectrometry was used to analyze the effects of endophytic fungi on the metabolism of new hosts. The physiological response of the new symbionts to salt and alkali stress was studied using a pot experiment. The results were as follows: In this study, Epichloë bromicola was successfully inoculated into Bromus inermis via the sterile seedling slit inoculation method, and new symbionts (EI) were obtained; the vaccination rate was 2.1%. Metabolites up-regulated by EI are significantly enriched in citrate cycle and ascorbate and aldarate metabolism, suggesting that the symbiosis of endophytic fungi indirectly triggers the production of reactive oxygen species (ROS) through multiple metabolic pathways. The saline–alkali stress test showed that the host antioxidant system was active after inoculation, and the total antioxidant capacity was significantly increased compared with non-symbionts (EF) under mild stress (p < 0.05), which provided important clues to reveal the complex mechanism of plant–fungus symbiosis. This study provides practical guidance and a theoretical basis for plant adaptation under climate change, health management of grass seeds, and soil improvement through endophytic fungi. Full article

Termites are eusocial insects with functionally specialized workers and soldiers, both sharing the same genotype. Additionally, lower termites host flagellates in their hindguts that assist in wood digestion. However, worker-biased and soldier-biased gene expression patterns of the host–flagellate symbiotic system remain underexplored in most taxonomic groups. In this study, we sequenced high-depth transcriptomes from the workers and soldiers of a lower termite, Neotermes binovatus (Kalotermitidae), to investigate the differentially expressed termite transcripts, flagellate transcript abundance, and co-expression patterns of the host–flagellate transcript pairs in both castes. The worker-biased transcripts were enriched in functions related to cuticle development, nervous system regulation, pheromone biosynthesis, and metabolism, whereas the soldier-biased transcripts were predominantly involved in muscle development and kinesis, body morphogenesis, protein modification, and aggression. Flagellate transcripts from the orders Cristamonadida, Trichomonadida, Tritrichomonadida, and Oxymonadida were identified in both workers and soldiers, with the abundance of most flagellate transcripts tending to be higher in workers than in soldiers. Furthermore, we observed a much larger number of strong co-expression correlations between the termite and flagellate transcripts in workers than in soldiers, suggesting the possibility that soldiers depend more on food processed by worker holobionts than on their own symbiotic system. This research provides insights into the functional specialization of the host–flagellate symbiotic system in the worker and soldier castes of termites, supporting the workers’ roles in nest maintenance, preliminary food processing, and communication, while emphasizing the defensive role of soldiers. Additionally, it offers new perspectives on the potential termite-flagellate interactions and underscores the need for whole-genome data of termite flagellates in further studies. Full article

Numerous organisms, including animals, plants, fungi, protists, and bacteria, rely on toxins to meet their needs. Biological toxins have been classified into three groups: poisons transferred passively without a delivery mechanism; toxungens delivered to the body surface without an accompanying wound; and venoms conveyed to internal tissues via the creation of a wound. The distinctions highlight the evolutionary pathways by which toxins acquire specialized functions. Heretofore, the term venom has been largely restricted to animals. However, careful consideration reveals a surprising diversity of organisms that deploy toxic secretions via strategies remarkably analogous to those of venomous animals. Numerous plants inject toxins and pathogenic microorganisms into animals through stinging trichomes, thorns, spines, prickles, raphides, and silica needles. Some plants protect themselves via ants as venomous symbionts. Certain fungi deliver toxins via hyphae into infected hosts for nutritional and/or defensive purposes. Fungi can possess penetration structures, sometimes independent of the hyphae, that create a wound to facilitate toxin delivery. Some protists discharge harpoon-like extrusomes (toxicysts and nematocysts) that penetrate their prey and deliver toxins. Many bacteria possess secretion systems or contractile injection systems that can introduce toxins into targets via wounds. Viruses, though not “true” organisms according to many, include a group (the bacteriophages) which can inject nucleic acids and virion proteins into host cells that inflict damage rivaling that of conventional venoms. Collectively, these examples suggest that venom delivery systems—and even toxungen delivery systems, which we briefly address—are much more widespread than previously recognized. Thus, our understanding of venom as an evolutionary novelty has focused on only a small proportion of venomous organisms. With regard to this widespread form of toxin deployment, the words of the Sherman Brothers in Disney’s iconic tune, It’s a Small World, could hardly be more apt: “There’s so much that we share, that it’s time we’re aware, it’s a small world after all”. Full article

Paramecium bursaria, a ciliated protist, forms a symbiotic relationship with the green alga Chlorella variabilis. This endosymbiotic association is a model system for studying the establishment of secondary symbiosis and interactions between the symbiont and its host organisms. Symbiotic algae reside in specialized compartments called perialgal vacuoles (PVs) within the host cytoplasm, which protect them from digestion by host lysosomal fusion. The relationship between P. bursaria and symbiotic Chlorella spp. is characterized by mutualism, in which both organisms benefit from this association. Furthermore, symbiotic algae also influence their host phenotypes, and algae-free P. bursaria can be obtained through various methods and reassociated with symbiotic algae, making it a valuable tool for studying secondary endosymbiosis. Recent advancements in genomic and transcriptomic studies on both hosts and symbionts have further enhanced the utility of this model system. This review summarizes the infection process of the symbiotic alga C. variabilis and its effects on the algal infection on number of host trichocysts, mitochondria, cytoplasmic crystals, total protein amount, stress responses, photoaccumulation, and circadian rhythms of the host P. bursaria. Full article

Burkholderia (sensu lato) is a diverse group of β-Proteobacteria that exists worldwide in various environments. The SBE clade of this group was thought to be mutualistic with stinkbugs. Riptortus–Burkholderia was suggested as an ideal model system for studying insect–microbe symbiosis. To explore the strain-level diversity of Burkholderia at the individual and population levels of Riptortus stinkbugs (Hemiptera: Alydidae), and to uncover the factors affecting the Burkholderia community, large-scale sampling of two Riptortus species and deep sequencing data (16S amplicon) were used in the present study. Our results showed that: (1) the proportions of facultative symbiotic bacteria Burkholderia were very high, with an average proportion of 87.1% in the samples; (2) only six out of 1373 Burkholderia amplicon sequence variants (ASVs) did not belong to the SBE clade, accounting for only 0.03% of Burkholderia; (3) a relatively small number of Burkholderia ASVs had a large number of sequences, with 22, 54, and 107 ASVs accounting for more than 1.0%, 0.1%, and 0.01% of the total Burkholderia sequences, respectively; (4) multiple Burkholderia ASVs were present in most Riptortus individuals, but there was one dominant or two codominant ASVs, and codominance was more likely to occur when the genetic distance between the two codominant ASVs was small; and (5) the beta diversity of Burkholderia was significantly different between the two host species (PerMANOVA: both Jaccard and Bray–Curtis, p < 0.001) and among localities (PerMANOVA: both Jaccard and Bray–Curtis, p < 0.001). Two-way PerMANOVA also indicated that both the host (Bray–Curtis, p = 0.020; Jaccard, p = 0.001) and geographical location (Bray–Curtis, p = 0.041; Jaccard, p = 0.045) influence Burkholderia communities; furthermore, Mantel tests showed that the Burkholderia communities were significantly correlated with the geographical distance of sample locations (R = 0.056, p = 0.001). Together, our findings demonstrate the fine-scale diversity of Burkholderia symbionts and suggest a region- and host-dependent pattern of Burkholderia in Riptortus stinkbugs. Full article

Insects protect themselves through their immune systems. Entomopathogenic nematodes and their bacterial symbionts are widely used for the biocontrol of economically important pests. Ascarosides are pheromones that regulate nematode behaviors, such as aggregation, avoidance, mating, dispersal, and dauer recovery and formation. However, whether ascarosides influence the immune response of insects remains unexplored. In this study, we co-injected ascarosides and symbiotic Photorhabdus luminescens subsp. kayaii H06 bacteria derived from Heterorhabditis bacteriophora H06 into the last instar larvae of Galleria mellonella. We recorded larval mortality and analyzed the expressions of AMPs, ROS/RNS, and LPSs. Our results revealed a process in which ascarosides, acting as enhancers of the symbiotic bacteria, co-induced G. mellonella immunity by significantly increasing oxidative stress responses and secreting AMPs (gallerimycin, gloverin, and cecropin). This led to a reduction in color intensity and the symbiotic bacteria load, ultimately resulting in delayed host mortality compared to either ascarosides or symbiotic bacteria. These findings demonstrate the cross-kingdom regulation of insects and symbiotic bacteria by nematode pheromones. Furthermore, our results suggest that G. mellonella larvae may employ nematode pheromones secreted by IJs to modulate insect immunity during early infection, particularly in the presence of symbiotic bacteria, for enhancing resistance to invasive bacteria in the hemolymph. Full article