Lactobacillus plantarum promotes Drosophila systemic growth by modulating hormonal signals through TOR-dependent nutrient sensing

Nanoplastic exposure affects the intestinal microbiota of adult Drosophila flies

Micro- and nanoplastics (MNPLs) are emerging environmental pollutants that have garnered significant attention over the past few decades due to their detrimental effects on human health through various exposure pathways. This study investigates the impact of MNPLs on gut microbiota, utilizing Drosophila melanogaster as a model organism. Drosophila was selected for its microbiota's similarities to humans and its established role as an accessible and well-characterized model system. To analyze microbiota, full-length 16S rRNA gene sequencing was performed using the Nanopore sequencing platform, enabling comprehensive profiling of the microbial populations present in the samples. As models of MNPLs, two commercial polystyrene nanoplastics (PS-NPLs, 61.20 and 415.22 nm) and one lab-made polylactic acid nanoplastic (PLA-NPLs, 463.90 nm) were selected. As a positive control, zinc oxide nanoparticles (ZnO-NPs) were used. The observed findings revealed that exposure to MNPLs induced notable alterations in gut microbiota, including a reduction in bacterial abundance and shifts in species composition. These results suggest that MNPLs exposure can lead to microbial dysbiosis and potential gut health disruptions through its interaction, either with the gut epithelial barrier or directly with the resident microorganisms.

Attraction of Bactrocera cucurbitae (Coquillett) to selected gut microbiota supernatants: implications for pest control

BACKGROUND

Bactrocera cucurbitae (Coquillett) is a distructive quarantine insect pest that causes significant economic losses on cucurbit crops. To explore a green control approach, we investigated the behavioral responses of B. cucurbitae larvae and adults to bacterial suspensions, sediments, and supernatants derived from eight gut microbial strains across four distinct genera. The proboscis extension response was used to evaluate the impact of these microbial strains. In addition, using food selection experiments, two-choice trap methods, and gas chromatography-mass spectrometry, we isolated and identified the predominant volatile compounds in the microbiota supernatants.

RESULTS

Among the tested gut microbial strains, Kluyvera, Morganella, and Providencia exhibited notable attraction toward B. cucurbitae. In particular, the supernatant of Providencia M38 revealed the most highly attractive effect on B. cucurbitae larvae, whereas the supernatant of Morganella M72 was highly attractive to B. cucurbitae adults. Primary components present in the supernatant of M38 and M72 were dimethyl disulfide, indole, 2-nonone, phenethyl alcohol, and 1-decanol.

CONCLUSION

Strains of M38 and M72 displayed remarkable attractive properties for B. cucurbitae larvae and adults, respectively, presenting promising potential for developing a novel attractant for this pest species. © 2025 Society of Chemical Industry.

Candidatus Liberibacter asiaticus influences the emergence of the Asian citrus psyllid Diaphorina citri by regulating key cuticular proteins

The Asian citrus psyllid, Diaphorina citri, is the primary vector of the HLB pathogen, Candidatus Liberibacter asiaticus (CLas). The acquisition of CLas shortens the developmental period of nymphs, accelerating the emergence into adulthood and thereby facilitating the spread of CLas. Cuticular proteins (CPs) are involved in insect emergence. In this study, we investigated the molecular mechanisms underlying CLas-promoted emergence in D. citri via CP mediation. Here, a total of 159 CP genes were first identified in the D. citri genome. Chromosomal location analysis revealed an uneven distribution of these CP genes across the 13 D. citri chromosomes. Proteomic analysis identified 54 differentially expressed CPs during D. citri emergence, with 14 CPs exhibiting significant differential expression after CLas acquisition. Five key genes, Dc18aa-1, Dc18aa-2, DcCPR-24, DcCPR-38 and DcCPR-58, were screened from the proteome and CLas acquisition. The silencing of these 5 genes through a modified feeding method significantly reduced the emergence rate and caused various abnormal phenotypes, indicating the crucial role that these genes play in D. citri emergence. This study provides a comprehensive overview of the role of CPs in D. citri and reveals that CLas can influence the emergence process of D. citri by regulating the expression of CPs. These key CPs may serve as potential targets for future research on controlling huanglongbing (HLB) transmission.

Distinct effects of two dominant enteric bacteria on the developmental performance of spodoptera frugiperda and their association with physiological metabolism

Enteric bacteria can play an important role in the developmental performance of their insect hosts. The present study revealed that two dominant enteric bacteria, Enterococcus mundtii and Enterococcus casseliflavus, are present in the gut of Spodoptera frugiperda larvae on different host plants (maize and rice). However, the role of the two dominant bacteria in S. frugiperda remains poorly understood. To clarify the functions of E. mundtii and E. casseliflavus, the effects on the growth and development of S. frugiperda were studied by separately adding them to an artificial diet with different proportions of yeast. To elucidate the physiological metabolism underlying the differential effects of these two enteric bacteria on the developmental performance of S. frugiperda, transcriptome sequencing was conducted. The results showed that under a rich diet (with 1.85% yeast extract), E. casseliflavus significantly inhibited larval growth and prolonged the pupal stage, under a poor diet (without yeast extract), larval survival rates decreased, but larval body weight increased, and pupal weight significantly increased. However, E. mundtii had no significant effect on S. frugiperda fed a nutritionally rich diet or poor diet. These results indicate that E. casseliflavus exerts a nutrient-dependent effect on life history traits, while E. munditi has little significant impact on the developmental performance of S. frugiperda. Transcriptome sequencing analysis of differential gene expression revealed significant suppression of genes related to physiological metabolism and carbohydrate transport in E. casseliflavus. For instance, the downregulation of UDP-glycosyltransferase (UGT) and amino acid genes is closely associated with the growth and development of Spodoptera frugiperda.These findings provide deeper insights into its impact on the growth and development of S. frugiperda.

Growth of the maternal intestine during reproduction

The organs of many female animals are remodeled by reproduction. Using the mouse intestine, a striking and tractable model of organ resizing, we find that reproductive remodeling is anticipatory and distinct from diet- or microbiota-induced resizing. Reproductive remodeling involves partially irreversible elongation of the small intestine and fully reversible growth of its epithelial villi, associated with an expansion of isthmus progenitors and accelerated enterocyte migration. We identify induction of the SGLT3a transporter in a subset of enterocytes as an early reproductive hallmark. Electrophysiological and genetic interrogations indicate that SGLT3a does not sustain digestive functions or enterocyte health; rather, it detects protons and sodium to extrinsically support the expansion of adjacent Fgfbp1-positive isthmus progenitors, promoting villus growth. Our findings reveal unanticipated specificity to physiological organ remodeling. We suggest that organ- and state-specific growth programs could be leveraged to improve pregnancy outcomes or prevent maladaptive consequences of such growth.

Microbiome-emitted scents activate olfactory neuron-independent airway-gut-brain axis to promote host growth in Drosophila

While it is now accepted that the microbiome has strong impacts on animal growth promotion, the exact mechanism has remained elusive. Here we show that microbiome-emitted scents contain volatile somatotrophic factors (VSFs), which promote host growth in an olfaction-independent manner in Drosophila. We found that inhaled VSFs are readily sensed by olfactory receptor 42b non-neuronally expressed in subsets of tracheal airway cells, enteroendocrine cells, and enterocytes. Olfaction-independent sensing of VSFs activates the airway-gut-brain axis by regulating Hippo, FGF and insulin-like growth factor signaling pathways, which are required for airway branching, organ oxygenation and body growth. We found that a mutant microbiome that did not produce (2R,3R)-2,3-butanediol failed to activate the airway-gut-brain axis for host growth. Importantly, forced inhalation of (2R,3R)-2,3-butanediol completely reversed these defects. Our discovery of contact-independent and olfaction-independent airborne interactions between host and microbiome provides a novel perspective on the role of the airway-gut-brain axis in microbiome-controlled host development.

Lack of significant effect of gut microbiota on weight gain in newly emerged worker honeybee

The western honeybee, Apis mellifera, harbours a simple and distinct microbiota that has been linked to various positive outcomes for the host. Among these cited benefits is improved weight gain for bees that have been inoculated with their native microbes. This result has been challenged by recent studies which investigated the impact of the gut microbiota on behavioural maturation and associated physiological changes and revealed no effect of the gut microbiota on weight gain. Therefore, we re-examined the role of the microbiota in weight gain by comparing microbiota-deprived bees with those inoculated with gut homogenate or defined communities composed of isolates representing the major bacterial taxa inhabiting the bee gut. We observed no differences in weight gain of adult bees or of their gut tissues across these groups. Further analysis based on nurse/forager cuticular hydrocarbon status and bacterial composition also revealed no significant changes. These results suggest the need for more nuanced investigations aimed at exploring factors such as the conditions in the hive of origin, including larval nutrition.

Comparing the antioxidant effects of single and binary combinations of Lactiplantibacillus plantarum in vitro and in vivo and their application in yogurt

Lactiplantibacillus plantarum have been studied for their antioxidant properties, which can mitigate oxidative stress and improve health outcomes. The study aimed to compare the antioxidant properties of single and binary L. plantarum and their impact on yogurt. Lactiplantibacillus plantarum 847 (Lp-C), L. plantarum 8014 (Lp-G), and their combination were chosen for their in vitro antioxidant potential. In vivo experiments were performed in Drosophila melanogaster and results showed that binary L. plantarum notably improved the survival time, weight, catalase activity and intestinal integrity in H2O2-induced flies. As compared with single L. plantarum treated flies, binary strains improved the survival curve, superoxide dismutase and catalase activities in females, prolonged the average survival time in males, and increased the expression level of keap1, Nrf2, and SOD genes in all sexes. To explore the effect of single and binary L. plantarum on milk fermentation, the physicochemical properties and antioxidant activity of yogurt were detected, and results presented that yogurt fermented with L. plantarum exhibited the improved antioxidant capacity, with the binary strain combination demonstrating superior effects in rheological properties and the later period of yogurt storage. This research offers a foundation for choosing the combinations of lactic acid bacteria with antioxidant properties.

Commensal acidification of specific gut regions produces a protective priority effect against enteropathogenic bacterial infection

The commensal microbiome has been shown to protect against newly introduced enteric pathogens in multiple host species, a phenomenon known as a priority effect. Multiple mechanisms can contribute to this protective priority effect, including antimicrobial compounds, nutrient competition, and pH changes. In Drosophila melanogaster , Lactiplantibacillus plantarum has been shown to protect against enteric pathogens. However, the strains of L. plantarum studied were derived from laboratory flies or non-fly environments and have been found to be unstable colonizers of the fly gut that mainly reside on the food. To study the priority effect using a naturally occurring microbial relationship, we isolated a wild-fly derived strain of L. plantarum that stably colonizes the fly gut in conjunction with a common enteric pathogen, Serratia marcescens . Flies stably associated with the L. plantarum strain were more resilient to oral Serratia marcescens infection as seen by longer lifespan and lower S. marcescens load in the gut. Through in vitro experiments, we found that L. plantarum inhibits S. marcescens growth due to acidification. We used gut imaging with pH-indicator dyes to show that L. plantarum reduces the gut pH to levels that restrict S. marcescens growth in vivo . In flies colonized with L. plantarum prior to S. marcescens infection, L. plantarum and S. marcescens are spatially segregated in the gut and S. marcescens is less abundant where L. plantarum heavily colonizes, indicating that acidification of specific gut regions is a mechanism of a protective priority effect.

A Drosophila holidic diet optimized for growth and development

Diets composed of chemically pure components (holidic diets) are useful for determining the metabolic roles of individual nutrients. For the model organism Drosophila melanogaster, existing holidic diets are unable to support the rapid growth characteristic of the larval stage. Here, we use a nutrient co-optimization strategy across more than 50 diet variants to design HolFast, a holidic medium tailored to fast larval growth and development. We identify dietary amino acid ratios optimal for developmental speed but show that they compromise survival unless vitamins and sterols are co-optimized. Rapid development on HolFast is not improved by adding fatty acids, but it is dependent upon their de novo synthesis in the fat body via fatty acid synthase (FASN). HolFast outperforms other holidic diets, supporting rates of growth and development close to those of yeast-based diets and, under germ-free conditions, identical. HolFast has wide applications in nutritional and metabolic studies of Drosophila development.

The gut microbiome promotes locomotion of Drosophila larvae via octopamine signaling

The gut microbiome is a key partner of animals, influencing various aspects of their physiology and behaviors. Among the diverse behaviors regulated by the gut microbiome, locomotion is vital for survival and reproduction, although the underlying mechanisms remain unclear. Here, we reveal that the gut microbiome modulates the locomotor behavior of Drosophila larvae via a specific neuronal type in the brain. The crawling speed of germ-free (GF) larvae was significantly reduced compared to the conventionally reared larvae, while feeding and excretion behaviors were unaffected. Recolonization with Acetobacter and Lactobacillus can fully and partially rescue the locomotor defects in GF larvae, respectively, probably due to the highest abundance of Acetobacter as a symbiotic bacterium in the larval gut, followed by Lactobacillus. Moreover, the gut microbiome promoted larval locomotion, not by nutrition, but rather by enhancing the brain levels of tyrosine decarboxylase 2 (Tdc2), which is an enzyme that synthesizes octopamine (OA). Overexpression of Tdc2 rescued locomotion ability in GF larvae. These findings together demonstrate that the gut microbiome specifically modulates larval locomotor behavior through the OA signaling pathway, revealing a new mechanism underlying larval locomotion regulated by the gut microbiome.

Time-restricted feeding mediated modulation of microbiota leads to changes in muscle physiology in Drosophila obesity models

Recent research has highlighted the essential role of the microbiome in maintaining skeletal muscle physiology. The microbiota influences muscle health by regulating lipid metabolism, protein synthesis, and insulin sensitivity. However, metabolic disturbances such as obesity can lead to dysbiosis, impairing muscle function. Time-restricted feeding (TRF) has been shown to mitigate obesity-related muscle dysfunction, but its effects on restoring healthy microbiomes remain poorly understood. This study utilizes 16S microbiome analysis and bacterial supplementation to investigate the bacterial communities influenced by TRF that may benefit skeletal muscle physiology. In wild-type and obese Drosophila models (axenic models devoid of natural microbial communities), the absence of microbiota influence muscle performance and metabolism differently. Specifically, axenic wild-type Drosophila exhibited reduced muscle performance, higher glucose levels, insulin resistance, ectopic lipid accumulation, and decreased ATP levels. Interestingly, in obese Drosophila (induced by a high-fat diet or predisposed obesity mutant Sk2), the absence of microbiota improved muscle performance, lowered glucose levels, reduced insulin resistance, and increased ATP levels. TRF was found to modulate microbiota composition, notably increasing Acetobacter pasteurianus (AP) and decreasing Staphylococcus aureus (SA) in both obesity models. Supplementation with AP improved muscle performance and reduced glucose and insulin resistance, while SA supplementation had the opposite effect. This study provides novel insights into the complex interactions between TRF, microbiota, and skeletal muscle physiology in different Drosophila models.

Deciphering the Microbiota of Edible Insects Sold by Street Vendors in Thailand Using Metataxonomic Analysis

The aim of the present study was to investigate the microbiota of processed ready-to-eat (fried or boiled) edible insects sold by street vendors at local green markets in Thailand (Bangkok and Koh Samui). To this end, samples of 4 insect species (rhino beetle adults, silkworm pupae, giant waterbugs adults, and black scorpions) were collected and analyzed through viable counting and metataxonomic analysis. Enterobacteriaceae showed counts below 1 log cfu g-1 in all samples, except for black scorpions, which showed elevated counts reaching up to 4 log cfu g-1. Total mesophilic aerobes counts were up to 8 log cfu g-1 in all the analyzed samples. Counts below 1 log cfu g-1 were observed for Escherichia coli, Staphylococcus aureus, sulfite-reducing clostridia viable cells and spores, and Bacillus cereus. All the samples showed the absence of Listeria monocytogenes and Salmonella spp. According to metataxonomic analysis, 14 taxa were consistently present across all insect samples, including Dellaglioa algida, Latilactobacillus curvatus, Latilactobacillus sakei, Acetobacteraceae, Apilactobacillus kunkeei, Bombilactobacillus spp., Enterobacteriaceae, Gilliamella spp., Lactobacillus spp., Lactobacillus apis, Streptococcus thermophilus, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, and Weissella spp. Minority taxa included Alcaligenes spp., Brochothrix thermosphacta, Psychrobacter spp., Staphylococcus saprophyticus, Lactobacillus melliventris, Pediococcus spp., Levilactobacillus brevis, and Snodgrassella alvi.

Is Drosophila Larval Competition Involved in Incipient Speciation?

Geographical, ethological, temporal and ecological barriers can affect interbreeding between populations deriving from an ancestral population, this progressively leading to speciation. A rare case of incipient speciation currently occurs between Drosophila melanogaster populations sampled in Zimbabwe (Z) and all other populations (M). This phenomenon was initially characterized by Z females refusing to mate with M males. Despite the fact that Z and M flies produce different amounts of cuticular pheromones, their manipulation and that of other sensory signals exchanged during courtship behavior only marginally rescued the behavioral isolation. To further explore the putative mechanisms involved in this phenomenon, we first assessed the fecundity in matings between Z and M flies. Then, we measured the reproduction and survival in adults resulting of co-cultured Z and M larvae. In these two experiments, Z flies rarely emerged. Z and M larvae produced different amounts of food-derived metabolites which were altered in co-culture condition. This maybe related to the different bacteria composition in the gut and body of Z and M flies. However, the mating behavior of co-cultured flies did not change and their cuticular pheromone profile was slightly altered. Thus, the Z/M larval competition could reinforce the barriers induced by gametic and behavioral isolation processes on this incipient speciation phenomenon.

Protective effects of Lactobacillus plantarum strain against protein malnutrition-induced muscle atrophy and bone loss in juvenile mice

Early-life malnutrition adversely affects nearly all organ systems, resulting in multiple physiological adaptations, including growth restriction and muscle and bone loss. Although there is growing evidence that probiotics effectively improve systemic growth under malnourished conditions in different animal models, our knowledge of the beneficial effects of probiotics on various organs is limited. Here, we show that Lactobacillus plantarum strain WJL (LpWJL) can mitigate skeletal muscle and bone loss in protein-malnourished juvenile mice. Mice on prenatal day 21 were fed a protein-malnourished (P-MAL) diet with or without LpWJL supplementation for six weeks. Compared to mice on the P-MAL diet alone, LpWJL supplementation significantly increased muscle mass and size, resulting in enhanced muscle strength and endurance capacity. Furthermore, LpWJL supplementation induced the expression of the key growth factor IGF-1 while decreasing muscle atrophy markers such as Atrogin-1 and MuRF-1, indicating potential mechanisms by which protein malnutrition-induced muscle wasting is counteracted. Additionally, LpWJL supplementation alleviated the reduction in cortical bone thickness and the deterioration of trabecular bone microstructure in the femur. Taken together, these results indicate that LpWJL can protect against skeletal muscle atrophy and compromised bone microarchitecture caused by protein malnutrition, providing novel insights into the potential therapeutic applications of probiotics for treating malnutrition-related disorders.

Microbiome transplants may not improve health and longevity in Drosophila melanogaster

The gut microbiome, which is composed of bacteria, viruses, and fungi, and is involved in multiple essential physiological processes, changes measurably as a person ages, and can be associated with negative health outcomes. Microbiome transplants have been proposed as a method to improve gut function and reduce or reverse multiple disorders, including age-related diseases. Here, we take advantage of the laboratory model organism, Drosophila melanogaster, to test the effects of transplanting the microbiome of a young fly into middle-aged flies, across multiple genetic backgrounds and both sexes, to test whether age-related lifespan could be increased, and late-life physical health declines mitigated. Our results suggest that, overall, microbiome transplants do not improve longevity and may even be detrimental in flies, and the health effects of microbiome transplants were minor, but sex- and genotype-dependent. This discovery supports previous evidence that axenic flies, those with no gut microbiome, live healthier and longer lives than their non-axenic counterparts. The results of this study suggest that, at least for fruit flies, microbiome transplants may not be a viable intervention to improve health and longevity, though more research is still warranted.

Isolation and identification of Lactobacillus species from gut microbiota of Aegiale hesperiaris (Lepidoptera: Hesperiidae) larvae

Entomophagy, the practice of consuming insects, is a global tradition. In Mexico, one of the most notable and widely consumed insects is the larva of Aegiale hesperiaris. This insect feeds on the leaves of various Agave species with high polysaccharide content, suggesting their potential role as prebiotics for the intestinal microbiota, particularly lactic acid bacteria (LAB). LAB are recognized for their use as probiotics in foods due to their health-promoting capabilities. In this study, LAB from the intestinal microbiota of A. hesperiaris larvae were isolated and characterized, utilizing 16S rRNA gene identification. The analysis revealed three bacterial species from the Lactobacillaceae family, indicating a close symbiotic relationship with the insect. This suggests a significant impact on carbohydrate and protein metabolism, vitamin synthesis, and amino acid production, contributing to the high nutritional value of this edible insect. The study provides insights into the bacteria within the digestive tract of A. hesperiaris larvae and their role in enhancing the nutritional value of this edible insect. Additionally, it establishes a foundation for future research on the ecological roles and potential biotechnological benefits of these bacteria in the food industry and the development of therapies for various conditions and diseases.

The circadian clock gene period regulates the composition and daily bacterial load of the gut microbiome in Drosophila melanogaster

While Drosophila melanogaster serves as a crucial model for investigating both the circadian clock and gut microbiome, our understanding of their relationship in this organism is still limited. Recent analyses suggested that the Drosophila gut microbiome modulates the host circadian transcriptome to minimize rapid oscillations in response to changing environments. Here, we examined the composition and abundance of the gut microbiota in wild-type and arrhythmic per01 flies, under 12 h:12 h light: dark (12:12 LD) and constant darkness (DD) conditions. The gut microbiota of wild-type and per01 flies showed differences in composition, suggesting that the D. melanogaster circadian gene per has a role in shaping the gut microbiome. In 12:12 LD and DD conditions, per01 mutants showed significant daily variations in gut bacterial quantity, unlike wild-type flies. This suggests that per is involved in maintaining the daily stability of gut microbiome load in D. melanogaster. Expanding these analyses to other fly strains with disrupted circadian clocks will clarify whether these effects originate from a circadian function of per or from its possible pleiotropic effects. Finally, some gut bacteria exhibited significant 24 h fluctuations in their relative abundance, which appeared independent from the fly circadian clock, suggesting that certain gut commensal bacteria in Drosophila may possess a host-independent circadian clock.

Insects and microbes: best friends from the nursery

Insects host microbes and interact with them throughout their life cycle. This microbiota is an important, if not essential, partner participating in many aspects of insect physiology. Recent omics studies have contributed to considerable advances in the current understanding of the molecular implications of microbiota during insect development. In this review, we present an overview of the current knowledge about the mechanisms underlying interactions between developing insects and their microbial companions. The microbiota is implicated in nutrition, both via compensating for metabolic pathways lacking in the host and via regulating host metabolism. Furthermore, the microbiota plays a protective role, enhancing the insect's tolerance to, or resistance against, various environmental stresses.

Dietary Lipids and Their Metabolism in the Midgut

Animals use dietary lipids to sustain their growth and survival. Insects can synthesize fatty acids (FAs) and are autotroph for a number of lipids, but auxotroph for specific lipids classes (e.g. sterols, polyunsaturated FAs). Once ingested, lipids are hydrolysed in the intestinal lumen and taken up into intestinal cells within specific regions of the insect digestive tract. These lipids can be either stored in the intestinal cells or exported through the haemolymph circulation to specific organs. In this chapter, we describe the various lipids provided by insect diets, their extracellular hydrolysis in the gut lumen and their intake and metabolic fate in the intestinal cells. This chapter emphasizes the critical role of the digestive tract and its regionalization in processing dietary lipids prior to their transfer to the requiring tissues.

Insect Lipid Metabolism in the Presence of Symbiotic and Pathogenic Viruses and Bacteria

Insects, like most animals, have intimate interactions with microorganisms that can influence the insect host's lipid metabolism. In this chapter, we describe what is known so far about the role prokaryotic microorganisms play in insect lipid metabolism. We start exploring microbe-insect lipid interactions focusing on endosymbionts, and more specifically the gut microbiota that has been predominantly studied in Drosophila melanogaster. We then move on to an overview of the work done on the common and well-studied endosymbiont Wolbachia pipientis, also in interaction with other microbes. Taking a slightly different angle, we then look at the effect of human pathogens, including dengue and other viruses, on the lipids of mosquito vectors. We extend the work on human pathogens and include interactions with the endosymbiont Wolbachia that was identified as a natural tool to reduce the spread of mosquito-borne diseases. Research on lipid metabolism of plant disease vectors is up and coming and we end this chapter by highlighting current knowledge in that field.

Chemical genetic approaches to dissect microbiota mechanisms in health and disease

Advances in genomics, proteomics, and metabolomics have revealed associations between specific microbiota species in health and disease. However, the precise mechanism(s) of action for many microbiota species and molecules have not been fully elucidated, limiting the development of microbiota-based diagnostics and therapeutics. In this Review, we highlight innovative chemical and genetic approaches that are enabling the dissection of microbiota mechanisms and providing causation in health and disease. Although specific microbiota molecules and mechanisms have begun to emerge, new approaches are still needed to go beyond phenotypic associations and translate microbiota discoveries into actionable targets and therapeutic leads to prevent and treat diseases.

Mechanisms of Insulin Signaling as a Potential Therapeutic Method in Intestinal Diseases

Gastrointestinal diseases are becoming a growing public health problem. One of them is inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). The incidence of IBD is increasing in developing countries and declining in developed countries, affecting people of all ages. Researchers have been exploring new treatment options including insulin signaling pathways in the inflammation of the gastrointestinal tract. It seems that a better understanding of the mechanism of IGF-1, GLP-1 and TL1A on the gut microbiota and inflammation may provide new advances in future therapeutic strategies for patients with IBD, but also other intestinal diseases. This review aims to synthesize insights into the effects of GLP, IGF and anti-TL1A on inflammation and the gut microbiota, which may enable their future use in therapy for people with intestinal diseases.

Intestinal commensal bacteria promote Bactrocera dorsalis larval development through the vitamin B6 synthesis pathway

BACKGROUND

The gut microbiota can facilitate host growth under nutrient-constrained conditions. However, whether this effect is limited to certain bacterial species remains largely unclear, and the relevant underlying mechanisms remain to be thoroughly investigated.

RESULTS

We found that the microbiota was required for Bactrocera dorsalis larval growth under poor dietary conditions. Monoassociation experiments revealed that Enterobacteriaceae and some Lactobacilli promoted larval growth. Among the 27 bacterial strains tested, 14 significantly promoted larval development, and the Enterobacteriaceae cloacae isolate exhibited the most obvious promoting effect. A bacterial genome-wide association study (GWAS) revealed that the vitamin B6 synthesis pathway was critical for the promotion of E. cloacae growth. Deletion of pdxA, which is responsible for vitamin B6 biosynthesis, deprived the mutant strains of larval growth-promoting function, indicating that the 4-hydroxythreonine-4-phosphate dehydrogenase(pdxA) gene was crucial for promoting larval growth in E. cloacae. Importantly, supplementation of a poor diet with vitamin B6 successfully rescued the axenic larval growth phenotype of B. dorsalis.

CONCLUSION

Our results suggest that gut microbes promote insect larval growth by providing vitamin B6 under nutrient scarcity conditions in B. dorsalis. Video Abstract.

Bioinspired core-shell microparticle for dual-delivery of prebiotic and probiotic for the treatment of ulcerative colitis

Lactiplantibacillus plantarum (LP) is a well-known probiotic strain that has a beneficial effect in preventing ulcerative colitis. However, delivering a sufficient number of viable LP to the colon still face challenges due to its vulnerability to the highly complex intestinal flora ecosystem. Herein, we present a centrifuge-driven micronozzle system designed for double-layered core-shell alginate microcapsules (DAM), which can serve as an effective carrier for dual delivery of resistant starch nanoparticles (RSNP, prebiotic) and LP (probiotics) for the treatment of colitis. This system enables precise loading of LP and RSNP within the core and shell regions of DAM, respectively. The resulting LP/RS@DAM exhibited a high encapsulation efficiency of LP (108 CFU per bead), in which the dense distribution of RSNP in the shell effectively protected LP against acidic conditions (pH 2) and maintained the cell viability up to 52 % even after long-term storage for 30 days. Furthermore, LP/RS@DAM effectively enhances the production of short-chain fatty acids, leading to a reduction in inflammatory cytokines and restoration of intestinal microbial diversity in dextran sulfate sodium (DSS)-induced colitis. We believe that this innovative approach would offer a potential solution for improving colitis management and paving the way for tailored therapeutic interventions in gastrointestinal disorders.

Current progress on the microbial therapies for acute liver failure

Acute liver failure (ALF), associated with a clinical fatality rate exceeding 80%, is characterized by severe liver damage resulting from various factors in the absence of pre-existing liver disease. The role of microbiota in the progression of diverse liver diseases, including ALF, has been increasingly recognized, with the interactions between the microbiota and the host significantly influencing both disease onset and progression. Despite growing interest in the microbiological aspects of ALF, comprehensive reviews remain limited. This review critically examines the mechanisms and efficacy of microbiota-based treatments for ALF, focusing on their role in prevention, treatment, and prognosis over the past decade.

Environment and diet shape the geography-specific Drosophila melanogaster microbiota composition

Geographic and environmental variation in the animal microbiota can be directly linked to the evolution and wild fitness of their hosts but often appears to be disordered. Here, we sought to better understand patterns that underlie wild variation in the microbiota composition of Drosophila melanogaster . First, environmental temperature predicted geographic variation in fly microbial communities better than latitude did. The microbiota also differed between wild flies and their diets, supporting previous conclusions that the fly microbiota is not merely a reflection of diet. Flies feeding on different diets varied significantly in their microbiota composition, and flies sampled from individual apples were exceptionally depauperate for the Lactic Acid Bacteria (LAB), a major bacterial group in wild and laboratory flies. However, flies bore significantly more LAB when sampled from other fruits or compost piles. Follow-up analyses revealed that LAB abundance in the flies uniquely responds to fruit decomposition, whereas other microbiota members better indicate temporal seasonal progression. Finally, we show that diet-dependent variation in the fly microbiota is associated with phenotypic differentiation of fly lines collected in a single orchard. These last findings link covariation between the flies' dietary history, microbiota composition, and genetic variation across relatively small (single-orchard) landscapes, reinforcing the critical role that environment-dependent variation in microbiota composition can play in local adaptation and genomic differentiation of a model animal host.

SIGNIFICANCE STATEMENT

The microbial communities of animals influence their hosts' evolution and wild fitness, but it is hard to predict and explain how the microbiota varies in wild animals. Here, we describe that the microbiota composition of wild Drosophila melanogaster can be ordered by temperature, humidity, geographic distance, diet decomposition, and diet type. We show how these determinants of microbiota variation can help explain lactic acid bacteria (LAB) abundance in the flies, including the rarity of LAB in some previous studies. Finally, we show that wild fly phenotypes segregate with the flies' diet and microbiota composition, illuminating links between the microbiota and host evolution. Together, these findings help explain how variation in microbiota compositions can shape an animal's life history.

Host-diet-microbiota interplay in intestinal nutrition and health

The intestine is populated by a complex and dynamic assortment of microbes, collectively called gut microbiota, that interact with the host and contribute to its metabolism and physiology. Diet is considered a key regulator of intestinal microbiota, as ingested nutrients interact with and shape the resident microbiota composition. Furthermore, recent studies underscore the interplay of dietary and microbiota-derived nutrients, which directly impinge on intestinal stem cells regulating their turnover to ensure a healthy gut barrier. Although advanced sequencing methodologies have allowed the characterization of the human gut microbiome, mechanistic studies assessing diet-microbiota-host interactions depend on the use of genetically tractable models, such as Drosophila melanogaster. In this review, we first discuss the similarities between the human and fly intestines and then we focus on the effects of diet and microbiota on nutrient-sensing signaling cascades controlling intestinal stem cell self-renewal and differentiation, as well as disease. Finally, we underline the use of the Drosophila model in assessing the role of microbiota in gut-related pathologies and in understanding the mechanisms that mediate different whole-body manifestations of gut dysfunction.

Live yeasts accelerate Drosophila melanogaster larval development

Insect guts house a complex community of microbes that affect host physiology, performance and behavior. Gut microbiome research has largely focused on bacteria-host symbioses and paid less attention to other taxa, such as yeasts. We found that axenic Drosophila melanogaster (reared free of microbes) develops from egg to adult more slowly (ca. 13 days) than those with a natural microbiota (ca. 11.5 days). Here, we showed that live yeasts are present and reproducing in the guts of flies and that the fast development time can be restored by inoculating larvae with a single yeast species (either Saccharomyces cerevisiae or Lachancea kluyveri). Nutritional supplements (either heat-killed yeasts, or a mix of essential vitamins and amino acids) slightly sped the development of axenic flies (to ca. 12.5 days), but not to the same extent as live yeasts. During the first two instars, this acceleration appears to result from additional macronutrient availability, but during the third instar, when most growth occurs, live yeasts increased feeding rate, implying an effect mediated by the gut-brain axis. Thus, the fly-yeast interaction extends beyond yeasts-as-food to yeasts as beneficial interactive symbionts.

Causal relationship between gut microbiota and insulin-like growth factor 1: a bidirectional two-sample Mendelian randomization study

Background

The causal relationship between gut microbiota and insulin-like growth factor 1 (IGF-1) remains unclear. The purpose of this study was to explore the causal relationship between gut microbiota and IGF-1 in men and women.

Methods

Single-nucleotide polymorphisms (SNPs) related to gut microbiota were derived from pooled statistics from large genome-wide association studies (GWASs) published by the MiBioGen consortium. Pooled data for IGF-1 were obtained from a large published GWAS. We conducted Mendelian randomization (MR) analysis, primarily using the inverse variance weighted (IVW) method. Additionally, we performed sensitivity analyses to enhance the robustness of our results, focusing on assessing heterogeneity and pleiotropy.

Results

In forward MR analysis, 11 bacterial taxa were found to have a causal effect on IGF-1 in men; 14 bacterial taxa were found to have a causal effect on IGF-1 in women (IVW, all P < 0.05). After false discovery rate (FDR) correction, all bacterial traits failed to pass the FDR correction. In reverse MR analysis, IGF-1 had a causal effect on nine bacterial taxa in men and two bacterial taxa in women respectively (IVW, all P < 0.05). After FDR correction, the causal effect of IGF-1 on order Actinomycetales (PFDR = 0.049) remains in men. The robustness of the IVW results was further confirmed after heterogeneity and pleiotropy analysis.

Conclusion

Our study demonstrates a bidirectional causal link between the gut microbiota and IGF-1, in both men and women.

The impact of carvacrol on the larval gut bacterial structure and function of Lymantria dispar

Introduction

The gut bacteria of insects play an important role in regulating their metabolism, immune system and metabolizing pesticides. Our previous results indicate that carvacrol has certain gastric toxic activity on Lymantria dispar larvae and affects their detoxification metabolism at the mRNA level. However, the impact of carvacrol on the gut bacteria of L. dispar larvae has been unclear.

Methods

In this study, the 16S rRNA sequencing technology was used to sequence and analyze the gut bacteria of the larvae which were exposed with sublethal concentration (0.297 mg/mL) and median lethal concentration (1.120 mg/mL), respectively.

Results

A total of 10 phyla, 16 classes, 47 orders, 72 families, 103 genera, and 135 species were obtained by using a 97% similarity cutoff level. The dominant bacterial phyla in the gut of the L. dispar larvae are Firmicutes and Proteobacteria. The treatment with carvacrol can significantly affect the structure of gut bacteria in the larvae of the L. dispar. At both doses, carvacrol can shift the dominant gut bacteria of the larvae from Proteobacteria to Firmicutes. At the genus level, two doses of carvacrol can significantly enhance the relative abundance of probiotic Lactobacillus in the gut of L. dispar larvae (p ≤ 0.01). Additionally, significant differences were observed among the five bacterial genera Burkholderia-Caballeronia-Paraburkholderia, Anoxybacillus, Pelomonas, Mesorhizobium (p ≤ 0.05). The analysis of α-diversity and β-diversity indicates that the treatment with carvacrol at two doses significantly affect the bacterial richness and diversity in the larvae. However, the results of functional classification prediction (PICRUSt) indicate that carvacrol significantly down-regulate 7 functions, including Energy metabolism, Cell growth and death, and up-regulate 2 functions, including Carbohydrate metabolism and Membrane transport. The network analysis indicates that the correlation between gut bacteria also has been changed. In addition, the insecticidal activity results of carvacrol against L. dispar larvae with gut bacteria elimination showed that gut bacteria can reduce the insecticidal activity of carvacrol against L. dispar larvae.

Discussion

This study provides a theoretical foundation for understanding the role of gut bacteria in detoxifying plant toxins and conferring pesticide resistance.

Microplastics in the diet of Hermetia illucens: Implications for development and midgut bacterial and fungal microbiota

In a world with a population exceeding 8 billion people and continuing to grow, pollution from food and plastic waste is causing long-term issues in ecosystems. Potential solutions may be found by exploiting insect-based bioconversion. In this context, we investigated the impact of polyvinyl chloride microparticles (PVC-MPs) on the development of Hermetia illucens (black soldier fly; BSF) and its midgut bacterial and fungal microbiota. The impact of PVC-MPs was evaluated feeding BSF larvae with a PVC-MPs-supplemented diet. The larvae exposed to different PVC-MPs concentrations (2.5%, 5%, 10% and 20% w/w) developed into adults with no significant increase in pupal mortality. Faster development and smaller pupae were observed when 20% PVC-MPs was provided. The BSF larvae ingest PVC-MPs, resulting in a reduction in MPs size. Larvae exposed to PVC-MPs did not exhibit differences in gut morphology. Regarding the impact of PVC-MPs on the structure of both bacterial and fungal communities, the overall alpha- and beta-diversity did not exhibit significant changes. However, the presence of PVC-MPs significantly affected the relative abundances of Enterobacteriaceae and Paenibacillaceae among the bacteria and of Dipodascaceae and Plectospharellaceae among the fungi (including yeast and filamentous life forms), suggesting that PVC-MP contamination has a taxa-dependent impact. These results indicate that BSF larvae can tolerate PVC-MPs in their diet, supporting the potential use of these insects in organic waste management, even in the presence of high levels of PVC-MP contamination.

Metagenomic profiling of gut microbiota in Fall Armyworm (Spodoptera frugiperda) larvae fed on different host plants

BACKGROUND

The fall armyworm (FAW, Spodoptera frugiperda) is a polyphagous pest known for causing significant crop damage. The gut microbiota plays a pivotal role in influencing the biology, physiology and adaptation of the host. However, understanding of the taxonomic composition and functional characteristics of the gut microbiota in FAW larvae fed on different host plants remains limited.

METHODS

This study utilized metagenomic sequencing to explore the structure, function and antibiotic resistance genes (ARGs) of the gut microbiota in FAW larvae transferred from an artificial diet to four distinct host plants: maize, sorghum, tomato and pepper.

RESULTS

The results demonstrated significant variations in gut microbiota structure among FAW larvae fed on different host plants. Firmicutes emerged as the dominant phylum, with Enterococcaceae as the dominant family and Enterococcus as the prominent genus. Notably, Enterococcus casseliflavus was frequently observed in the gut microbiota of FAW larvae across host plants. Metabolism pathways, particularly those related to carbohydrate and amino acid metabolism, played a crucial role in the adaptation of the FAW gut microbiota to different host plants. KEGG orthologs associated with the regulation of the peptide/nickel transport system permease protein in sorghum-fed larvae and the 6-phospho-β-glucosidase gene linked to glycolysis/gluconeogenesis as well as starch and sucrose metabolism in pepper-fed larvae were identified. Moreover, the study identified the top 20 ARGs in the gut microbiota of FAW larvae fed on different host plants, with the maize-fed group exhibiting the highest abundance of vanRC.

CONCLUSIONS

Our metagenomic sequencing study reveals significant variations in the gut microbiota composition and function of FAW larvae across diverse host plants. These findings underscore the intricate co-evolutionary relationship between hosts and their gut microbiota, suggesting that host transfer profoundly influences the gut microbiota and, consequently, the adaptability and pest management strategies for FAW.

Chitosan-coated probiotic nanoparticles mitigate acrylamide-induced toxicity in the Drosophila model

Acrylamide (ACR) with its extensive industrial applications is a classified occupational hazard toxin and carcinogenic compound. Its formation in fried potatoes, red meat and coffee during high-temperature cooking is a cause for consideration. The fabrication of chitosan-coated probiotic nanoparticles (CSP NPs) aims to enhance the bioavailability of probiotics in the gut, thereby improving their efficacy against ACR-induced toxicity in Drosophila melanogaster. Nanoencapsulation, a vital domain of the medical nanotechnology field plays a key role in targeted drug delivery, bioavailability, multi-drug load delivery systems and synergistic treatment options. Our study exploited the nanoencapsulation technology to coat Lactobacillus fermentum (probiotic) with chitosan (prebiotic), both with substantial immunomodulatory effects, to ensure the stability and sustained release of microbial load and its secondary metabolites in the gut. The combination of pre-and probiotic components, called synbiotic formulations establishes the correlation between the gut microbiota and the overall well-being of an organism. Our study aimed to develop a potent synbiotic to alleviate the impacts of heat-processed dietary toxins that significantly influence behaviour, development, and survival. Our synbiotic co-treatment with ACR in fruit flies normalised neuro-behavioural, survival, redox status, and restored ovarian mitochondrial activity, contrasting with several physiological deficits observed in the ACR-treated model.

The Future Exploring of Gut Microbiome-Immunity Interactions: From In Vivo/Vitro Models to In Silico Innovations

Investigating the complex interactions between microbiota and immunity is crucial for a fruitful understanding progress of human health and disease. This review assesses animal models, next-generation in vitro models, and in silico approaches that are used to decipher the microbiome-immunity axis, evaluating their strengths and limitations. While animal models provide a comprehensive biological context, they also raise ethical and practical concerns. Conversely, modern in vitro models reduce animal involvement but require specific costs and materials. When considering the environmental impact of these models, in silico approaches emerge as promising for resource reduction, but they require robust experimental validation and ongoing refinement. Their potential is significant, paving the way for a more sustainable and ethical future in microbiome-immunity research.

Lactobacillus Firm-5-derived succinate prevents honeybees from having diabetes-like symptoms

The gut microbiome plays an important role in honeybee hormonal regulation and growth, but the underlying mechanisms are poorly understood. Here, we showed that the depletion of gut bacteria resulted in reduced expression of insulin-like peptide gene (ilp) in the head, accompanied by metabolic syndromes resembling those of Type 1 diabetes in humans: hyperglycemia, impaired lipid storage, and decreased metabolism. These symptoms were alleviated by gut bacterial inoculation. Gut metabolite profiling revealed that succinate, produced by Lactobacillus Firm-5, played deterministic roles in activating ilp gene expression and in regulating metabolism in honeybees. Notably, we demonstrated that succinate modulates host ilp gene expression through stimulating gut gluconeogenesis, a mechanism resembling that of humans. This study presents evidence for the role of gut metabolite in modulating host metabolism and contributes to the understanding of the interactions between gut microbiome and bee hosts.

Hosts manipulate lifestyle switch and pathogenicity heterogeneity of opportunistic pathogens in the single-cell resolution

Host-microbe interactions are virtually bidirectional, but how the host affects their microbiome is poorly understood. Here, we report that the host is a critical modulator to regulate the lifestyle switch and pathogenicity heterogeneity of the opportunistic pathogens Serratia marcescens utilizing the Drosophila and bacterium model system. First, we find that Drosophila larvae efficiently outcompete S. marcescens and typically drive a bacterial switch from pathogenicity to commensalism toward the fly. Furthermore, Drosophila larvae reshape the transcriptomic and metabolic profiles of S. marcescens characterized by a lifestyle switch. More importantly, the host alters pathogenicity and heterogeneity of S. marcescens in the single-cell resolution. Finally, we find that larvae-derived AMPs are required to recapitulate the response of S. marcescens to larvae. Altogether, our findings provide an insight into the pivotal roles of the host in harnessing the life history and heterogeneity of symbiotic bacterial cells, advancing knowledge of the reciprocal relationships between the host and pathogen.

Microorganism Contribution to Mass-Reared Edible Insects: Opportunities and Challenges

The interest in edible insects' mass rearing has grown considerably in recent years, thereby highlighting the challenges of domesticating new animal species. Insects are being considered for use in the management of organic by-products from the agro-industry, synthetic by-products from the plastics industry including particular detoxification processes. The processes depend on the insect's digestive system which is based on two components: an enzymatic intrinsic cargo to the insect species and another extrinsic cargo provided by the microbial community colonizing-associated with the insect host. Advances have been made in the identification of the origin of the digestive functions observed in the midgut. It is now evident that the community of microorganisms can adapt, improve, and extend the insect's ability to digest and detoxify its food. Nevertheless, edible insect species such as Hermetia illucens and Tenebrio molitor are surprisingly autonomous, and no obligatory symbiosis with a microorganism has yet been uncovered for digestion. Conversely, the intestinal microbiota of a given species can take on different forms, which are largely influenced by the host's environment and diet. This flexibility offers the potential for the development of novel associations between insects and microorganisms, which could result in the creation of synergies that would optimize or expand value chains for agro-industrial by-products, as well as for contaminants.

Selection for stress tolerance and longevity in Drosophila melanogaster have strong impacts on microbiome profiles

There is experimental evidence that microbiomes have a strong influence on a range of host traits. Understanding the basis and importance of symbiosis between host and associated microorganisms is a rapidly developing research field, and we still lack a mechanistic understanding of ecological and genetic pressures affecting host-microbiome associations. Here Drosophila melanogaster lines from a large-scale artificial selection experiment were used to investigate whether the microbiota differ in lines selected for different stress resistance traits and longevity. Following multiple generations of artificial selection all selection regimes and corresponding controls had their microbiomes assessed. The microbiome was interrogated based on 16S rRNA sequencing. We found that the microbiome of flies from the different selection regimes differed markedly from that of the unselected control regime, and microbial diversity was consistently higher in selected relative to control regimes. Several common Drosophila bacterial species showed differentially abundance in the different selection regimes despite flies being exposed to similar environmental conditions for two generations prior to assessment. Our findings provide strong evidence for symbiosis between host and microbiomes but we cannot reveal whether the interactions are adaptive, nor whether they are caused by genetic or ecological factors.

Inter-kingdom communication and the sympoietic way of life

Organisms are now seen as holobionts, consortia of several species that interact metabolically such that they sustain and scaffold each other's existence and propagation. Sympoiesis, the development of the symbiotic relationships that form holobionts, is critical for our understanding the origins and maintenance of biodiversity. Rather than being the read-out of a single genome, development has been found to be sympoietic, based on multigenomic interactions between zygote-derived cells and symbiotic microbes. These symbiotic and sympoietic interactions are predicated on the ability of cells from different kingdoms of life (e.g., bacteria and animals) to communicate with one another and to have their chemical signals interpreted in a manner that facilitates development. Sympoiesis, the creation of an entity by the interactions of other entities, is commonly seen in embryogenesis (e.g., the creation of lenses and retinas through the interaction of brain and epidermal compartments). In holobiont sympoiesis, interactions between partners of different domains of life interact to form organs and biofilms, wherein each of these domains acts as the environment for the other. If evolution is forged by changes in development, and if symbionts are routinely involved in our development, then changes in sympoiesis can constitute an important factor in evolution.

Investigating the impact of chlorine dioxide in shrimp-rearing water on the stomach microbiome, gill transcriptome, and infection-related mortality in shrimp

AIMS

This study aimed to assess the effects of chlorine dioxide (ClO2) in water on whiteleg shrimp Penaeus vannamei, evaluating its impact on the stomach microbiota, gill transcriptome, and pathogens.

METHODS AND RESULTS

ClO2 was added to the aquarium tanks containing the shrimp. The application of ClO2 to rearing water was lethal to shrimp at concentrations above 1.2 ppm. On the other hand, most of the shrimp survived at 1.0 ppm of ClO2. Microbiome analysis showed that ClO2 administration at 1.0 ppm significantly reduced the α-diversity of bacterial community composition in the shrimp stomach, and this condition persisted for at least 7 days. Transcriptome analysis of shrimp gill revealed that ClO2 treatment caused massive change of the gene expression profile, including stress response genes. However, after 7 days of the treatment, the gene expression profile was similar to that of shrimp in the untreated control group, suggesting a recovery to the normal state. This 1.0-ppm ClO2 significantly reduced shrimp mortality in artificial challenges with an acute hepatopancreatic necrosis disease-causing Vibrio parahaemolyticus and white spot syndrome virus, which were added to rearing water.

CONCLUSIONS

The use of ClO2 at appropriate concentrations effectively eliminates a significant portion of the bacteria in the shrimp stomach and pathogens in the water. The results of this study provide fundamental knowledge on the disinfection of pathogens in water using ClO2 and the creation of semi germ-free shrimp, which has significantly decreased microbiome in the stomach.

Rickettsia symbionts spread via mixed mode transmission, increasing female fecundity and sex ratio shift by host hormone modulating

Heritable symbionts are common among animals in nature, but the molecular mechanisms underpinning symbiont invasions of host populations have been elusive. In this study, we demonstrate the spread of Rickettsia in an invasive agricultural pest, the whitefly Bemisia tabaci Mediterranean (MED), across northeastern China from 2018 to 2023. Here, we show that the beneficial symbiont Rickettsia spreads by manipulating host hormone signals. Our analyses suggest that Rickettsia have been horizontally acquired by B. tabaci MED from another invasive whitefly B. tabaci Middle East-Asia Minor 1 during periods of coexistence. Rickettsia is transmitted maternally and horizontally from female B. tabaci MED individuals. Rickettsia infection enhances fecundity and results in female bias among whiteflies. Our findings reveal that Rickettsia infection stimulates juvenile hormone (JH) synthesis, in turn enhancing fecundity, copulation events, and the female ratio of the offspring. Consequently, Rickettsia infection results in increased whitefly fecundity and female bias by modulating the JH pathway. More female progeny facilitates the transmission of Rickettsia. This study illustrates that the spread of Rickettsia among invasive whiteflies in northeastern China is propelled by host hormone regulation. Such symbiont invasions lead to rapid physiological and molecular evolution in the host, influencing the biology and ecology of an invasive species.

Comparative study of the gut microbial community structure of Spodoptera frugiperda and Spodoptera literal (Lepidoptera)

Background

Spodoptera frugiperda, the fall armyworm is a destructive invasive pest, and S. litura the tobacco cutworm, is a native species closely related to S. frugiperda. The gut microbiota plays a vital role in insect growth, development, metabolism and immune system. Research on the competition between invasive species and closely related native species has focused on differences in the adaptability of insects to the environment. Little is known about gut symbiotic microbe composition and its role in influencing competitive differences between these two insects.

Methods

We used a culture-independent approach targeting the 16S rRNA gene of gut bacteria of 5th instar larvae of S. frugiperda and S. litura. Larvae were reared continuously on maize leaves for five generations. We analyzed the composition, abundance, diversity, and metabolic function of gut microbiomes of S. frugiperda and S. litura larvae.

Results

Firmicutes, Proteobacteria, and Bacteroidetes were the dominant bacterial phyla in both species. Enterococcus, ZOR0006, Escherichia, Bacteroides, and Lactobacillus were the genera with the highest abundance in S. frugiperda. Enterococcus, Erysipelatoclostridium, ZOR0006, Enterobacter, and Bacteroides had the highest abundance in S. litura. According to α-diversity analysis, the gut bacterial diversity of S. frugiperda was significantly higher than that of S. litura. KEGG analysis showed 15 significant differences in metabolic pathways between S. frugiperda and S. litura gut bacteria, including transcription, cell growth and death, excretory system and circulatory system pathways.

Conclusion

In the same habitat, the larvae of S. frugiperda and S. litura showed significant differences in gut bacterial diversity and community composition. Regarding the composition and function of gut bacteria, the invasive species S. frugiperda may have a competitive advantage over S. litura. This study provides a foundation for developing control strategies for S. frugiperda and S. litura.

Microbiota-derived acetylcholine can promote gut motility in Drosophila melanogaster

The gut microbiota is crucial for intestinal health, including gastrointestinal (GI) motility. How commensal bacterial species influence GI motility has not been fully elucidated. A major factor of GI motility is the gut contraction promoting the propulsive movement of orally ingested materials. Here, we developed a method to monitor and quantify gut contractions in living Drosophila melanogaster larvae. We found that the culture medium of an isolated strain Lactiplantibacillus plantarum Lsi promoted gut contraction in vivo, which was not observed in Leuconostoc sp. Leui nor Acetobacter persici Ai culture medium. To identify bacteria-derived metabolites, we performed metabolome analysis of the culture media by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Of the 66 metabolites detected, we found that some metabolites changed in a species-specific manner. Among them, acetylcholine was specifically produced by L. plantarum. Feeding exogenous acetylcholine increased the frequency of gut contractions, which was blocked by D-tubocurarine, an inhibitor of nicotinic acetylcholine receptors. In this study, we propose a mechanism by which the gut microbiota influences Drosophila gut motility. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Humidity determines penetrance of a latitudinal gradient in genetic selection on the microbiota by Drosophila melanogaster

The fruit fly Drosophila melanogaster is a model for understanding how hosts and their microbial partners interact as the host adapts to wild environments. These interactions are readily interrogated because of the low taxonomic and numeric complexity of the flies' bacterial communities. Previous work has established that host genotype, the environment, diet, and interspecies microbial interactions can all influence host fitness and microbiota composition, but the specific processes and characters mediating these processes are incompletely understood. Here, we compared the variation in microbiota composition between wild-derived fly populations when flies could choose between the microorganisms in their diets and when flies were reared under environmental perturbation (different humidities). We also compared the colonization of the resident and transient microorganisms. We show that the ability to choose between microorganisms in the diet and the environmental condition of the flies can influence the relative abundance of the microbiota. There were also key differences in the abundances of the resident and transient microbiota. However, the microbiota only differed between populations when the flies were reared at humidities at or above 50% relative humidity. We also show that elevated humidity determined the penetrance of a gradient in host genetic selection on the microbiota that is associated with the latitude the flies were collected from. Finally, we show that the treatment-dependent variation in microbiota composition is associated with variation in host stress survival. Together, these findings emphasize that host genetic selection on the microbiota composition of a model animal host can be patterned with the source geography, and that such variation has the potential to influence their survival in the wild.

Importance

The fruit fly Drosophila melanogaster is a model for understanding how hosts and their microbial partners interact as hosts adapt in wild environments. Our understanding of what causes geographic variation in the fruit fly microbiota remains incomplete. Previous work has shown that the D. melanogaster microbiota has relatively low numerical and taxonomic complexity. Variation in the fly microbiota composition can be attributed to environmental characters and host genetic variation, and variation in microbiota composition can be patterned with the source location of the flies. In this work we explored three possible causes of patterned variation in microbiota composition. We show that host feeding choices, the host niche colonized by the bacteria, and a single environmental character can all contribute to variation in microbiota composition. We also show that penetrance of latitudinally-patterned host genetic selection is only observed at elevated humidities. Together, these results identify several factors that influence microbiota composition in wild fly genotypes and emphasize the interplay between environmental and host genetic factors in determining the microbiota composition of these model hosts.

Supplementation with Lactiplantibacillus brevis GKEX Combined with Resistance Exercise Training Improves Muscle Mass, Strength Performance, and Body Fat Condition in Healthy Humans

In addition to maintaining good exercise and dietary habits, recent studies have shown that probiotics may have potential benefits for muscle mass and strength. It is worth noting that the effects may vary depending on the specific strains used. To date, no studies have analyzed the effects of Lactiplantibacillus brevis in this context. Here, we combine the L. brevis strain GKEX with resistance training to further understand its effects on muscle mass, thickness, performance, and fat loss. In a six-week intervention for a double-blind randomized trial, 52 healthy subjects were divided into two groups (10 male and 16 female participants in each group): a placebo group (two capsules/day, containing 0 CFU of GKEX per capsule) and a GKEX group (two capsules/day, containing 1 × 1010 CFU of GKEX per capsule). Before the intervention, no differences were observed between the two groups in any of the tests (body composition, muscle thickness, exercise performance, and blood parameters). However, supplementation with GKEX significantly improved muscle mass and thickness, as well as grip strength, muscle strength, and explosive performance, when compared to the associated parameters before the intervention. Additionally, GKEX supplementation promoted a reduction in the body fat percentage (p < 0.05). Through analysis of the change amount, we observed that GKEX supplementation yielded significantly improved benefits when compared to the placebo group (p < 0.05). In summary, our findings support the notion that a six-week resistance exercise training program combined with L. brevis GKEX supplementation has superior additive effects that enhance muscle mass and strength performance, while also reducing body fat percentage. This intervention can promote muscle gain and fat loss.

Enterococcus casseliflavus regulates amino acid metabolism in edible insect Clanis bilineata tsingtauica: a functional metagenomics study

Introduction

The soybean hawkmoth, Clanis bilineata tsingtauica, is an edible insect that possesses high nutritional, medicinal and economic value. It has developed into a characteristic agricultural industry in China.

Methods

The dominant gut bacterium in diapause larvae of soybean hawkmoths was identified by metagenomics, and the effect of diapause time on gut microbiome composition, diversity and function was investigated.

Results

Enterococcus and Enterobacter were measured to be the dominant genera, with Enterococcus casseliflavus and Enterococcus pernyi being the dominant species. Compared to the controls, the relative abundance of E. casseliflavus and E. pernyi on day 14 was lower by 54.51 and 42.45%, respectively. However, the species richness (including the index of Chao and ACE) of gut microbiota increased on day 28 compared to controls. The gene function was mainly focused on carbohydrate and amino acid metabolism. Metabolic pathways annotated for amino acids on day 14 increased by 9.83% compared to controls. It is speculated that diapause soybean hawkmoths may up-regulate amino acid metabolism by reducing E. casseliflavus abundance to maintain their nutritional balance. Additionally, tetracycline, chloromycetin and ampicillin were screened as the top three antibiotics against E. casseliflavus.

Discussion

This study not only extends our knowledge of gut microbiome in soybean hawkmoths at the species level, but also provides an initial investigation of gene functionality in interaction with insect hosts.

Male manipulation impinges on social-dependent tumor suppression in Drosophila melanogaster females

Physiological status can influence social behavior, which in turn can affect physiology and health. Previously, we reported that tumor growth in Drosophila virgin females depends on the social context, but did not investigate the underlying physiological mechanisms. Here, we sought to characterize the signal perceived between tumorous flies, ultimately discovering that the tumor suppressive effect varies depending on reproductive status. Firstly, we show that the tumor suppressive effect is neither dependent on remnant pheromone-like products nor on the microbiota. Transcriptome analysis of the heads of these tumorous flies reveals social-dependent gene-expression changes related to nervous-system activity, suggesting that a cognitive-like relay might mediate the tumor suppressive effect. The transcriptome also reveals changes in the expression of genes related to mating behavior. Surprisingly, we observed that this social-dependent tumor-suppressive effect is lost in fertilized females. After mating, Drosophila females change their behavior-favoring offspring survival-in response to peptides transferred via the male ejaculate, a phenomenon called "male manipulation". Remarkably, the social-dependent tumor suppressive effect is restored in females mated by sex-peptide deficient males. Since male manipulation has likely been selected to favor male gene transmission, our findings indicate that this evolutionary trait impedes social-dependent tumor growth slowdown.

A CTL - Lys immune function maintains insect metamorphosis by preventing gut bacterial dysbiosis and limiting opportunistic infections

BACKGROUND

Gut bacteria are beneficial to the host, many of which must be passed on to host offspring. During metamorphosis, the midgut of holometabolous insects undergoes histolysis and remodeling, and thus risks losing gut bacteria. Strategies employed by holometabolous insects to minimize this risk are obscure. How gut bacteria affect host insects after entering the hemocoel and causing opportunistic infections remains largely elusive.

RESULTS

We used holometabolous Helicoverpa armigera as a model and found low Lactobacillus load, high level of a C-type lectin (CTL) gene CD209 antigen-like protein 2 (CD209) and its downstream lysozyme 1 (Lys1) in the midgut of the wandering stage. CD209 or Lys1 depletion increased the load of midgut Lactobacillus, which further translocate to the hemocoel. In particular, CD209 or Lys1 depletion, injection of Lactobacillus plantarum, or translocation of midgut L. plantarum into the hemocoel suppressed 20-hydroxyecdysone (20E) signaling and delayed pupariation. Injection of L. plantarum decreased triacylglycerol and cholesterol storage, which may result in insufficient energy and 20E available for pupariation. Further, Lysine-type peptidoglycan, the major component of gram-positive bacterial cell wall, contributed to delayed pupariation and decreased levels of triacylglycerols, cholesterols, and 20E, in both H. armigera and Drosophila melanogaster.

CONCLUSIONS

A mechanism by which (Lactobacillus-induced) opportunistic infections delay insect metamorphosis was found, namely by disturbing the homeostasis of lipid metabolism and reducing 20E production. Moreover, the immune function of CTL - Lys was characterized for insect metamorphosis by maintaining gut homeostasis and limiting the opportunistic infections.

Honeybee symbiont Bombella apis could restore larval-to-pupal transition disrupted by antibiotic treatment

Numerous studies have demonstrated the vital roles of gut microbes in the health, immunity, nutrient metabolism, and behavior of adult worker honeybees. However, a few studies have been conducted on gut microbiota associated with the larval stage of honeybees. In the present study, we explored the role of a gut bacterium in larval development and larval-pupal transition in the Asian honeybee, Apis cerana. First, our examination of gut microbial profiling showed that Bombella apis, a larvae-associated bacterium, was the most dominant bacterium colonized in the fifth instar larvae. Second, we demonstrated that tetracycline, an antibiotic used to treat a honeybee bacterial brood disease, could cause the complete depletion of gut bacteria. This antibiotic-induced gut microbiome depletion in turn, significantly impacted the survivorship, pupation rate and emergence rate of the treated larvae. Furthermore, our analysis of gene expression pattens revealed noteworthy changes in key genes. The expression of genes responsible for encoding storage proteins vitellogenin (vg) and major royal jelly protein 1 (mrjp1) was significantly down-regulated in the tetracycline-treated larvae. Concurrently, the expression of krüppel homolog 1(kr-h1), a pivotal gene in endocrine signaling, increased, whilethe expression of broad-complex (br-c) gene that plays a key role in the ecdysone regulation decreased. These alterations indicated a disruption in the coordination of juvenile hormone and ecdysteroid synthesis. Finally, we cultivated B. apis isolated from the fifth instar worker larval of A. cerana and fed tetracycline-treated larvae with a diet replenished by B. apis. This intervention resulted in a significant improvement in the pupation rate, emergence rate, and overall survival rate of the treated larvae. Our findings demonstrate the positive impact of B. apis on honeybee larvae development, providing new evidence of the functional capacities of gut microbes in honeybee growth and development.