The gut symbiont Sphingomonas mediates imidacloprid resistance in the important agricultural insect pest Aphis gossypii Glover

Uninheritable but Widespread Bacterial Symbiont Enterococcus casseliflavus Mediates Detoxification of the Insecticide Chlorantraniliprole in the Agricultural Invasive Pest Spodoptera frugiperda

Host-symbiont interaction plays a crucial role in determining the host's fitness under toxic stress, as observed in numerous insect species. However, the mechanism of the symbionts involved in the detoxification of insecticides remains poorly known. In this study, through microbiome, proteomic, and genomic analysis, we identified a prevalent symbiont, Enterococcus casseliflavus EMBL-3, in a major invasive insect pest,Spodoptera frugiperda. This symbiont enhances the host's insecticide resistance to chlorantraniliprole by breaking amide bonds and dehalogenating insecticides. Complying with the increase in exposure risk of chlorantraniliprole, the E. casseliflavus isolates of insects' symbionts but not those from mammals or environmental strains showed a significant enrichment of potential chlorantraniliprole degradation genes. EMBL-3 is popular in field population insects with efficient horizontal transmission ability through cross-diet and cannibalism. This study provides a new therapeutic target for agricultural pests based on symbiont-targeted insect control for global crop protection.

Bacterial Symbionts Contribute to Insecticide Susceptibility of Diaphorina citri via Changing the Expression Level of Host Detoxifying Genes

Insecticide susceptibility is mainly determined by the insect host, but symbiotic bacteria are also an important affecting factor. In this study, we investigate the relationship between the structure of gut bacterial symbionts and insecticide susceptibility in Diaphorina citri, the important carrier of Candidatus Liberibacter asiaticus (CLas), the causal agent of Huanglongbing (HLB). Our results indicated that antibiotic treatment significantly increased the susceptibility of D. citri to bifenthrin and thiamethoxam, and significantly decreased the relative abundance of Wolbachia and Profftella, enzyme activities of CarEs, and expression level of multiple CarE genes. The relative loads of Wolbachia and Profftella were positively correlated with DcitCCE13, DcitCCE14, DcitCCE15, and DcitCCE16. RNAi and prokaryotic expression revealed that DcitCCE15 is associated with bifenthrin metabolism. These results revealed that bacterial symbionts might regulate DcitCCE15 expression, which is involved in the susceptibility of D. citri to bifenthrin.

Advancements in bacterial chemotaxis: Utilizing the navigational intelligence of bacteria and its practical applications

The fascinating world of microscopic life unveils a captivating spectacle as bacteria effortlessly maneuver through their surroundings with astonishing accuracy, guided by the intricate mechanism of chemotaxis. This review explores the complex mechanisms behind this behavior, analyzing the flagellum as the driving force and unraveling the intricate signaling pathways that govern its movement. We delve into the hidden costs and benefits of this intricate skill, analyzing its potential to propagate antibiotic resistance gene while shedding light on its vital role in plant colonization and beneficial symbiosis. We explore the realm of human intervention, considering strategies to manipulate bacterial chemotaxis for various applications, including nutrient cycling, algal bloom and biofilm formation. This review explores the wide range of applications for bacterial capabilities, from targeted drug delivery in medicine to bioremediation and disease control in the environment. Ultimately, through unraveling the intricacies of bacterial movement, we can enhance our comprehension of the intricate web of life on our planet. This knowledge opens up avenues for progress in fields such as medicine, agriculture, and environmental conservation.

Segregation of endosymbionts in complex symbiotic system of cicadas providing novel insights into microbial symbioses and evolutionary dynamics of symbiotic organs in sap-feeding insects

The most extraordinary systems of symbiosis in insects are found in the suborder Auchenorrhyncha of Hemiptera, which provide unique perspectives for uncovering complicated insect-microbe symbiosis. We investigated symbionts associated with bacteriomes and fat bodies in six cicada species, and compared transmitted cell number ratio of related symbionts in ovaries among species. We reveal that Sulcia and Hodgkinia or a yeast-like fungal symbiont (YLS) are segregated from other host tissues by the bacteriomes in the nymphal stage, then some of them may migrate to other organs (i.e., fat bodies and ovaries) during host development. Particularly, YLS resides together with Sulcia in the "symbiont ball" of each egg and the bacteriomes of young-instar nymphs, but finally migrates to the fat bodies of adults in the majority of Hodgkinia-free cicadas, whereas it resides in both bacteriome sheath and fat bodies of adults in a few other species. The transmitted Sulcia/YLS or Sulcia/Hodgkinia cell number ratio in ovaries varies significantly among species, which could be related to the distribution and/or lineage splitting of symbiont(s). Rickettsia localizes to the nuclei of bacteriomes and fat bodies in some species, but it was not observed to be transmitted to the ovaries, indicating that this symbiont may be acquired from environments or from father to offspring. The considerable difference in the transovarial transmission process of symbionts suggests that cellular mechanisms underlying the symbiont transmission are complex. Our results may provide novel insights into insect-microbe symbiosis.

Microbial Symbiont-Based Detoxification of Different Phytotoxins and Synthetic Toxic Chemicals in Insect Pests and Pollinators

Insects are the most diverse form of life, and as such, they interact closely with humans, impacting our health, economy, and agriculture. Beneficial insect species contribute to pollination, biological control of pests, decomposition, and nutrient cycling. Pest species can cause damage to agricultural crops and vector diseases to humans and livestock. Insects are often exposed to toxic xenobiotics in the environment, both naturally occurring toxins like plant secondary metabolites and synthetic chemicals like herbicides, fungicides, and insecticides. Because of this, insects have evolved several mechanisms of resistance to toxic xenobiotics, including sequestration, behavioral avoidance, and enzymatic degradation, and in many cases had developed symbiotic relationships with microbes that can aid in this detoxification. As research progresses, the important roles of these microbes in insect health and function have become more apparent. Bacterial symbionts that degrade plant phytotoxins allow host insects to feed on otherwise chemically defended plants. They can also confer pesticide resistance to their hosts, especially in frequently treated agricultural fields. It is important to study these interactions between insects and the toxic chemicals they are exposed to in order to further the understanding of pest insect resistance and to mitigate the negative effect of pesticides on nontarget insect species like Hymenopteran pollinators.

Microbiome toxicology - bacterial activation and detoxification of insecticidal compounds

Insect gut bacteria have been implicated in a myriad of physiological processes from nutrient supplementation to pathogen protection. In fact, symbiont-mediated insecticide degradation has helped explain sudden control failure in the field to a range of active ingredients. The mechanisms behind the loss of susceptibility are varied based on host, symbiont, and insecticide identity. However, while some symbionts directly break down pesticides, others modulate endogenous host detoxification pathways or involve reciprocal degradation of insecticidal and bactericidal compounds both inspiring new questions and requiring the reexamination of past conclusions. Good steward of the chemical pesticide arsenal requires consideration of these ecological interactions from development to deployment.

Mesoporous silica nanospheres-mediated insecticide and antibiotics co-delivery system for synergizing insecticidal toxicity and reducing environmental risk of insecticide

Mesoporous silica nanoparticles (MSNs) are efficient carriers of drugs, and are promising in developing novel pesticide formulations. The cotton aphids Aphis gossypii Glover is a world devastating insect pest. It has evolved high level resistance to various insecticides thus resulted in the application of higher doses of insecticides, which raised environmental risk. In this study, the MSNs based pesticide/antibiotic delivery system was constructed for co-delivery of ampicillin (Amp) and imidacloprid (IMI). The IMI@Amp@MSNs complexes have improved toxicity against cotton aphids, and reduced acute toxicity to zebrafish. From the 16S rDNA sequencing results, Amp@MSNs, prepared by loading ampicillin to the mesoporous of MSNs, greatly disturbed the gut community of cotton aphids. Then, the relative expression of at least 25 cytochrome P450 genes of A. gossypii was significantly suppressed, including CYP6CY19 and CYP6CY22, which were found to be associated with imidacloprid resistance by RNAi. The bioassay results indicated that the synergy ratio of ampicillin to imidacloprid was 1.6, while Amp@MSNs improved the toxicity of imidacloprid by 2.4-fold. In addition, IMI@Amp@MSNs significantly improved the penetration of imidacloprid, and contributed to the amount of imidacloprid delivered to A. gossypii increased 1.4-fold. Thus, through inhibiting the relative expression of cytochrome P450 genes and improving penetration of imidacloprid, the toxicity of IMI@Amp@MSNs was 6.0-fold higher than that of imidacloprid. The greenhouse experiments further demonstrated the enhanced insecticidal activity of IMI@Amp@MSNs to A. gossypii. Meanwhile, the LC50 of IMI@Amp@MSNs to zebrafish was 3.9-fold higher than that of IMI, and the EC50 for malformation was 2.8-fold higher than IMI, respectively, which indicated that the IMI@Amp@MSNs complexes significantly reduced the environmental risk of imidacloprid. These findings encouraged the development of pesticide/antibiotic co-delivery nanoparticles, which would benefit pesticide reduction and environmental safety.

Nicotinamide deficiency promotes imidacloprid resistance via activation of ROS/CncC signaling pathway-mediated UGT detoxification in Nilaparvata lugens

Metabolic alternation is a typical characteristic of insecticide resistance in insects. However, mechanisms underlying metabolic alternation and how altered metabolism in turn affects insecticide resistance are largely unknown. Here, we report that nicotinamide levels are decreased in the imidacloprid-resistant strain of Nilaparvata lugens, may due to reduced abundance of the symbiotic bacteria Arsenophonus. Importantly, the low levels of nicotinamide promote imidacloprid resistance via metabolic detoxification alternation, including elevations in UDP-glycosyltransferase enzymatic activity and enhancements in UGT386B2-mediated metabolism capability. Mechanistically, nicotinamide suppresses transcriptional regulatory activities of cap 'n' collar isoform C (CncC) and its partner small muscle aponeurosis fibromatosis isoform K (MafK) by scavenging the reactive oxygen species (ROS) and blocking the DNA binding domain of MafK. In imidacloprid-resistant N. lugens, nicotinamide deficiency re-activates the ROS/CncC signaling pathway to provoke UGT386B2 overexpression, thereby promoting imidacloprid detoxification. Thus, nicotinamide metabolism represents a promising target to counteract imidacloprid resistance in N. lugens.

Sphingomonas bacteria could serve as an early bioindicator for the development of chlorantraniliprole resistance in Spodoptera frugiperda

The fall armyworm (Spodoptera frugiperda) was found to have invaded China in December 2018, and in just one year, crops in 26 provinces were heavily affected. Currently, the most effective method for emergency control of fulminant pests is to use of chemical pesticides. Recently, most fall armyworm populations in China were begining to exhibite low level resistance to chlorantraniliprole. At present, it is not possible to sensitively reflect the low level resistance of S. frugiperda by detecting target mutation and detoxification enzyme activity. In this study we found that 12 successive generations of screening with chlorantraniliprole caused S. frugiperda to develop low level resistance to this insecticide, and this phenotype was not attribute to genetic mutations in S. frugiperda, but rather to a marked increase in the relative amount of the symbiotic bacteria Sphingomonas. Using FISH and qPCR assays, we determined the amount of Sphingomonas in the gut of S. frugiperda and found Sphingomonas accumulation to be highest in the 3rd-instar larvae. Additionally, Sphingomonas was observed to provide a protective effect to against chlorantraniliprole stress to S. frugiperda. With the increase of the resistance to chlorantraniliprole, the abundance of bacteria also increased, we propose Sphingomonas monitoring could be adapted into an early warning index for the development of chlorantraniliprole resistance in S. frugiperda populations, such that timely measures can be taken to delay or prevent the widespread propagation of resistance to this highly useful agricultural chemical in S. frugiperda field populations.

Rifampicin synergizes the toxicity of insecticides against the green peach aphid, Myzus persicae

Myzus persicae is an important pest that has developed resistance to nearly all currently used insecticidal products. The employment of insecticide synergists is one of the effective strategies that need to be developed for the management of this resistance. Our study showed that treatment with a combination of the antibiotic, rifampicin, with imidacloprid, cyantraniliprole, or clothianidin significantly increased their toxicities against M. persicae, by 2.72, 3.59, and 2.41 folds, respectively. Rifampicin treatment led to a noteworthy reduction in the activities of multifunctional oxidases (by 32.64%) and esterases (by 23.80%), along with a decrease in the expression of the CYP6CY3 gene (by 58.57%) in M. persicae. It also negatively impacted the fitness of the aphids, including weight, life span, number of offspring, and elongation of developmental duration. In addition, bioassays showed that the combination of rifampicin and a detoxification enzyme inhibitor, piperonyl butoxide, or dsRNA of CYP6CY3 further significantly improved the toxicity of imidacloprid against M. persicae, by 6.19- and 7.55-fold, respectively. The present study suggests that development of active ingredients such as rifampicin as candidate synergists, show promise to overcome metabolic resistance to insecticides in aphids.

Severe fever with thrombocytopenia syndrome virus infection shapes gut microbiome of the tick vector Haemaphysalis longicornis

BACKGROUND

Ticks serve as vectors for a diverse array of pathogens, including viruses responsible for both human and livestock diseases. Symbiotic bacteria hold significant potential for controlling tick-borne disease. However, the alteration of tick gut bacterial community in response to pathogen infection has not been analyzed for any tick-borne viruses. Here, the impact of severe fever with thrombocytopenia syndrome virus (SFTSV) infection on bacterial diversity in the gut of Haemaphysalis longicornis is investigated.

METHODS

Unfed tick females were artificially infected with SFTSV. The gut samples were collected and the genomic DNA was extracted. We then investigated alterations in gut bacterial composition in response to SFTSV infection through 16S rRNA gene sequencing.

RESULTS

The study found that a reduction in the number of operational taxonomic units (OTUs) in the tick gut following SFTSV infection. However, there were no significant changes in alpha diversity indices upon infection. Four genera, including Corynebacterium, Arthrobacter, Sphingomonas, and Escherichia, were identified as biomarkers for the tick gut without SFTSV infection. Notably, the predicted correlation network indicated that the biomarkers Sphingomonas and Escherichia exhibited positive correlations within the same subcommunity, which was altered upon viral infection.

CONCLUSIONS

These findings revealed that the change in tick gut bacterial composition upon SFTSV infection and could facilitate the discovery new target for tick-borne viral disease control.

The symbiont Wolbachia alleviates pesticide susceptibility in the two-spotted spider mite Tetranychus urticae through enhanced host detoxification pathways

The two-spotted spider mite (Tetranychus urticae) is one of the most well-known pesticide-resistant agricultural pests, with resistance often attributed to changes such as target-site mutations and detoxification activation. Recent studies show that pesticide resistance can also be influenced by symbionts, but their involvement in this process in spider mites remains uncertain. Here, we found that infection with Wolbachia, a well-known bacterial reproductive manipulator, significantly increased mite survival after exposure to the insecticides abamectin, cyflumetofen, and pyridaben. Wolbachia-infected (WI) mites showed higher expression of detoxification genes such as P450, glutathione-S-transferase (GST), ABC transporters, and carboxyl/cholinesterases. RNA interference experiments confirmed the role of the two above-mentioned detoxification genes, TuCYP392D2 and TuGSTd05, in pesticide resistance. Increased GST activities were also observed in abamectin-treated WI mites. In addition, when wild populations were treated with abamectin, WI mites generally showed better survival than uninfected mites. However, genetically homogeneous mites with different Wolbachia strains showed similar survival. Finally, abamectin treatment increased Wolbachia abundance without altering the mite's bacterial community. This finding highlights the role of Wolbachia in orchestrating pesticide resistance by modulating host detoxification. By unraveling the intricate interplay between symbionts and pesticide resistance, our study lays the groundwork for pioneering strategies to combat agricultural pests.

The application of entomopathogenic nematode modified microbial communities within nesting mounds of the red imported fire ants, Solenopsis invicta

Entomopathogenic microorganisms (e.g., fungi, bacteria, nematodes) have been widely used in biological control of soil-dwelling pests, including the red imported fire ant (RIFA), Solenopsis invicta, a notorious invasive pest worldwide. The application of large amounts of entomopathogenic microorganisms to soil may affect the indigenous soil microbial communities. However, reports about the effect of entomopathogenic nematodes (EPN) on soil microbial communities are very few. In this study, the effects of EPN on RIFA populations and microbial communities in mounds were investigated. Our results showed that the application of the EPN Steinernema carpocapsae. All strain on mounds efficaciously suppressed RIFA worker populations, without forming significantly more satellite mounds compared with the control treatment. The application of EPN did not impact the bacterial and fungal diversity in soils derived from the RIFA mounds. However, it slightly altered the taxonomic make-up of the bacterial communities, but significantly altered the taxonomic composition of fungal communities at the phylum, family, and genus levels. The abundances of some beneficial bacteria and fungi, such as Streptomyces, decreased, while those of plant and animal pathogenic bacteria and fungi, dramatically increased, after EPN treatment. On the other hand, the abundances of some entomopathogenic fungi, such as Fusicolla, Clonostachys, and Mortierella, increased. Redundancy analysis or canonical correspondence analysis revealed a positive correlation between the efficacious EPN control and the presence of the insect-resistant bacteria, Sinomonas, as well as entomopathogenic fungi Fusicolla and Mortierella. This suggests that the interactions between EPN and entomopathogenic fungi may play a role in the biological control of RIFA. Our discoveries shed light on the interactions among EPN, RIFA, and soil microbial communities, and emphasize a possible mutualistic relationship between EPN and entomopathogenic fungi in the biological control of RIFA.

Design, Synthesis, and Synergistic Activities of Eight-Membered Carbon Bridged Neonicotinoid Derivatives

Insecticide synergists are an effective approach to increase the control efficacy and reduce active ingredient usage. In order to explore neonicotinoid-specific synergists with novel scaffolds and higher potency, a series of eight-membered carbon bridged neonicotinoid derivatives were designed and synthesized in accordance with our previous research. The synergistic effects of the target compounds on neonicotinoids in Aphis craccivora were evaluated, and the structure-activity relationships were summarized. The results indicated that most of the target compounds exhibited significant synergistic effects on imidacloprid in A. craccivora at low concentrations. In particular, compound 1 at a concentration of 1 mg/L reduced the LC50 value of imidacloprid from 0.856 mg/L to 0.170 mg/L. Meanwhile, compound 1 also increased the insecticidal activity of most neonicotinoid insecticides belonging to the Insecticide Resistance Action Committee (IRAC) 4 A subgroup against A. craccivora. The present study might be meaningful for directing the design of neonicotinoid-specific synergists.

Coping with extremes: Alternations in diet, gut microbiota, and hepatic metabolic functions in a highland passerine

In wild animals, diet and gut microbiota interactions are critical moderators of metabolic functions and are highly contingent on habitat conditions. Challenged by the extreme conditions of high-altitude environments, the strategies implemented by highland animals to adjust their diet and gut microbial composition and modulate their metabolic substrates remain largely unexplored. By employing a typical human commensal species, the Eurasian tree sparrow (Passer montanus, ETS), as a model species, we studied the differences in diet, digestive tract morphology and enzyme activity, gut microbiota, and metabolic energy profiling between highland (the Qinghai-Tibet Plateau, QTP; 3230 m) and lowland (Shijiazhuang, Hebei; 80 m) populations. Our results showed that highland ETSs had enlarged digestive organs and longer small intestinal villi, while no differences in key digestive enzyme activities were observed between the two populations. The 18S rRNA sequencing results revealed that the dietary composition of highland ETSs were more animal-based and less plant-based than those of the lowland ones. Furthermore, 16S rRNA sequencing results suggested that the intestinal microbial communities were structurally segregated between populations. PICRUSt metagenome predictions further indicated that the expression patterns of microbial genes involved in material and energy metabolism, immune system and infection, and xenobiotic biodegradation were strikingly different between the two populations. Analysis of liver metabolomics revealed significant metabolic differences between highland and lowland ETSs in terms of substrate utilization, as well as distinct sex-specific alterations in glycerophospholipids. Furthermore, the interplay between diet, liver metabolism, and gut microbiota suggests a dietary shift resulting in corresponding changes in gut microbiota and metabolic functions. Our findings indicate that highland ETSs have evolved to optimize digestion and absorption, rely on more protein-rich foods, and possess gut microbiota tailored to their dietary composition, likely adaptive physiological and ecological strategies adopted to cope with extreme highland environments.

Comparative metaproteomics reveal co-contribution of onion maggot and its gut microbiota to phoxim resistance

Pesticide resistance inflicts significant economic losses on a global scale each year. To address this pressing issue, substantial efforts have been dedicated to unraveling the resistance mechanisms, particularly the newly discovered microbiota-derived pesticide resistance in recent decades. Previous research has predominantly focused on investigating microbiota-derived pesticide resistance from the perspective of the pest host, associated microbes, and their interactions. However, a gap remains in the quantification of the contribution by the pest host and associated microbes to this resistance. In this study, we investigated the toxicity of phoxim by examining one resistant and one sensitive Delia antiqua strain. We also explored the critical role of associated microbiota and host in conferring phoxim resistance. In addition, we used metaproteomics to compare the proteomic profile of the two D. antiqua strains. Lastly, we investigated the activity of detoxification enzymes in D. antiqua larvae and phoxim-degrading gut microbes, and assessed their respective contributions to phoxim resistance in D. antiqua. The results revealed contributions by D. antiqua and its gut bacteria to phoxim resistance. Metaproteomics showed that the two D. antiqua strains expressed different protein profiles. Detoxifying enzymes including Glutathione S-transferases, carboxylesterases, Superoxide Dismutase, Glutathione Peroxidase, and esterase B1 were overexpressed in the resistant strain and dominated in differentially expressed insect proteins. In addition, organophosphorus hydrolases combined with a group of ABC type transporters were overexpressed in the gut microbiota of resistant D. antiqua compared to the sensitive strain. 85.2% variation of the larval mortality resulting from phoxim treatment could be attributed to the combined effects of proteins from both from gut bacteria and D. antiqua, while the individual contribution of proteins from gut bacteria or D. antiqua alone accounted for less than 10% of the variation in larval mortality caused by phoxim. The activity of the overexpressed insect enzymes and the phoxim-degrading activity of gut bacteria in resistant D. antiqua larvae were further confirmed. This work enhances our understanding of microbiota-derived pesticide resistance and illuminates new strategies for controlling pesticide resistance in the context of insect-microbe mutualism.