A putative endonuclease reduces the efficiency of oral RNA interference in Nilaparvata lugens.

BACKGROUND: The RNA interference (RNAi) efficiency of double-stranded RNA (dsRNA) delivery to insects by various methods is different and the reduced efficacy of feeding dsRNA is partly due to the presence of DNA/RNA non-specific endonuclease in the insect gut. However, the mechanism leading to the low RNAi efficiency of Nilaparvata lugens by feeding remains elusive. RESULTS: In this study, we identified a putatively DNA/RNA non-specific endonuclease gene in the N. lugens genome database that was highly expressed in the first nymphal instar and the midgut. Different expression levels of NldsRNase after feeding and injection suggested that NldsRNase might interfere with oral RNAi in N. lugens. A co-delivery RNAi strategy further revealed that the presence of NldsRNase reduces RNAi efficiency. In vitro dsRNA degradation experiments also showed that the stability of dsRNA was higher in a gut mixture from nymphs injected with dsNldsRNase. These results support the idea that the low oral RNAi response observed in N. lugens is likely due to the presence of NldsRNase. CONCLUSIONS: Our study provides insight into the differences in RNAi response between the injection and feeding of dsRNA in N. lugens and sheds light on the mechanisms underlying the reduced efficacy of RNAi via feeding. These findings may help to inform the development of more-effective RNAi-based strategies controlling N. lugens and other insect pests. © 2024 Society of Chemical Industry.

Stimuli-triggered multilayer films in response to temperature and ionic strength changes for controlled favipiravir drug release.

The block copolymer micelles and natural biopolymers were utilized to form layer-by-layer (LbL) films via electrostatic interaction, which were able to effectively load and controllably release favipiravir, a potential drug for the treatment of coronavirus epidemic. The LbL films demonstrated reversible swelling/shrinking behavior along with the manipulation of temperature, which could also maintain the integrity in the structure and the morphology. Due to dehydration of environmentally responsive building blocks, the drug release rate from the films was decelerated by elevating environmental temperature and ionic strength. In addition, the pulsed release of favipiravir was observed from the multilayer films under the trigger of temperature, which ensured the precise control in the content of the therapeutic reagents at a desired time point. The nanoparticle-based LbL films could be used for on-demandin vitrorelease of chemotherapeutic reagents.

Genome-wide analysis of DNA methylation in pseudomyxoma peritonei originated from appendiceal neoplasms.

INTRODUCTION: Pseudomyxoma peritonei (PMP) is a disease characterized by progressive accumulation of intraperitoneal mucinous ascites produced by neoplasms in the abdominal cavity. Since the prognosis of patients with PMP remain unsatisfactory, the development of effective therapeutic drug(s) is a matter of pressing concern. Genetic analyses of PMP have clarified the frequent activation of GNAS and/or KRAS. However, the involvement of global epigenetic alterations in PMPs has not been reported. METHODS: To clarify the genetic background of the 15 PMP tumors, we performed genetic analysis using AmpliSeq Cancer HotSpot Panel v2. We further investigated global DNA methylation in the 15 tumors and eight non-cancerous colonic epithelial cells using Methylation EPIC array BeadChip (Infinium 850k) containing a total of 865,918 probes. RESULTS: This is the first report of comprehensive DNA methylation profiles of PMPs in the world. We clarified that the 15 PMPs could be classified into at least two epigenotypes, unique methylation epigenotype (UME) and normal-like methylation epigenotype (NLME), and that genes associated with neuronal development and synaptic signaling may be involved in the development of PMPs. In addition, we identified a set of hypermethylation marker genes such as HOXD1 and TSPYL5 in the 15 PMPs. CONCLUSIONS: These findings may help the understanding of the molecular mechanism(s) of PMP and contribute to the development of therapeutic strategies for this life-threatening disease.

Unintended consequences: Disrupting microbial communities of Nilaparvata lugens with non-target pesticides.

Insects are frequently exposed to a range of insecticides that can alter the structure of the commensal microbiome. However, the effects of exposure to non-target pesticides (including non-target insecticides and fungicides) on insect pest microbiomes are still unclear. In the present study, we exposed Nilaparvata lugens to three target insecticides (nitenpyram, pymetrozine, and avermectin), a non-target insecticide (chlorantraniliprole), and two fungicides (propiconazole and tebuconazole), and observed changes in the microbiome's structure and function. Our results showed that both non-target insecticide and fungicides can disrupt the microbiome's structure. Specifically, symbiotic bacteria of N. lugens were more sensitive to non-target insecticide compared to target insecticide, while the symbiotic fungi were more sensitive to fungicides. We also found that the microbiome in the field strain was more stable under pesticides exposure than the laboratory strain (a susceptible strain), and core microbial species g_Pseudomonas, s_Acinetobacter soli, g_Lactobacillus, s_Metarhizium minus, and s_Penicillium citrinum were significantly affected by specifically pesticides. Furthermore, the functions of symbiotic bacteria in nutrient synthesis were predicted to be significantly reduced by non-target insecticide. Our findings contribute to a better understanding of the impact of non-target pesticides on insect microbial communities and highlight the need for scientific and rational use of pesticides.

The insecticidal activity and mechanism of tebuconazole on Nilaparvata lugens (Stål).

BACKGROUND: Previous studies have shown that fungicides have insecticidal activity that can potentially be used as an insecticide resistance management strategy in the brown planthopper Nilaparvata lugens (Stål). However, the mechanism that induces mortality of N. lugens remains elusive. RESULTS: In the present study, the insecticidal activities of 14 fungicides against N. lugens were determined, of which tebuconazole had the highest insecticidal activity compared with the other fungicides. Furthermore, tebuconazole significantly inhibited the expression of the chitin synthase gene NlCHS1; the chitinase genes NlCht1, NlCht5, NlCht7, NlCht9, and NlCht10; and the ß-N-acetylhexosaminidase genes NlHex3, NlHex4, NlHex5 and NlHex6; it significantly suppressed the expression of ecdysteroid biosynthetic genes as well, including SDR, CYP307A2, CYP307B1, CYP306A2, CYP302A1, CYP315A1 and CYP314A1 of N. lugens. Additionally, tebuconazole affected the diversity, structure, composition, and function of the symbiotic fungi of N. lugens, as well as the relative abundance of saprophytes and pathogens, suggesting that tebuconazole reshapes the diversity and function of symbiotic fungi of N. lugens. CONCLUSION: Our findings illustrate the insecticidal mechanism of tebuconazole, possibly by inhibiting normal molting or disrupting microbial homeostasis in N. lugens, and provide an important rationale for developing novel insect management strategies to delay escalating insecticide resistance. © 2023 Society of Chemical Industry.

Microbiome variation correlates with the insecticide susceptibility in different geographic strains of a significant agricultural pest, Nilaparvata lugens.

Microbiome-mediated insecticide resistance is an emerging phenomenon found in insect pests. However, microbiome composition can vary by host genotype and environmental factors, but how these variations may be associated with insecticide resistance phenotype remains unclear. In this study, we compared different field and laboratory strains of the brown planthopper Nilaparvata lugens in their microbiome composition, transcriptome, and insecticide resistance profiles to identify possible patterns of correlation. Our analysis reveals that the abundances of core bacterial symbionts are significantly correlated with the expression of several host detoxifying genes (especially NlCYP6ER1, a key gene previously shown involved in insecticides resistance). The expression levels of these detoxifying genes correlated with N. lugens insecticide susceptibility. Furthermore, we have identified several environmental abiotic factors, including temperature, precipitation, latitude, and longitude, as potential predictors of symbiont abundances associated with expression of key detoxifying genes, and correlated with insecticide susceptibility levels of N. lugens. These findings provide new insights into how microbiome-environment-host interactions may influence insecticide susceptibility, which will be helpful in guiding targeted microbial-based strategies for insecticide resistance management in the field.

Novel Strategy to fabricate Antiwrinkle Cotton fabrics with 1,2,3,4-Butanetetracarboxylic Acid under a Low Temperature.

As a most promising formaldehyde-free crosslinking agent for the antiwrinkle treatment of cotton fabrics, 1,2,3,4-butanetetracarboxylic acid (BTCA) has been explored for many years to replace the traditional N-methylol resin. However, the current methodology for preparing antiwrinkle cotton fabrics with BTCA mainly highlights the troublesome problem of higher curing temperature. In this research, a novel strategy with the aid of dimethyl sulfone (MSM) was developed to decrease the curing temperature of BTCA for fabricating antiwrinkle cotton fabrics, which is an eco-friendly additive with low price and wonderful biocompatibility. Temperature-dependent Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and computational simulations were employed to analyze the mechanism of MSM in the overall reaction between BTCA and cellulose. Based on the strong hydrogen-bond acceptor property of MSM, the noncovalent interactions in the crosslinking system could be easily interrupted, which facilitates the BTCA diffusion in amorphous regions of cellulose, anhydride formation, and the thermal vibration of cellulose chains during the processing. Physically and chemically speaking, both reactivities of grafting and crosslinking reactions of BTCA are significantly increased with the assistance of MSM, consequently reducing the curing temperature, which will hopefully help achieve the industrial-scale application of BTCA in antiwrinkle treatment.

Steric Effects in the Deposition Mode and Drug-Delivering Efficiency of Nanocapsule-Based Multilayer Films.

Using surface-initiated atom transfer radical polymerization (ATRP), block polymers with a series of quaternization degrees were coated on the surface of silica nanocapsules (SNCs) by the "grafting-from" technique. Molnupiravir, an antiviral medicine urgently approved for the treatment of SARS-CoV-2, was encapsulated in polymer-coated SNCs and further incorporated into well-defined films with polystyrene sulfonate (PSS) homopolymers by layer-by-layer (LBL) self-assembly via electrostatic interactions. We investigated the impact of the quaternization degree of the polymers and steric hindrance of functional groups on the growth mode, swelling/deswelling transition, and drug-delivering efficiency of the obtained LBL films. The SNCs were derived from coronas of parent block polymers of matched molecular weights-poly(N-isopropylacrylamide)-block-poly(N,N-dimethylaminoethyl methacrylate) (PNIPAM-b-PDMAEMA)-by quaternization with methyl sulfate. As revealed by the data results, SNCs with coronas with higher quaternization degrees resulted in a larger layering distance of the film structure because of weaker ionic pairing (due to the presence of a bulky methyl spacer) between SNCs and PSS. Interestingly, when comparing the drug release profile of the encapsulated drugs from SNC-based films, the release rate was slower in the case of capsule coronas with higher quaternization degrees because of the larger diffusion distance of the encapsulated drugs and stronger hydrophobic-hydrophobic interactions between SNCs and drug molecules.

Insecticide Susceptibility and Mechanism of Spodoptera frugiperda on Different Host Plants.

Spodoptera frugiperda (J. E. Smith) is a worldwide economically important crop pest. Although the individuals of S. frugiperda that invaded China have been characterized as the corn strain, they also have the ability to damage other crops in China. The physiological and behavioral responses of S. frugiperda to different host plants are poorly understood. In the present study, we investigated the host plant preference, fitness costs, and differences in detoxification gene expression and microbiome composition between two S. frugiperda strains that fed on different crop plant diets. The results showed that S. frugiperda larvae exhibited no obvious preference for corn or rice, but significant suppression of development was observed in the rice-fed strain. In addition, the corn-fed strain showed higher insecticide tolerance and detoxification enzyme activities than the rice-fed strain. Moreover, multiple detoxification genes were upregulated in the corn-fed strain, and microbiome composition variation was observed between the two strains. Together, the results suggest that population-specific plasticity is related to host plant diets in S. frugiperda. These results provide a theoretical basis for the evolution of resistance differences in S. frugiperda and are helpful for designing resistance management strategies for S. frugiperda aimed at different crops.

miRNA novel_268 targeting NlABCG3 is involved in nitenpyram and clothianidin resistance in Nilaparvata lugens.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests that seriously threatens the high-quality and safe production of rice. However, due to the unscientific use of chemical insecticides, N. lugens has developed varying levels of resistance to insecticides, including nitenpyram and clothianidin. The ATP-binding cassette (ABC) transporter plays a nonnegligible role in phase III of the detoxification process, which may play an important role in insecticide resistance. In the present study, NlABCG3 was significantly overexpressed in both the NR and CR populations compared with susceptible populations. Silencing NlABCG3 significantly increased the susceptibility of BPH to nitenpyram and clothianidin. In addition, RNAi-mediated knockdown of three key genes in the miRNA biogenesis pathway altered the level of NlABCG3. Subsequently, the luciferase reporter assays demonstrated that novel_268 binds to the NlABCG3 coding region and downregulates its expression. Furthermore, injection of miRNA inhibitors or mimics of novel_268 significantly altered the susceptibility of N. lugens to nitenpyram and clothianidin. These results suggest that miRNA novel_268 targeting NlABCG3 is involved in nitenpyram and clothianidin resistance in N. lugens. These findings may help to enhance our knowledge of the transcriptional regulation of the ABC transporter that mediate insecticide resistance in N. lugens.

Odorant binding protein 3 is associated with nitenpyram and sulfoxaflor resistance in Nilaparvata lugens.

Odorant binding protein (OBP) can interact with small-molecule compounds insecticides and thereby modulate variation in insecticide susceptibility in insects. However, the regulatory mechanism of OBP-mediated insecticide resistance in Nilaparvata lugens, a destructive rice pest in Asia, remains unclear. Here, we explored the role of NlOBP3 in the resistance of N. lugens to nitenpyram and sulfoxaflor. The results showed that NlOBP3 was overexpressed in association with nitenpyram and sulfoxaflor resistance, and NlOBP3 silencing significantly increased the mortality of N. lugens to nitenpyram and sulfoxaflor, suggesting that NlOBP3 may be associated with nitenpyram and sulfoxaflor resistance in N. lugens. OBP localization revealed that NlOBP3 was highly expressed in all nymph stages and was enriched in the antennae, legs, body wall, and fat body. RT-qPCR analyses showed that the mRNA levels of NlOBP3 were significantly affected by nitenpyram and sulfoxaflor. Additionally, molecular docking predicted that there were multiple binding sites that may played key roles in the binding of NlOBP3 with nitenpyram and sulfoxaflor. The current study identifies a previously undescribed mechanism of insecticide resistance in N. lugens, showing that NlOBP3 is likely to be involved in the evolution of nitenpyram and sulfoxaflor resistance in N. lugens.

Dynamics of Microbial Communities across the Life Stages of Nilaparvata lugens (Stål).

Understanding the composition of microorganismal communities hosted by insect pests is an important prerequisite for revealing their functions and developing new pest control strategies. Although studies of the structure of the microbiome of Nilaparvata lugens have been published, little is known about the dynamic changes in this microbiome across different developmental stages, and an understanding of the core microbiota is still lacking. In this study, we investigated the dynamic changes in bacteria and fungi in different developmental stages of N. lugens using high-throughput sequencing technology. We observed that the microbial diversity in eggs and mated adults was higher than that in nymphs and unmated adults. We also observed a notable strong correlation between fungal and bacterial α-diversity, which suggests that fungi and bacteria are closely linked and may perform functions collaboratively during the whole developmental period. Arsenophonus and Hirsutella were the predominant bacterial and fungal taxa, respectively. Bacteria were more conserved than fungi during the transmission of the microbiota between developmental stages. Compared with that in the nymph and unmated adult stages of N. lugens, the correlation between bacterial and fungal communities in the mated adult and egg stages was stronger. Moreover, the core microbiota across all developmental stages in N. lugens was identified, and there were more bacterial genera than fungal genera; notably, the core microbiota of eggs, nymphs, and mated and unmated adults showed distinctive functional enrichment. These findings highlight the potential value of further exploring microbial functions during different developmental stages and developing new pest management strategies.

Insecticide Resistance Monitoring in Field Populations of the Whitebacked Planthopper Sogatella furcifera (Horvath) in China, 2019-2020.

Monitoring is an important component of insecticide resistance management. In this study, resistance monitoring was conducted on 18 field populations in China. The results showed that S. furcifera developed high levels of resistance to chlorpyrifos and buprofezin, and S. furcifera showed low to moderate levels of resistance to imidacloprid, thiamethoxam, dinotefuran, clothianidin, sulfoxaflor, isoprocarb and ethofenprox. Sogatella furcifera remained susceptible or low levels of resistance to nitenpyram. LC50 values of nitenpyram and dinotefuran, imidacloprid, thiamethoxam, clothianidin and chlorpyrifos exhibited significant correlations, as did those between dinotefuran and thiamethoxam, clothianidin, sulfoxaflor, imidacloprid, isoprocarb and buprofezin. Similarly, significant correlations were observed between thiamethoxam and clothianidin, sulfoxaflor and imidacloprid. In addition, the activity of EST in field populations of S. furcifera were significantly correlated with the LC50 values of nitenpyram, thiamethoxam and clothianidin. These results will help inform effective insecticide resistance management strategies to delay the development of insecticide resistance in S. furcifera.

Decline in symbiont-dependent host detoxification metabolism contributes to increased insecticide susceptibility of insects under high temperature.

The interactions between insects and their bacterial symbionts are shaped by a variety of abiotic factors, including temperature. As global temperatures continue to break high records, a great deal of uncertainty surrounds how agriculturally important insect pests and their symbionts may be affected by elevated temperatures, and its implications for future pest management. In this study, we examine the role of bacterial symbionts in the brown planthopper Nilaparvata lugens response to insecticide (imidacloprid) under different temperature scenarios. Our results reveal that the bacterial symbionts orchestrate host detoxification metabolism via the CncC pathway to promote host insecticide resistance, whereby the symbiont-inducible CncC pathway acts as a signaling conduit between exogenous abiotic stimuli and host metabolism. However, this insect-bacterial partnership function is vulnerable to high temperature, which causes a significant decline in host-bacterial content. In particular, we have identified the temperature-sensitive Wolbachia as a candidate player in N. lugens detoxification metabolism. Wolbachia-dependent insecticide resistance was confirmed through a series of insecticide assays and experiments comparing Wolbachia-free and Wolbachia-infected N. lugens and also Drosophila melanogaster. Together, our research reveals elevated temperatures negatively impact insect-bacterial symbiosis, triggering adverse consequences on host response to insecticide (imidacloprid) and potentially other xenobiotics.

Dual oxidase-dependent reactive oxygen species are involved in the regulation of UGT overexpression-mediated clothianidin resistance in the brown planthopper, Nilaparvata lugens.

BACKGROUND: Uridine diphosphate-glycosyltransferases (UGTs) are phase II metabolic enzymes involved in metabolism of toxins and resistance to insecticides in insect pests. Reactive oxygen species (ROS) induced by xenobiotics are important for activation of detoxification pathways. However, relationships between ROS and UGTs involved in toxin metabolism and insecticide resistance remain unclear. RESULTS: Here, involvement of dual oxidase (Duox)-dependent ROS in regulating UGT expression-mediated insecticide resistance in the brown planthopper (Nilaparvata lugens) was investigated. The overexpression of NlUGT386F2 contributed to the resistance of N. lugens to clothianidin. Furthermore, the ROS inhibitor (N-acetylcysteine) significantly reduced the expression of NlUGT386F2 and increased the susceptibility of N. lugens to clothianidin. Silencing the ROS producer Duox significantly increased the susceptibility of N. lugens to clothianidin through the down-regulation of NlUGT386F2 expression. CONCLUSION: NlDuox-dependent ROS regulates NlUGT386F2 expression-mediated clothianidin resistance in brown planthopper. These observations further our understanding of the metabolism of toxins and of insecticide-resistance in insect pests.

Activator protein-1 mediated CYP6ER1 overexpression in the clothianidin resistance of Nilaparvata lugens (Stål).

BACKGROUND: Nilaparvata lugens, a destructive rice pest in Asia, has developed resistance to many insecticides, including the neonicotinoid clothianidin. CYP6ER1 plays an important role in N. lugens resistant to clothianidin, but only limited information on the transcriptional regulation of CYP6ER1 overexpression in clothianidin resistance is available. RESULTS: In this study, the transcription factor activator protein 1 (AP-1) was found to be overexpressed in a clothianidin-resistant strain of N. lugens and several field resistant populations. RNA interference-mediated silencing of NlAP-1 significantly decreased CYP6ER1 expression and increased the susceptibility of N. lugens to clothianidin. Additionally, NlAP-1 was highly expressed in egg and adult stages, and in midguts, and NlAP-1 was upregulated and induced to a greater extent in the clothianidin-resistant strain after exposure to clothianidin. Finally, dual-luciferase reporter assays confirmed the interaction between NlAP-1 and the two predicted binding sites in the CYP6ER1 promoter. CONCLUSION: NlAP-1 bound the -1388 to -1208-bp region of the CYP6ER1 promoter, enhancing its activity and then regulate the expression of CYP6ER1. These findings enhance our knowledge of the transcriptional regulation of the P450 genes that mediate insecticide resistance in insect pests. © 2021 Society of Chemical Industry.

Carboxylesterase genes in nitenpyram-resistant brown planthoppers, Nilaparvata lugens.

Carboxylesterases (CarEs) represent one of the major detoxification enzyme families involved in insecticide resistance. However, the function of specific CarE genes in insecticide resistance is still unclear in the insect Nilaparvata lugens (Stål), a notorious rice crop pest in Asia. In this study, a total of 29 putative CarE genes in N. lugens were identified, and they were divided into seven clades; further, the ß-esterase clade was significantly expanded. Tissue-specific expression analysis found that 17 CarE genes were abundantly distributed in the midgut and fat body, while 12 CarE genes were highly expressed in the head. The expression of most CarE genes was significantly induced in response to the challenge of nitenpyram, triflumezopyrim, chlorpyrifos, isoprocarb and etofenprox. Among these, the expression levels of NlCarE2, NlCarE4, NlCarE9, NlCarE17 and NlCarE24 were increased by each insecticide. Real-time quantitative polymerase chain reaction and RNA interference assays revealed the NlCarE1 gene to be a candidate gene mainly involved in nitenpyram resistance, while simultaneously silencing NlCarE1 and NlCarE19 produced a stronger effect than silencing either one individually, suggesting a cooperative relationship in resistance formation. These findings lay the foundation for further clarification of insecticide resistance mediated by CarE in N. lugens.

Wolbachia enhances expression of NlCYP4CE1 in Nilaparvata lugens in response to imidacloprid stress.

The brown planthopper, Nilaparvata lugens, is one of the main insect pests of rice. The N. lugens gene NlCYP4CE1 encodes cytochrome P450 monooxygenase (P450), which is a key enzyme in the metabolism of the insecticide imidacloprid. Previous research has suggested that the expression of NlCYP4CE1 is induced by imidacloprid stress, but the effect of bacterial symbionts on its expression has not been determined. The results of this study show that exposure to subtoxic imidacloprid changed the structure of the bacterial symbiont community in N. lugens. Specifically, the total bacterial content increased, but the bacterial species diversity significantly decreased. Wolbachia accounted for the largest proportion of bacteria in N. lugens; its abundance significantly increased after subtoxic imidacloprid exposure. The transcript level of NlCYP4CE1 was significantly increased by imidacloprid, but this effect was significantly weakened after Wolbachia was cleared with tetracycline. This result suggests that Wolbachia enhances the expression of NlCYP4CE1 to promote the detoxification metabolic response to imidacloprid stress. Understanding the effect of bacterial symbionts on gene expression in the host provides a new perspective on interactions between insecticides and their target insect pests, and highlights that subtoxic imidacloprid exposure may raise the risk of insecticide resistance by altering the structure of bacterial symbiont communities.

Transcriptional Response of ATP-Binding Cassette (ABC) Transporters to Insecticide in the Brown Planthopper, Nilaparvata lugens (Stål).

The ATP-binding cassette (ABC) transporter superfamily is one of the largest groups of proteins and plays a non-negligible role in phase III of the detoxification process, which is highly involved in the response of insects to environmental stress (plant secondary metabolites and insecticides). In the present study, in Nilaparvata lugens, we identified 32 ABC transporters, which are grouped into eight subfamilies (ABCA-H) based on phylogenetic analysis. The temporal and spatial expression profiles suggested that the nymphal stages (1st-5th) and adult males showed similarity, which was different from eggs and adult females, and NlABCA1, NlABCA2, NlABCB6, NlABCD2, NlABCG4, NlABCG12, NlABCG15, and NlABCH1 were highly expressed in the midgut and Malpighian tubules. In addition, ABCG12, which belongs to the ABC transporter G subfamily, was significantly upregulated after exposure to sulfoxaflor, nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. Moreover, verapamil significantly increased the sensitivity of N. lugens to nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. These results provide a basis for further research on ABC transporters involved in detoxification in N. lugens, and for a more comprehensive understanding of the response of N. lugens to environmental stress.

Optimization of a Binary Concrete Crack Self-Healing System Containing Bacteria and Oxygen.

An optimized strategy for the enhancement of microbially induced calcium precipitation including spore viability ensurance, nutrient selection and O2 supply was developed. Firstly, an optimal yeast extract concentration of 5 g/l in sporulation medium was determined based on viable spore yield and spore viability. Furthermore, the effects of certain influential factors on microbial calcium precipitation process of H4 in the presence of oxygen releasing tablet (ORT) were evaluated. The results showed that CaO2 is preferable to other peroxides in improving the calcium precipitation by H4. H4 strain is able to precipitate a highly insoluble calcium at the CaO2 dosage range of 7.5-12.5 g/l, and the most suitable spore concentration is 6 × 108 spores/ml when the spore viability (viable spore ratio) is approximately 50%. Lactate is the best carbon source and nitrate is the best nitrogen source for aerobic incubation. This work has laid a foundation of ternary self-healing system containing bacteria, ORT, and nutrients, which will be promising for the self-healing of cracks deep inside the concrete structure.