A symbiotic bacterium regulates the detoxification metabolism of deltamethrin in Aedes albopictus. - Related Documents




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672401.0000A symbiotic bacterium regulates the detoxification metabolism of deltamethrin in Aedes albopictus. The mosquito Aedes albopictus is an important vector of dengue, chikungunya, and Zika; and is a globally distributed invasive mosquito with increasing resistance to insecticides, thereby posing a serious risk to global public health. Symbiotic gut bacteria have been shown to be related to insecticide resistance, but knowledge is still limited for A. albopictus. Here, we explored the role of Serratia marcescens, a gut symbiotic bacterium, in the resistance of A. albopictus to the insecticide deltamethrin. Using 16S-rRNA sequencing we found that S. marcescens was significantly enriched in A. albopictus after deltamethrin exposure, and that resistance increased after S. marcescens enrichment. The enzymatic activities of mixed-function oxidase (MFO) and glutathione S-transferase (GST), two important detoxification enzymes, were higher in the bacteria-enriched mosquitoes. The expressions of ABCG4 and GSTD1, two genes related to detoxification metabolism, were up-regulated following S. marcescens infection and after deltamethrin exposure, as assayed using RNA-seq. The up-regulation of these two genes was most significant in midgut and Malpighian tubules. Our results suggest that S. marcescens infection could enhance deltamethrin resistance in A. albopictus by increasing detoxification metabolism; of interest for designing more efficient mosquito control measures.202540500053
672610.9995A symbiotic gut bacterium enhances Aedes albopictus resistance to insecticide. BACKGROUND: The increasing insecticide resistance of Aedes albopictus puts many countries in Asia and Africa, including China, at great risk of a mosquito-borne virus epidemic. To date, a growing number of researches have focused on the relationship between intestinal symbiotic bacteria and their hosts' resistance to insecticides. This provides a novel aspect to the study of resistant mechanisms. METHODS/FINDINGS: This study reveals significant composition and dynamic changes in the intestinal symbiotic bacteria of Ae. albopictus between the resistant and susceptible strains based on full-length sequencing technology. The relative abundance of Serratia oryzae was significantly higher in the resistance strain than in the susceptible strains; also, the relative abundance of S. oryzae was significantly higher in deltamethrin-induced Ae. albopictus than in their counterpart. These suggested that S. oryzae may be involved in the development of insecticide resistance in Ae. albopictus. To explore the insecticide resistance mechanism, adult mosquitoes were fed with GFP-tagged S. oryzae, which resulted in stable bacterial enrichment in the mosquito gut without affecting the normal physiology, longevity, oviposition, and hatching rates of the host. The resistance measurements were made based on bioassays as per the WHO guidelines. The results showed that the survival rate of S. oryzae-enriched Ae. albopictus was significantly higher than the untreated mosquitoes, indicating the enhanced resistance of S. oryzae-enriched Ae. albopictus. Also, the activities of three metabolic detoxification enzymes in S. oryzae-enriched mosquitoes were increased to varying degrees. Meanwhile, the activity of extracellular enzymes released by S. oryzae was measured, but only carboxylesterase activity was detected. HPLC and UHPLC were respectively used to measure deltamethrin residue concentration and metabolite qualitative analysis, showing that the deltamethrin degradation efficiency of S. oryzae was positively correlated with time and bacterial amount. Deltamethrin was broken down into 1-Oleoyl-2-hydroxy-sn-glycero-3-PE and 2',2'-Dibromo-2'-deoxyguanosine. Transcriptome analysis revealed that 9 cytochrome P450s, 8 GSTs and 7 CarEs genes were significantly upregulated. CONCLUSIONS: S. oryzae can be accumulated into adult Ae. albopictus by artificial feeding, which enhances deltamethrin resistance by inducing the metabolic detoxification genes and autocrine metabolic enzymes. S. oryzae is vertically transmitted in Ae. albopictus population. Importantly, S. oryzae can degrade deltamethrin in vitro, and use deltamethrin as the sole carbon source for their growths. Therefore, in the future, S. oryzae may also be commercially used to break down the residual insecticides in the farmland and lakes to protect the environment.202235245311
672720.9992Differences in the intestinal microbiota between insecticide-resistant and -sensitive Aedes albopictus based on full-length 16S rRNA sequencing. The intestinal symbiotic bacteria of Aedes albopictus play a potential role in host resistance to insecticides. In this study, we sequenced the full-length of 16S rRNA and analyzed the differences in the intestinal microbiota between deltamethrin-resistant and -sensitive Ae. albopictus. Symbiotic bacteria were cultured and analyzed using six types of culture media in aerobic and anaerobic environments. We found significant differences in the diversity and abundance of the intestinal microbiota of the two strains of Ae. albopictus. The symbiotic bacteria cultured in vitro were found to be mainly facultative anaerobes. The cultured bacteria such as Serratia oryzae and Acinetobacter junii may function to promote the development of insecticide resistance. This work indicates that intestinal bacteria may contribute to the enhancement of insecticide resistance of Ae. albopictus It also highlights the analytical advantage of full-length 16S rRNA sequencing to study the intestinal microbiota of mosquitoes.202133970535
832030.9991Immuno-physiological adaptations confer wax moth Galleria mellonella resistance to Bacillus thuringiensis. Microevolutionary mechanisms of resistance to a bacterial pathogen were explored in a population of the Greater wax moth, Galleria mellonella, selected for an 8.8-fold increased resistance against the entomopathogenic bacterium Bacillus thuringiensis (Bt) compared with a non-selected (suspectible) line. Defense strategies of the resistant and susceptible insect lines were compared to uncover mechanisms underpinning resistance, and the possible cost of those survival strategies. In the uninfected state, resistant insects exhibited enhanced basal expression of genes related to regeneration and amelioration of Bt toxin activity in the midgut. In addition, these insects also exhibited elevated activity of genes linked to inflammation/stress management and immune defense in the fat body. Following oral infection with Bt, the expression of these genes was further elevated in the fat body and midgut of both lines and to a greater extent some of them in resistant line than the susceptible line. This gene expression analysis reveals a pattern of resistance mechanisms targeted to sites damaged by Bt with the insect placing greater emphasis on tissue repair as revealed by elevated expression of these genes in both the fat body and midgut epithelium. Unlike the susceptible insects, Bt infection significantly reduced the diversity and richness (abundance) of the gut microbiota in the resistant insects. These observations suggest that the resistant line not only has a more intact midgut but is secreting antimicrobial factors into the gut lumen which not only mitigate Bt activity but also affects the viability of other gut bacteria. Remarkably the resistant line employs multifactorial adaptations for resistance to Bt without any detected negative trade off since the insects exhibited higher fecundity.201627029421
900740.9991Genes involved in copper resistance influence survival of Pseudomonas aeruginosa on copper surfaces. AIMS: To evaluate the killing of Pseudomonas aeruginosa PAO1 on copper cast alloys and the influence of genes on survival on copper containing medium and surfaces. METHODS AND RESULTS: Different strains of P. aeruginosa were inoculated on copper containing medium or different copper cast alloys and the survival rate determined. The survival rates were compared with rates on copper-free medium and stainless steel as control. In addition, the effect of temperature on survival was examined. CONCLUSIONS: Copper cast alloys had been previously shown to be bactericidal to various bacteria, but the mechanism of copper-mediated killing is still not known. In this report, we demonstrate that P. aeruginosa PAO1 is rapidly killed on different copper cast alloys and that genes involved in conferring copper resistance in copper-containing medium also influenced survival on copper cast alloys. We also show that the rate of killing is influenced by temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: To use copper surfaces more widely as bactericidal agents in various settings, it is important to understand how genes influence survival on these surfaces. Here we show that genes shown to be involved in copper resistance in P. aeruginosa PAO1 can have an impact on the length of survival time on copper cast alloys under certain conditions. This is an important first step for evaluation of future use of copper surfaces as bactericidal agents.200919239551
829950.9991Regulatory cross-talk supports resistance to Zn intoxication in Streptococcus. Metals such as copper (Cu) and zinc (Zn) are important trace elements that can affect bacterial cell physiology but can also intoxicate bacteria at high concentrations. Discrete genetic systems for management of Cu and Zn efflux have been described in several bacterial pathogens, including streptococci. However, insight into molecular cross-talk between systems for Cu and Zn management in bacteria that drive metal detoxification, is limited. Here, we describe a biologically consequential cross-system effect of metal management in group B Streptococcus (GBS) governed by the Cu-responsive copY regulator in response to Zn. RNAseq analysis of wild-type (WT) and copY-deficient GBS subjected to metal stress revealed unique transcriptional links between the systems for Cu and Zn detoxification. We show that the Cu-sensing role of CopY extends beyond Cu and enables CopY to regulate Cu and Zn stress responses that effect changes in gene function for central cellular processes, including riboflavin synthesis. CopY also supported GBS intracellular survival in human macrophages and virulence during disseminated infection in mice. In addition, we show a novel role for CovR in modulating GBS resistance to Zn intoxication. Identification of the Zn resistome of GBS using TraDIS revealed a suite of genes essential for GBS growth in metal stress. Several of the genes identified are novel to systems that support bacterial survival in metal stress and represent a diverse set of mechanisms that underpin microbial metal homeostasis during cell stress. Overall, this study reveals a new and important mechanism of cross-system complexity driven by CopY in bacteria to regulate cellular management of metal stress and survival.202235862444
672560.9991Honeybee (Apis mellifera) resistance to deltamethrin exposure by Modulating the gut microbiota and improving immunity. Honeybees (Apis mellifera) are important economic insects and play important roles in pollination and maintenance of ecological balance. However, the use of pesticides has posed a substantial threat to bees in recent years, with the more widely used deltamethrin being the most harmful. In this study, we found that deltamethrin exposure significantly reduced bee survival in a dose-dependent manner (p = 0.025). In addition, metagenomic sequencing further revealed that DM exposure significantly reduced the diversity of the bee gut microbiota (Chao1, p < 0.0001; Shannon, p < 0.0001; Simpson, p < 0.0001) and decreased the relative abundance of core species of the gut microbiota. Importantly, in studies of GF-bees, we found that the colonization of important gut bacteria such as Gilliamella apicola and Lactobacillus kunkeei significantly increased bee resistance to DM (survival rate increased from 16.7 to 66.7%). Interestingly, we found that the immunity-genes Defensin-2 and Toll were significantly upregulated in bees after the colonization of gut bacteria. These results suggest that gut bacteria may protect against DM stress by improving host immunity. Our findings provide an important rationale for protecting honeybees from pollutants from the perspective of gut microbes.202236208825
900170.9991Bacterial Methionine Metabolism Genes Influence Drosophila melanogaster Starvation Resistance. Animal-associated microorganisms (microbiota) dramatically influence the nutritional and physiological traits of their hosts. To expand our understanding of such influences, we predicted bacterial genes that influence a quantitative animal trait by a comparative genomic approach, and we extended these predictions via mutant analysis. We focused on Drosophila melanogaster starvation resistance (SR). We first confirmed that D. melanogaster SR responds to the microbiota by demonstrating that bacterium-free flies have greater SR than flies bearing a standard 5-species microbial community, and we extended this analysis by revealing the species-specific influences of 38 genome-sequenced bacterial species on D. melanogaster SR. A subsequent metagenome-wide association analysis predicted bacterial genes with potential influence on D. melanogaster SR, among which were significant enrichments in bacterial genes for the metabolism of sulfur-containing amino acids and B vitamins. Dietary supplementation experiments established that the addition of methionine, but not B vitamins, to the diets significantly lowered D. melanogaster SR in a way that was additive, but not interactive, with the microbiota. A direct role for bacterial methionine metabolism genes in D. melanogaster SR was subsequently confirmed by analysis of flies that were reared individually with distinct methionine cycle Escherichia coli mutants. The correlated responses of D. melanogaster SR to bacterial methionine metabolism mutants and dietary modification are consistent with the established finding that bacteria can influence fly phenotypes through dietary modification, although we do not provide explicit evidence of this conclusion. Taken together, this work reveals that D. melanogaster SR is a microbiota-responsive trait, and specific bacterial genes underlie these influences.IMPORTANCE Extending descriptive studies of animal-associated microorganisms (microbiota) to define causal mechanistic bases for their influence on animal traits is an emerging imperative. In this study, we reveal that D. melanogaster starvation resistance (SR), a model quantitative trait in animal genetics, responds to the presence and identity of the microbiota. Using a predictive analysis, we reveal that the amino acid methionine has a key influence on D. melanogaster SR and show that bacterial methionine metabolism mutants alter normal patterns of SR in flies bearing the bacteria. Our data further suggest that these effects are additive, and we propose the untested hypothesis that, similar to bacterial effects on fruit fly triacylglyceride deposition, the bacterial influence may be through dietary modification. Together, these findings expand our understanding of the bacterial genetic basis for influence on a nutritionally relevant trait of a model animal host.201829934334
74080.9991Effects of NF-kB Signaling Inhibitors on Bed Bug Resistance to Orally Provisioned Entomopathogenic Bacteria. Bed bugs are globally important pests and there is an ongoing need for the development and improvement of bed bug control tools. Though promising against other insect pests, the exploration of biological methods for bed bug control is limited. Previously, we identified several species of bacteria that have entomopathogenic effects against bed bugs when ingested. We also described the conservation of several antibacterial responses in bed bugs, including the expression of immune effector genes regulated by NF-kB transcription factors through the Toll and immune deficiency (IMD) signaling pathways. Accordingly, we predicted that chemical inhibition of NF-kB signaling could reduce bed bug resistance to orally provisioned entomopathogenic bacteria, potentially improving their effectiveness as biological control agents. In the present study, we administered four small molecule inhibitors of NF-kB signaling (BMS345541, IKK16, IMD0354, Takinib) to bed bugs by feeding them in a blood meal. We then quantified basal mortality and mortality in response to oral infection with two different entomopathogenic bacteria (Pseudomonas entomophila and Bacillus thuringiensis israelensis). None of the NF-kB signaling inhibitors tested increased mortality above control levels when administered alone, suggesting a lack of direct toxicity. However, one inhibitor (IKK16) significantly enhanced the rate of mortality from oral infection with P. entomophila. Enhanced mortality was independent of direct effects of IKK16 on P. entomophila growth in vitro but was associated with higher bacterial loads in vivo (i.e., reduced resistance). Together, these results provide new insight into the regulation of the bed bug immune system and suggest that administration of entomopathogens in combination with inhibition of immune signaling pathways to reduce infection resistance may be effective for biological control of bed bugs.202133808065
886890.9990Effects of Stress, Reactive Oxygen Species, and the SOS Response on De Novo Acquisition of Antibiotic Resistance in Escherichia coli. Strategies to prevent the development of antibiotic resistance in bacteria are needed to reduce the threat of infectious diseases to human health. The de novo acquisition of resistance due to mutations and/or phenotypic adaptation occurs rapidly as a result of interactions of gene expression and mutations (N. Handel, J. M. Schuurmans, Y. Feng, S. Brul, and B. H. Ter Kuile, Antimicrob Agents Chemother 58:4371-4379, 2014, http://dx.doi.org/10.1128/AAC.02892-14). In this study, the contribution of several individual genes to the de novo acquisition of antibiotic resistance in Escherichia coli was investigated using mutants with deletions of genes known to be involved in antibiotic resistance. The results indicate that recA, vital for the SOS response, plays a crucial role in the development of antibiotic resistance. Likewise, deletion of global transcriptional regulators, such as gadE or soxS, involved in pH homeostasis and superoxide removal, respectively, can slow the acquisition of resistance to a degree depending on the antibiotic. Deletion of the transcriptional regulator soxS, involved in superoxide removal, slowed the acquisition of resistance to enrofloxacin. Acquisition of resistance occurred at a lower rate in the presence of a second stress factor, such as a lowered pH or increased salt concentration, than in the presence of optimal growth conditions. The overall outcome suggests that a central cellular mechanism is crucial for the development of resistance and that genes involved in the regulation of transcription play an essential role. The actual cellular response, however, depends on the class of antibiotic in combination with environmental conditions.201526666928
8867100.9990Hfq plays important roles in virulence and stress adaptation in Cronobacter sakazakii ATCC 29544. Cronobacter spp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated with Cronobacter infection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq in C. sakazakii virulence. In the absence of hfq, C. sakazakii was highly attenuated in dissemination in vivo, showed defects in invasion (3-fold) into animal cells and survival (10(3)-fold) within host cells, and exhibited low resistance to hydrogen peroxide (10(2)-fold). Remarkably, the loss of hfq led to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lacking hfq. Together, these data strongly suggest that hfq plays important roles in the virulence of C. sakazakii by participating in the regulation of multiple genes.201525754196
685110.9990Implication of a Key Region of Six Bacillus cereus Genes Involved in Siroheme Synthesis, Nitrite Reductase Production and Iron Cluster Repair in the Bacterial Response to Nitric Oxide Stress. Bacterial response to nitric oxide (NO) is of major importance for bacterial survival. NO stress is a main actor of the eukaryotic immune response and several pathogenic bacteria have developed means for detoxification and repair of the damages caused by NO. However, bacterial mechanisms of NO resistance by Gram-positive bacteria are poorly described. In the opportunistic foodborne pathogen Bacillus cereus, genome sequence analyses did not identify homologs to known NO reductases and transcriptional regulators, such as NsrR, which orchestrate the response to NO of other pathogenic or non-pathogenic bacteria. Using a transcriptomic approach, we investigated the adaptation of B. cereus to NO stress. A cluster of 6 genes was identified to be strongly up-regulated in the early phase of the response. This cluster contains an iron-sulfur cluster repair enzyme, a nitrite reductase and three enzymes involved in siroheme biosynthesis. The expression pattern and close genetic localization suggest a functional link between these genes, which may play a pivotal role in the resistance of B. cereus to NO stress during infection.202134064887
169120.9990Heavy metal resistance in Cupriavidus metallidurans CH34 is governed by an intricate transcriptional network. The soil bacterium Cupriavidus metallidurans CH34 contains a high number of heavy metal resistance genes making it an interesting model organism to study microbial responses to heavy metals. In this study the transcriptional response of strain CH34 was measured when challenged to sub-lethal concentrations of various essential or toxic metals. Based on the global transcriptional responses for each challenge and the overlap in upregulated genes between different metal responses, the sixteen metals were clustered in three groups. In addition, the transcriptional response of already known metal resistance genes was assessed, and new metal response gene clusters were identified. The majority of the studied metal response loci showed similar expression profiles when cells were exposed to different metals, suggesting complex interplay at transcriptional level between the different metal responses. The pronounced redundancy of these metal resistant regions-as illustrated by the large number of paralogous genes-combined with the phylogenetic distribution of these metal response regions within either evolutionary related or other metal resistant bacteria, provides important insights on the recent evolutionary forces shaping this naturally soil-dwelling bacterium into a highly metal-resistant strain well adapted to harsh and anthropogenic environments.201121706166
8414130.9990Patterns of Piscirickettsia salmonis load in susceptible and resistant families of Salmo salar. The pathogen Piscirickettsia salmonis produces a systemic aggressive infection that involves several organs and tissues in salmonids. In spite of the great economic losses caused by this pathogen in the Atlantic salmon (Salmo salar) industry, very little is known about the resistance mechanisms of the host to this pathogen. In this paper, for the first time, we aimed to identify the bacterial load in head kidney and muscle of Atlantic salmon exhibiting differential familiar mortality. Furthermore, in order to assess the patterns of gene expression of immune related genes in susceptible and resistant families, a set of candidate genes was evaluated using deep sequencing of the transcriptome. The results showed that the bacterial load was significantly lower in resistant fish, when compared with the susceptible individuals. Based on the candidate genes analysis, we infer that the resistant hosts triggered up-regulation of specific genes (such as for example the LysC), which may explain a decrease in the bacterial load in head kidney, while the susceptible fish presented an exacerbated innate response, which is unable to exert an effective response against the bacteria. Interestingly, we found a higher bacterial load in muscle when compared with head kidney. We argue that this is possible due to the availability of an additional source of iron in muscle. Besides, the results show that the resistant fish could not be a likely reservoir of the bacteria.201525862974
8699140.9990Hordeum vulgare differentiates its response to beneficial bacteria. BACKGROUND: In nature, beneficial bacteria triggering induced systemic resistance (ISR) may protect plants from potential diseases, reducing yield losses caused by diverse pathogens. However, little is known about how the host plant initially responds to different beneficial bacteria. To reveal the impact of different bacteria on barley (Hordeum vulgare), bacterial colonization patterns, gene expression, and composition of seed endophytes were explored. RESULTS: This study used the soil-borne Ensifer meliloti, as well as Pantoea sp. and Pseudomonas sp. isolated from barley seeds, individually. The results demonstrated that those bacteria persisted in the rhizosphere but with different colonization patterns. Although root-leaf translocation was not observed, all three bacteria induced systemic resistance (ISR) against foliar fungal pathogens. Transcriptome analysis revealed that ion- and stress-related genes were regulated in plants that first encountered bacteria. Iron homeostasis and heat stress responses were involved in the response to E. meliloti and Pantoea sp., even if the iron content was not altered. Heat shock protein-encoding genes responded to inoculation with Pantoea sp. and Pseudomonas sp. Furthermore, bacterial inoculation affected the composition of seed endophytes. Investigation of the following generation indicated that the enhanced resistance was not heritable. CONCLUSIONS: Here, using barley as a model, we highlighted different responses to three different beneficial bacteria as well as the influence of soil-borne Ensifer meliloti on the seed microbiome. In total, these results can help to understand the interaction between ISR-triggering bacteria and a crop plant, which is essential for the application of biological agents in sustainable agriculture.202337789272
8304150.9990A Shift to Human Body Temperature (37°C) Rapidly Reprograms Multiple Adaptive Responses in Escherichia coli That Would Facilitate Niche Survival and Colonization. One of the first environmental cues sensed by a microbe as it enters a human host is an upshift in temperature to 37°C. In this dynamic time point analysis, we demonstrate that this environmental transition rapidly signals a multitude of gene expression changes in Escherichia coli. Bacteria grown at 23°C under aerobic conditions were shifted to 37°C, and mRNA expression was measured at time points after the shift to 37°C (t = 0.5, 1, and 4 h). The first hour is characterized by a transient shift to anaerobic respiration strategies and stress responses, particularly acid resistance, indicating that temperature serves as a sentinel cue to predict and prepare for various niches within the host. The temperature effects on a subset of stress response genes were shown to be mediated by RpoS and directly correlated with RpoS, DsrA, and RprA levels, and increased acid resistance was observed that was dependent on 23°C growth and RpoS. By 4 h, gene expression shifted to aerobic respiration pathways and decreased stress responses, coupled with increases in genes associated with biosynthesis (amino acid and nucleotides), iron uptake, and host defense. ompT, a gene that confers resistance to antimicrobial peptides, was highly thermoregulated, with a pattern conserved in enteropathogenic and uropathogenic E. coli strains. An immediate decrease in curli gene expression concomitant with an increase in flagellar gene expression implicates temperature in this developmental decision. Together, our studies demonstrate that temperature signals a reprogramming of gene expression immediately upon an upshift that may predict, prepare, and benefit the survival of the bacterium within the host. IMPORTANCE As one of the first cues sensed by the microbe upon entry into a human host, understanding how bacteria like E. coli modulate gene expression in response to temperature improves our understanding of how bacteria immediately initiate responses beneficial for survival and colonization. For pathogens, understanding the various pathways of thermal regulation could yield valuable targets for anti-infective chemotherapeutic drugs or disinfection measures. In addition, our data provide a dynamic examination of the RpoS stress response, providing genome-wide support for how temperature impacts RpoS through changes in RpoS stability and modulation by small regulatory RNAs.202134516284
8995160.9990Interaction between mutations and regulation of gene expression during development of de novo antibiotic resistance. Bacteria can become resistant not only by horizontal gene transfer or other forms of exchange of genetic information but also by de novo by adaptation at the gene expression level and through DNA mutations. The interrelationship between changes in gene expression and DNA mutations during acquisition of resistance is not well documented. In addition, it is not known whether the DNA mutations leading to resistance always occur in the same order and whether the final result is always identical. The expression of >4,000 genes in Escherichia coli was compared upon adaptation to amoxicillin, tetracycline, and enrofloxacin. During adaptation, known resistance genes were sequenced for mutations that cause resistance. The order of mutations varied within two sets of strains adapted in parallel to amoxicillin and enrofloxacin, respectively, whereas the buildup of resistance was very similar. No specific mutations were related to the rather modest increase in tetracycline resistance. Ribosome-sensed induction and efflux pump activation initially protected the cell through induction of expression and allowed it to survive low levels of antibiotics. Subsequently, mutations were promoted by the stress-induced SOS response that stimulated modulation of genetic instability, and these mutations resulted in resistance to even higher antibiotic concentrations. The initial adaptation at the expression level enabled a subsequent trial and error search for the optimal mutations. The quantitative adjustment of cellular processes at different levels accelerated the acquisition of antibiotic resistance.201424841263
6723170.9990Gut Microbiota Mediate Insecticide Resistance in the Diamondback Moth, Plutella xylostella (L.). The development of insecticide resistance in insect pests is a worldwide concern and elucidating the underlying mechanisms is critical for effective crop protection. Recent studies have indicated potential links between insect gut microbiota and insecticide resistance and these may apply to the diamondback moth, Plutella xylostella (L.), a globally and economically important pest of cruciferous crops. We isolated Enterococcus sp. (Firmicutes), Enterobacter sp. (Proteobacteria), and Serratia sp. (Proteobacteria) from the guts of P. xylostella and analyzed the effects on, and underlying mechanisms of insecticide resistance. Enterococcus sp. enhanced resistance to the widely used insecticide, chlorpyrifos, in P. xylostella, while in contrast, Serratia sp. decreased resistance and Enterobacter sp. and all strains of heat-killed bacteria had no effect. Importantly, the direct degradation of chlorpyrifos in vitro was consistent among the three strains of bacteria. We found that Enterococcus sp., vitamin C, and acetylsalicylic acid enhanced insecticide resistance in P. xylostella and had similar effects on expression of P. xylostella antimicrobial peptides. Expression of cecropin was down-regulated by the two compounds, while gloverin was up-regulated. Bacteria that were not associated with insecticide resistance induced contrasting gene expression profiles to Enterococcus sp. and the compounds. Our studies confirmed that gut bacteria play an important role in P. xylostella insecticide resistance, but the main mechanism is not direct detoxification of insecticides by gut bacteria. We also suggest that the influence of gut bacteria on insecticide resistance may depend on effects on the immune system. Our work advances understanding of the evolution of insecticide resistance in this key pest and highlights directions for research into insecticide resistance in other insect pest species.201829410659
8298180.9990Cellular Management of Zinc in Group B Streptococcus Supports Bacterial Resistance against Metal Intoxication and Promotes Disseminated Infection. Zinc is an essential trace element for normal bacterial physiology but, divergently, can intoxicate bacteria at high concentrations. Here, we define the molecular systems for Zn detoxification in Streptococcus agalactiae, also known as group B streptococcus, and examine the effects of resistance to Zn stress on virulence. We compared the growth of wild-type bacteria and mutants deleted for the Zn exporter, czcD, and the response regulator, sczA, using Zn-stress conditions in vitro Macrophage antibiotic protection assays and a mouse model of disseminated infection were used to assess virulence. Global bacterial transcriptional responses to Zn stress were defined by RNA sequencing and quantitative reverse transcription-PCR. czcD and sczA enabled S. agalactiae to survive Zn stress, with the putative CzcD efflux system activated by SczA. Additional genes activated in response to Zn stress encompassed divalent cation transporters that contribute to regulation of Mn and Fe homeostasis. In vivo, the czcD-sczA Zn management axis supported virulence in the blood, heart, liver, and bladder. Additionally, several genes not previously linked to Zn stress in any bacterium, including, most notably, arcA for arginine deamination, also mediated resistance to Zn stress, representing a novel molecular mechanism of bacterial resistance to metal intoxication. Taken together, these findings show that S. agalactiae responds to Zn stress by sczA regulation of czcD, with additional novel mechanisms of resistance supported by arcA, encoding arginine deaminase. Cellular management of Zn stress in S. agalactiae supports virulence by facilitating bacterial survival in the host during systemic infection.IMPORTANCEStreptococcus agalactiae, also known as group B streptococcus, is an opportunistic pathogen that causes various diseases in humans and animals. This bacterium has genetic systems that enable zinc detoxification in environments of metal stress, but these systems remain largely undefined. Using a combination of genomic, genetic, and cellular assays, we show that this pathogen controls Zn export through CzcD to manage Zn stress and utilizes a system of arginine deamination never previously linked to metal stress responses in bacteria to survive metal intoxication. We show that these systems are crucial for survival of S. agalactiaein vitro during Zn stress and also enhance virulence during systemic infection in mice. These discoveries establish new molecular mechanisms of resistance to metal intoxication in bacteria; we suggest these mechanisms operate in other bacteria as a way to sustain microbial survival under conditions of metal stress, including in host environments.202134011683
8967190.9990Distinct transcriptomic response of S. coelicolor to ciprofloxacin in a nutrient-rich environment. With the rising threat of anti-microbial resistance (AMR), there is an urgent need to enhance efficacy of existing antibiotics. Understanding the myriad mechanisms through which bacteria evade these drugs would be of immense value to designing novel strategies against them. Streptomyces coelicolor A3(2) M145 belongs to the actinomyctes species that are responsible for more than two-thirds of antibiotics. This group of bacteria therefore encodes for various mechanisms that can resist both endogenous and non-endogenous antibiotics. In an earlier study, we had studied the transcriptomic response of these bacteria to ciprofloxacin, when cultured in a minimal media. In this work, we investigate why the minimum inhibitory concentration of the drug increases by fourfold when the bacteria are grown in a nutrient-rich media. Through transcriptomic, biochemical, and microscopic studies, we show that S. coelicolor responds to ciprofloxacin in a concentration-dependent manner. While, sub-inhibitory concentration of the drug primarily causes oxidative stress, the inhibitory concentration of ciprofloxacin evokes a more severe genome-wide response in the cell, which ranges from the familiar upregulation of the SOS response and DNA repair pathways to the widespread alterations in the central metabolism pathway to accommodate the increased needs of nucleotides and other precursors. Further, the upregulation of peptidoglycan synthesis genes, along with microscopy images, suggest alterations in the cell morphology to increase fitness of the bacteria during the antibiotic stress. The data also points to the enhanced efflux activity in cells cultured in rich media that contributes significantly towards reducing intracellular drug concentration and thus promotes survival.201830327831