RESISTOMICS - Word Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
813300.9062Symbiotic bacteria confer insecticide resistance by metabolizing buprofezin in the brown planthopper, Nilaparvata lugens (Stål). Buprofezin, a chitin synthesis inhibitor, is widely used to control several economically important insect crop pests. However, the overuse of buprofezin has led to the evolution of resistance and exposed off-target organisms present in agri-environments to this compound. As many as six different strains of bacteria isolated from these environments have been shown to degrade buprofezin. However, whether insects can acquire these buprofezin-degrading bacteria from soil and enhance their own resistance to buprofezin remains unknown. Here we show that field strains of the brown planthopper, Nilaparvata lugens, have acquired a symbiotic bacteria, occurring naturally in soil and water, that provides them with resistance to buprofezin. We isolated a symbiotic bacterium, Serratia marcescens (Bup_Serratia), from buprofezin-resistant N. lugens and showed it has the capacity to degrade buprofezin. Buprofezin-susceptible N. lugens inoculated with Bup_Serratia became resistant to buprofezin, while antibiotic-treated N. lugens became susceptible to this insecticide, confirming the important role of Bup_Serratia in resistance. Sequencing of the Bup_Serratia genome identified a suite of candidate genes involved in the degradation of buprofezin, that were upregulated upon exposure to buprofezin. Our findings demonstrate that S. marcescens, an opportunistic pathogen of humans, can metabolize the insecticide buprofezin and form a mutualistic relationship with N. lugens to enhance host resistance to buprofezin. These results provide new insight into the mechanisms underlying insecticide resistance and the interactions between bacteria, insects and insecticides in the environment. From an applied perspective they also have implications for the control of highly damaging crop pests.202338091367
847210.9053Genetic architecture of resistance to plant secondary metabolites in Photorhabdus entomopathogenic bacteria. BACKGROUND: Entomopathogenic nematodes of the genus Heterorhabditis establish a symbiotic association with Photorhabdus bacteria. Together, they colonize and rapidly kill insects, making them important biological control agents against agricultural pests. Improving their biocontrol traits by engineering resistance to plant secondary metabolites (benzoxazinoids) in Photorhabdus symbiotic bacteria through experimental evolution has been shown to increase their lethality towards benzoxazinoid-defended larvae of the western corn rootworm, a serious crop pest of maize, and it is therefore a promising approach to develop more efficient biocontrol agents to manage this pest. To enhance our understanding of the genetic bases of benzoxazinoid resistance in Photorhabdus bacteria, we conducted an experimental evolution experiment with a phylogenetically diverse collection of Photorhabdus strains from different geographic origins. We cultured 27 different strains in medium containing 6-methoxy-2-benzoxazolinone (MBOA), a highly active benzoxazinoid breakdown product, for 35 24 h-cycles to select for benzoxazinoid-resistant strains. Then, we carried out genome-wide sequence comparisons to uncover the genetic alterations associated with benzoxazinoid resistance. Lastly, we evaluated the resistance of the newly isolated resistant Photorhabdus strains to eight additional bioactive compounds, including 2-benzoxazolinone (BOA), nicotine, caffeine, 6-chloroacetyl-2-benzoxazolinone (CABOA), digitoxin, fenitrothion, ampicillin, and kanamycin. RESULTS: We found that benzoxazinoid resistance evolves rapidly in Photorhabdus in a strain-specific manner. Across the different Photorhabdus strains, a total of nineteen nonsynonymous point mutations, two stop codon gains, and one frameshift were associated with higher benzoxazinoid resistance. The different genetic alterations were polygenic and occurred in genes coding for the EnvZ/OmpR two-component regulatory system, the different subunits of the DNA-directed RNA polymerase, and the AcrABZ-TolC multidrug efflux pump. Apart from increasing MBOA resistance, the different mutations were also associated with cross-resistance to 2-benzoxazolinone (BOA), nicotine, caffeine, and 6-chloroacetyl-2-benzoxazolinone (CABOA) and with collateral sensitivity to fenitrothion, ampicillin, and kanamycin. Targeted mutagenesis will provide a deeper mechanistic understanding, including the relative contribution of the different mutation types. CONCLUSIONS: Our study reveals several genomic features that are associated with resistance to xenobiotics in this important group of biological control agents and enhances the availability of molecular tools to develop better biological control agents, which is essential for more sustainable and ecologically friendly agricultural practices.202541168779
439820.9050Shared and Unique Evolutionary Trajectories to Ciprofloxacin Resistance in Gram-Negative Bacterial Pathogens. Resistance to the broad-spectrum antibiotic ciprofloxacin is detected at high rates for a wide range of bacterial pathogens. To investigate the dynamics of ciprofloxacin resistance development, we applied a comparative resistomics workflow for three clinically relevant species of Gram-negative bacteria: Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa. We combined experimental evolution in a morbidostat with deep sequencing of evolving bacterial populations in time series to reveal both shared and unique aspects of evolutionary trajectories. Representative clone characterization by sequencing and MIC measurements enabled direct assessment of the impact of mutations on the extent of acquired drug resistance. In all three species, we observed a two-stage evolution: (i) early ciprofloxacin resistance reaching 4- to 16-fold the MIC for the wild type, commonly as a result of single mutations in DNA gyrase target genes (gyrA or gyrB), and (ii) additional genetic alterations affecting the transcriptional control of the drug efflux machinery or secondary target genes (DNA topoisomerase parC or parE). IMPORTANCE The challenge of spreading antibiotic resistance calls for systematic efforts to develop more "irresistible" drugs based on a deeper understanding of dynamics and mechanisms of antibiotic resistance acquisition. To address this challenge, we have established a comparative resistomics approach which combines experimental evolution in a continuous-culturing device, the morbidostat, with ultradeep sequencing of evolving microbial populations to identify evolutionary trajectories (mutations and genome rearrangements) leading to antibiotic resistance over a range of target pathogens. Here, we report the comparative resistomics study of three Gram-negative bacteria (Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa), which revealed shared and species-specific aspects of the evolutionary landscape leading to robust resistance against the clinically important antibiotic ciprofloxacin. Despite some differences between morbidostat-deduced mutation profiles and those observed in clinical isolates of individual species, a cross-species comparative resistomics approach allowed us to recapitulate all types of clinically relevant ciprofloxacin resistance mechanisms. This observation supports the anticipated utility of this approach in guiding rational optimization of treatment regimens for current antibiotics and the development of novel antibiotics with minimized resistance propensities.202134154405
56230.9049Macrolones target bacterial ribosomes and DNA gyrase and can evade resistance mechanisms. Growing resistance toward ribosome-targeting macrolide antibiotics has limited their clinical utility and urged the search for superior compounds. Macrolones are synthetic macrolide derivatives with a quinolone side chain, structurally similar to DNA topoisomerase-targeting fluoroquinolones. While macrolones show enhanced activity, their modes of action have remained unknown. Here, we present the first structures of ribosome-bound macrolones, showing that the macrolide part occupies the macrolide-binding site in the ribosomal exit tunnel, whereas the quinolone moiety establishes new interactions with the tunnel. Macrolones efficiently inhibit both the ribosome and DNA topoisomerase in vitro. However, in the cell, they target either the ribosome or DNA gyrase or concurrently both of them. In contrast to macrolide or fluoroquinolone antibiotics alone, dual-targeting macrolones are less prone to select resistant bacteria carrying target-site mutations or to activate inducible macrolide resistance genes. Furthermore, because some macrolones engage Erm-modified ribosomes, they retain activity even against strains with constitutive erm resistance genes.202439039256
74840.9048Contact-dependent growth inhibition toxins exploit multiple independent cell-entry pathways. Contact-dependent growth inhibition (CDI) systems function to deliver toxins into neighboring bacterial cells. CDI+ bacteria export filamentous CdiA effector proteins, which extend from the inhibitor-cell surface to interact with receptors on neighboring target bacteria. Upon binding its receptor, CdiA delivers a toxin derived from its C-terminal region. CdiA C-terminal (CdiA-CT) sequences are highly variable between bacteria, reflecting the multitude of CDI toxin activities. Here, we show that several CdiA-CT regions are composed of two domains, each with a distinct function during CDI. The C-terminal domain typically possesses toxic nuclease activity, whereas the N-terminal domain appears to control toxin transport into target bacteria. Using genetic approaches, we identified ptsG, metI, rbsC, gltK/gltJ, yciB, and ftsH mutations that confer resistance to specific CdiA-CTs. The resistance mutations all disrupt expression of inner-membrane proteins, suggesting that these proteins are exploited for toxin entry into target cells. Moreover, each mutation only protects against inhibition by a subset of CdiA-CTs that share similar N-terminal domains. We propose that, following delivery of CdiA-CTs into the periplasm, the N-terminal domains bind specific inner-membrane receptors for subsequent translocation into the cytoplasm. In accord with this model, we find that CDI nuclease domains are modular payloads that can be redirected through different import pathways when fused to heterologous N-terminal "translocation domains." These results highlight the plasticity of CDI toxin delivery and suggest that the underlying translocation mechanisms could be harnessed to deliver other antimicrobial agents into Gram-negative bacteria.201526305955
902750.9047Scorpion Venom Antimicrobial Peptides Induce Siderophore Biosynthesis and Oxidative Stress Responses in Escherichia coli. The increasing development of microbial resistance to classical antimicrobial agents has led to the search for novel antimicrobials. Antimicrobial peptides (AMPs) derived from scorpion and snake venoms offer an attractive source for the development of novel therapeutics. Smp24 (24 amino acids [aa]) and Smp43 (43 aa) are broad-spectrum AMPs that have been identified from the venom gland of the Egyptian scorpion Scorpio mauruspalmatus and subsequently characterized. Using a DNA microarray approach, we examined the transcriptomic responses of Escherichia coli to subinhibitory concentrations of Smp24 and Smp43 peptides following 5 h of incubation. Seventy-two genes were downregulated by Smp24, and 79 genes were downregulated by Smp43. Of these genes, 14 genes were downregulated in common and were associated with bacterial respiration. Fifty-two genes were specifically upregulated by Smp24. These genes were predominantly related to cation transport, particularly iron transport. Three diverse genes were independently upregulated by Smp43. Strains with knockouts of differentially regulated genes were screened to assess the effect on susceptibility to Smp peptides. Ten mutants in the knockout library had increased levels of resistance to Smp24. These genes were predominantly associated with cation transport and binding. Two mutants increased resistance to Smp43. There was no cross-resistance in mutants resistant to Smp24 or Smp43. Five mutants showed increased susceptibility to Smp24, and seven mutants showed increased susceptibility to Smp43. Of these mutants, formate dehydrogenase knockout (fdnG) resulted in increased susceptibility to both peptides. While the electrostatic association between pore-forming AMPs and bacterial membranes followed by integration of the peptide into the membrane is the initial starting point, it is clear that there are numerous subsequent additional intracellular mechanisms that contribute to their overall antimicrobial effect.IMPORTANCE The development of life-threatening resistance of pathogenic bacteria to the antibiotics typically in use in hospitals and the community today has led to an urgent need to discover novel antimicrobial agents with different mechanisms of action. As an ancient host defense mechanism of the innate immune system, antimicrobial peptides (AMPs) are attractive candidates to fill that role. Scorpion venoms have proven to be a rich source of AMPs. Smp24 and Smp43 are new AMPs that have been identified from the venom gland of the Egyptian scorpion Scorpio maurus palmatus, and these peptides can kill a wide range of bacterial pathogens. By better understanding how these AMPs affect bacterial cells, we can modify their structure to make better drugs in the future.202133980680
80660.9046A two-component small multidrug resistance pump functions as a metabolic valve during nicotine catabolism by Arthrobacter nicotinovorans. The genes nepAB of a small multidrug resistance (SMR) pump were identified as part of the pAO1-encoded nicotine regulon responsible for nicotine catabolism in Arthrobacter nicotinovorans. When [(14)C]nicotine was added to the growth medium the bacteria exported the (14)C-labelled end product of nicotine catabolism, methylamine. In the presence of the proton-motive force inhibitors 2,4-dinitrophenol (DNP), carbonyl cyanide m-chlorophenylhydrazone (CCCP) or the proton ionophore nigericin, export of methylamine was inhibited and radioactivity accumulated inside the bacteria. Efflux of [(14)C]nicotine-derived radioactivity from bacteria was also inhibited in a pmfR : cmx strain with downregulated nepAB expression. Because of low amine oxidase levels in the pmfR : cmx strain, gamma-N-methylaminobutyrate, the methylamine precursor, accumulated. Complementation of this strain with the nepAB genes, carried on a plasmid, restored the efflux of nicotine breakdown products. Both NepA and NepB were required for full export activity, indicating that they form a two-component efflux pump. NepAB may function as a metabolic valve by exporting methylamine, the end product of nicotine catabolism, and, in conditions under which it accumulates, the intermediate gamma-N-methylaminobutyrate.200717464069
843170.9044A quaternary ammonium salt grafted tannin-based flocculant boosts the conjugative transfer of plasmid-born antibiotic resistance genes: The nonnegligible side of their flocculation-sterilization properties. This study developed dual-function tannin-based flocculants, namely tannin-graft-acrylamide-diallyl dimethyl ammonium chloride (TGCC-A/TGCC-C), endowed with enhanced flocculation-sterilization properties. The impacts of these flocculants on proliferation and transformation of antibiotic resistance genes (ARGs) among bacteria during the flocculation-deposition process were examined. TGCC-A/TGCC-C exhibited remarkable flocculation capacities towards both Escherichia coli and Staphylococcus aureus, encompassing a logarithmic range of initial cell density (10(8)-10(9) CFU/mL) and a broad pH spectrum (pH 2-11). The grafted quaternary ammonium salt groups played pivotal parts in flocculation through charge neutralization and bridging mechanisms, concurrently contributing to sterilization by disrupting cellular membranes. The correlation between flocculation and sterilization entails a sequential progression, where an excess of TGCC, initially employed for flocculation, is subsequently consumed for sterilization purposes. The frequencies of ARGs conjugative transfer were enhanced in bacterial flocs across all TGCC treatments, stemming from augmented bacterial aggregation and cell membrane permeability, elicited stress response, and up-regulated genes encoding plasmid transfer. These findings underscore the indispensable role of flocculation-sterilization effects in mediating the propagation of ARGs, consequently providing substantial support for the scientific evaluation of the environmental risks associated with flocculants in the context of ARGs dissemination during the treatment of raw water featuring high bacterial density.202337619725
62180.9043Activation of ChvG-ChvI regulon by cell wall stress confers resistance to β-lactam antibiotics and initiates surface spreading in Agrobacterium tumefaciens. A core component of nearly all bacteria, the cell wall is an ideal target for broad spectrum antibiotics. Many bacteria have evolved strategies to sense and respond to antibiotics targeting cell wall synthesis, especially in the soil where antibiotic-producing bacteria compete with one another. Here we show that cell wall stress caused by both chemical and genetic inhibition of the essential, bifunctional penicillin-binding protein PBP1a prevents microcolony formation and activates the canonical host-invasion two-component system ChvG-ChvI in Agrobacterium tumefaciens. Using RNA-seq, we show that depletion of PBP1a for 6 hours results in a downregulation in transcription of flagellum-dependent motility genes and an upregulation in transcription of type VI secretion and succinoglycan biosynthesis genes, a hallmark of the ChvG-ChvI regulon. Depletion of PBP1a for 16 hours, results in differential expression of many additional genes and may promote a stress response, resembling those of sigma factors in other bacteria. Remarkably, the overproduction of succinoglycan causes cell spreading and deletion of the succinoglycan biosynthesis gene exoA restores microcolony formation. Treatment with cefsulodin phenocopies depletion of PBP1a and we correspondingly find that chvG and chvI mutants are hypersensitive to cefsulodin. This hypersensitivity only occurs in response to treatment with β-lactam antibiotics, suggesting that the ChvG-ChvI pathway may play a key role in resistance to antibiotics targeting cell wall synthesis. Finally, we provide evidence that ChvG-ChvI likely has a conserved role in conferring resistance to cell wall stress within the Alphaproteobacteria that is independent of the ChvG-ChvI repressor ExoR.202236480495
902690.9042Citral and its derivatives inhibit quorum sensing and biofilm formation in Chromobacterium violaceum. With an upsurge in multidrug resistant bacteria backed by biofilm defence armours, there is a desperate need of new antibiotics with a non-traditional mechanism of action. Targeting bacteria by misguiding them or halting their communication is a new approach that could offer a new way to combat the multidrug resistance problem. Quorum sensing is considered to be the achilles heel of bacteria that has a lot to offer. Since, both quorum sensing and biofilm formation have been related to drug resistance and pathogenicity, in this study we synthesised new derivatives of citral with antiquorum sensing and biofilm disrupting properties. We previously reported antimicrobial and antiquorum sensing activity of citral and herein we report the synthesis and evaluation of citral and its derivatives (CD1-CD3) for antibacterial, antibiofilm and antiquorum sensing potential against Chromobacterium violaceum using standard methods. Preliminary results revealed that CD1 is the most active of all the derivatives. Qualitative and quantitative evaluation of antiquorum sensing activity at sub-inhibitory concentrations of these compounds also revealed high activity for CD1 followed by CD2, CD3 and citral. These compounds also inhibit biofilm formation at subinhibitory concentrations without causing any bacterial growth inhibition. These results were replicated by RT-qPCR with down regulation of the quorum sensing genes when C. violaceum was treated with these test compounds. Overall, the results are quite encouraging, revealing that biofilm and quorum sensing are interrelated processes and also indicating the potential of these derivatives to impede bacterial communication and biofilm formation.202133392626
607100.9041A novel copper-sensing two-component system for inducing Dsb gene expression in bacteria. In nature, bacteria must sense copper and tightly regulate gene expression to evade copper toxicity. Here, we identify a new copper-responsive two-component system named DsbRS in the important human pathogen Pseudomonas aeruginosa; in this system, DsbS is a sensor histidine kinase, and DsbR, its cognate response regulator, directly induces the transcription of genes involved in protein disulfide bond formation (Dsb) (i.e., the dsbDEG operon and dsbB). In the absence of copper, DsbS acts as a phosphatase toward DsbR, thus blocking the transcription of Dsb genes. In the presence of copper, the metal ion directly binds to the sensor domain of DsbS, and the Cys82 residue plays a critical role in this process. The copper-binding behavior appears to inhibit the phosphatase activity of DsbS, leading to the activation of DsbR. The copper resistance of the dsbRS knock-out mutant is restored by the ectopic expression of the dsbDEG operon, which is a DsbRS major target. Strikingly, cognates of the dsbRS-dsbDEG pair are widely distributed across eubacteria. In addition, a DsbR-binding site, which contains the consensus sequence 5'-TTA-N(8)-TTAA-3', is detected in the promoter region of dsbDEG homologs in these species. These findings suggest that the regulation of Dsb genes by DsbRS represents a novel mechanism by which bacterial cells cope with copper stress.202236546013
9088110.9038Cocrystallizing and Codelivering Complementary Drugs to Multidrugresistant Tuberculosis Bacteria in Perfecting Multidrug Therapy. Bacteria cells exhibit multidrug resistance in one of two ways: by raising the genetic expression of multidrug efflux pumps or by accumulating several drug-resistant components in many genes. Multidrug-resistive tuberculosis bacteria are treated by multidrug therapy, where a few certain antibacterial drugs are administered together to kill a bacterium jointly. A major drawback of conventional multidrug therapy is that the administration never ensures the reaching of different drug molecules to a particular bacterium cell at the same time, which promotes growing drug resistivity step-wise. As a result, it enhances the treatment time. With additional tabletability and plasticity, the formation of a cocrystal of multidrug can ensure administrating the multidrug chemically together to a target bacterium cell. With properly maintaining the basic philosophy of multidrug therapy here, the synergistic effects of drug molecules can ensure killing the bacteria, even before getting the option to raise the drug resistance against them. This can minimize the treatment span, expenditure and drug resistance. A potential threat of epidemic from tuberculosis has appeared after the Covid-19 outbreak. An unwanted loop of finding molecules with the potential to kill tuberculosis, getting their corresponding drug approvals, and abandoning the drug after facing drug resistance can be suppressed here. This perspective aims to develop the universal drug regimen by postulating the principles of drug molecule selection, cocrystallization, and subsequent harmonisation within a short period to address multidrug-resistant bacteria.202337150990
8806120.9037Cyclopropanation and membrane unsaturation improve antibiotic resistance of swarmer Pseudomonas and its sod mutants exposed to radiations, in vitro and in silico approch. It was known that UVc irradiation increases the reactive oxygen species' (ROS) levels in bacteria hence the intervention of antioxidant enzymes and causes also changes in fatty acids (FAs) composition enabling bacteria to face antibiotics. Here, we intended to elucidate an interrelationship between SOD and susceptibility to antibiotics by studying FA membrane composition of UVc-treated P. aeruginosa PAO1 and its isogenic mutants (sodM, sodB and sod MB) membrane, after treatment with antibiotics. Swarmer mutants defective in genes encoding superoxide dismutase were pre-exposed to UVc radiations and then tested by disk diffusion method for their contribution to antibiotic tolerance in comparison with the P. aeruginosa wild type (WT). Moreover, fatty acid composition of untreated and UVc-treated WT and sod mutants was examined by Gaz chromatography and correlated to antibiotic resistance. Firstly, it has been demonstrated that after UVc exposure, swarmer WT strain, sodM and sodB mutants remain resistant to polymixin B, a membrane target antibiotic, through membrane unsaturation supported by the intervention of Mn-SOD after short UVc exposure and cyclopropanation of unsaturated FAs supported by the action of Fe-SOD after longer UVc exposure. However, resistance for ciprofloxacin is correlated with increase in saturated FAs. This correlation has been confirmed by a molecular docking approach showing that biotin carboxylase, involved in the initial stage of FA biosynthesis, exhibits a high affinity for ciprofloxacin. This investigation has explored the correlation of antibiotic resistance with FA content of swarmer P.aeruginosa pre-exposed to UVc radiations, confirmed to be antibiotic target dependant.202438869625
9177130.9036Multitarget Approaches against Multiresistant Superbugs. Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.202032156116
6367140.9035Comparative Drug Resistance Reversal Potential of Natural Glycosides: Potential of Synergy Niaziridin & Niazirin. BACKGROUND: Due to the limited availability of antibiotics, Gram-negative bacteria (GNB) acquire different levels of drug resistance. It raised an urgent need to identify such agents, which can reverse the phenomenon of drug resistance. OBJECTIVE: To understand the mechanism of drug resistance reversal of glycosides; niaziridin and niazirin isolated from the pods of Moringa oleifera and ouabain (control) against the clinical isolates of multidrug-resistant Escherichia coli. METHODS: The MICs were determined following the CLSI guidelines for broth micro-dilution. In-vitro combination studies were performed by broth checkerboard method followed by Time-Kill studies, the efflux pump inhibition assay, ATPase inhibitory activity, mutation prevention concentration and in-silico studies. RESULTS: The results showed that both glycosides did not possess antibacterial activity of their own, but in combination, they reduced the MIC of tetracycline up to 16 folds. Both were found to inhibit efflux pumps, but niaziridin was the best. In real time expression pattern analysis, niaziridin was also found responsible for the down expression of the two important efflux pump acrB & yojI genes alone as well as in combination. Niaziridin was also able to over express the porin forming genes (ompA & ompX). These glycosides decreased the mutation prevention concentration of tetracycline. CONCLUSION: This is the first ever report on glycosides, niazirin and niaziridin acting as drug resistance reversal agent through efflux pump inhibition and modulation of expression pattern drug resistant genes. This study may be helpful in preparing an effective antibacterial combination against the drug-resistant GNB from a widely growing Moringa oleifera.201930977451
9734150.9034Combination of genetically diverse Pseudomonas phages enhances the cocktail efficiency against bacteria. Phage treatment has been used as an alternative to antibiotics since the early 1900s. However, bacteria may acquire phage resistance quickly, limiting the use of phage treatment. The combination of genetically diverse phages displaying distinct replication machinery in phage cocktails has therefore become a novel strategy to improve therapeutic outcomes. Here, we isolated and studied lytic phages (SPA01 and SPA05) that infect a wide range of clinical Pseudomonas aeruginosa isolates. These relatively small myophages have around 93 kbp genomes with no undesirable genes, have a 30-min latent period, and reproduce a relatively high number of progenies, ranging from 218 to 240 PFU per infected cell. Even though both phages lyse their hosts within 4 h, phage-resistant bacteria emerge during the treatment. Considering SPA01-resistant bacteria cross-resist phage SPA05 and vice versa, combining SPA01 and SPA05 for a cocktail would be ineffective. According to the decreased adsorption rate of the phages in the resistant isolates, one of the anti-phage mechanisms may occur through modification of phage receptors on the target cells. All resistant isolates, however, are susceptible to nucleus-forming jumbophages (PhiKZ and PhiPA3), which are genetically distinct from phages SPA01 and SPA05, suggesting that the jumbophages recognize a different receptor during phage entry. The combination of these phages with the jumbophage PhiKZ outperforms other tested combinations in terms of bactericidal activity and effectively suppresses the emergence of phage resistance. This finding reveals the effectiveness of the diverse phage-composed cocktail for reducing bacterial growth and prolonging the evolution of phage resistance.202337264114
6008160.9033Photopolymerized keratin-PGLa hydrogels for antibiotic resistance reversal and enhancement of infectious wound healing. Infectious wounds have become serious challenges for both treatment and management in clinical practice, so development of new antibiotics has been considered an increasingly difficult task. Here, we report the design and synthesis of keratin 31 (K31)-peptide glycine-leucine-amide (PGLa) photopolymerized hydrogels to rescue the antibiotic activity of antibiotics for infectious wound healing promotion. K31-PGLa displayed an outstanding synergistic effect with commercial antibiotics against drug-resistant bacteria by down-regulating the synthesis genes of efflux pump. Furthermore, the photopolymerized K31-PGLa/PEGDA hydrogels effectively suppressed drug-resistant bacteria growth and enhanced skin wound closure in murine. This study provided a promising alternative strategy for infectious wound treatment.202337810750
8153170.9031Dominant, Heritable Resistance to Stewart's Wilt in Maize Is Associated with an Enhanced Vascular Defense Response to Infection with Pantoea stewartii. Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart's bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.201931657672
749180.9031Omptin Proteases of Enterobacterales Show Conserved Regulation by the PhoPQ Two-Component System but Exhibit Divergent Protection from Antimicrobial Host Peptides and Complement. Bacteria that colonize eukaryotic surfaces interact with numerous antimicrobial host-produced molecules, including host defense peptides, complement, and antibodies. Bacteria have evolved numerous strategies to both detect and resist these molecules, and in the Enterobacterales order of bacteria these include alterations of the cell surface lipopolysaccharide structure and/or charge and the production of proteases that can degrade these antimicrobial molecules. Here, we show that omptin family proteases from Escherichia coli and Citrobacter rodentium are regulated by the PhoPQ system. Omptin protease activity is induced by growth in low Mg(2+), and deletion of PhoP dramatically reduces omptin protease activity, transcriptional regulation, and protein levels. We identify conserved PhoP-binding sites in the promoters of the E. coli omptin genes ompT, ompP, and arlC as well as in croP of Citrobacter rodentium and show that mutation of the putative PhoP-binding site in the ompT promoter abrogates PhoP-dependent expression. Finally, we show that although regulation by PhoPQ is conserved, each of the omptin proteins has differential activity toward host defense peptides, complement components, and resistance to human serum, suggesting that each omptin confers unique survival advantages against specific host antimicrobial factors.202336533918
674190.9031Interplay between Two-Component Regulatory Systems Is Involved in Control of Cupriavidus metallidurans Metal Resistance Genes. Metal resistance of Cupriavidus metallidurans is based on determinants that were acquired in the past by horizontal gene transfer during evolution. Some of these determinants encode transmembrane metal efflux systems. Expression of most of the respective genes is controlled by two-component regulatory systems composed of a membrane-bound sensor/sensory histidine kinase (HK) and a cytoplasmic, DNA-binding response regulator (RR). Here, we investigated the interplay between the three closely related two-component regulatory systems CzcRS, CzcR(2)S(2), and AgrRS. All three systems regulate the response regulator CzcR, while the RRs AgrR and CzcR(2) were not involved in czc regulation. Target promoters were czcNp and czcPp for genes upstream and downstream of the central czc gene region. The two systems together repressed CzcRS-dependent upregulation of czcP-lacZ at low zinc concentrations in the presence of CzcS but activated this signal transmission at higher zinc concentrations. AgrRS and CzcR(2)S(2) interacted to quench CzcRS-mediated expression of czcNp-lacZ and czcPp-lacZ. Together, cross talk between the three two-component regulatory systems enhanced the capabilities of the Czc systems by controlling expression of the additional genes czcN and czcP. IMPORTANCE Bacteria are able to acquire genes encoding resistance to metals and antibiotics by horizontal gene transfer. To bestow an evolutionary advantage on their host cell, new genes must be expressed, and their expression should be regulated so that resistance-mediating proteins are produced only when needed. Newly acquired regulators may interfere with those already present in a host cell. Such an event was studied here in the metal-resistant bacterium Cupriavidus metallidurans. The results demonstrate how regulation by the acquired genes interacts with the host's extant regulatory network. This leads to emergence of a new system level of complexity that optimizes the response of the cell to periplasmic signals.202336892288