Regulation of antibiotic persistence and pathogenesis in Acinetobacter baumannii by glutamate and histidine metabolic pathways. - Related Documents




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14301.0000Regulation of antibiotic persistence and pathogenesis in Acinetobacter baumannii by glutamate and histidine metabolic pathways. BACKGROUND: Metabolite production is essential for the proliferation and environmental adaptation of all living organisms. In pathogenic bacteria, metabolite exchange during host infection can regulate their physiology and virulence. However, there is still much unknown about which specific metabolic pathways in pathogenic bacteria respond to changes in the environment during infections. This study examines how pathogenic bacterium Acinetobacter baumannii uses particular metabolic pathways to regulate its ability to antibiotic persistence and pathogenesis. RESULTS: To determine specific metabolic pathways in pathogenic antibiotic resistance bacteria, metabolite profiles of bacteria were constructed using ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry and multivariate statistical analysis. A. baumannii generates amino acid derivative metabolites, which are precursors for fatty acid production. Comparative genomic analysis identified specific genes regulating the production of these metabolites and fatty acids in A. baumannii. Inactivation of genes involved in glutamate metabolism, gdhA, aspB, murI1, and racD, impairs antibiotic persistence, while inactivation of the hisC gene, encoding histidinol - phosphate aminotransferase enzyme in histidine metabolic pathway, increases bacterial survival inside macrophages during infections. CONCLUSIONS: This study reports that A. baumannii regulates antibiotic persistence and pathogenesis through glutamate and histidine metabolic pathways, respectively. These findings suggest that specific metabolic pathways regulate bacterial pathogenesis and antibiotic persistence during infections, providing potential therapeutic targets for pathogenic bacteria.202539953398
892210.9997Transitioning from Soil to Host: Comparative Transcriptome Analysis Reveals the Burkholderia pseudomallei Response to Different Niches. Burkholderia pseudomallei, a soil and water saprophyte, is responsible for the tropical human disease melioidosis. A hundred years since its discovery, there is still much to learn about B. pseudomallei proteins that are essential for the bacterium's survival in and interaction with the infected host, as well as their roles within the bacterium's natural soil habitat. To address this gap, bacteria grown under conditions mimicking the soil environment were subjected to transcriptome sequencing (RNA-seq) analysis. A dual RNA-seq approach was used on total RNA from spleens isolated from a B. pseudomallei mouse infection model at 5 days postinfection. Under these conditions, a total of 1,434 bacterial genes were induced, with 959 induced in the soil environment and 475 induced in bacteria residing within the host. Genes encoding metabolism and transporter proteins were induced when the bacteria were present in soil, while virulence factors, metabolism, and bacterial defense mechanisms were upregulated during active infection of mice. On the other hand, capsular polysaccharide and quorum-sensing pathways were inhibited during infection. In addition to virulence factors, reactive oxygen species, heat shock proteins, siderophores, and secondary metabolites were also induced to assist bacterial adaptation and survival in the host. Overall, this study provides crucial insights into the transcriptome-level adaptations which facilitate infection by soil-dwelling B. pseudomallei. Targeting novel therapeutics toward B. pseudomallei proteins required for adaptation provides an alternative treatment strategy given its intrinsic antimicrobial resistance and the absence of a vaccine. IMPORTANCE Burkholderia pseudomallei, a soil-dwelling bacterium, is the causative agent of melioidosis, a fatal infectious disease of humans and animals. The bacterium has a large genome consisting of two chromosomes carrying genes that encode proteins with important roles for survival in diverse environments as well as in the infected host. While a general mechanism of pathogenesis has been proposed, it is not clear which proteins have major roles when the bacteria are in the soil and whether the same proteins are key to successful infection and spread. To address this question, we grew the bacteria in soil medium and then in infected mice. At 5 days postinfection, bacteria were recovered from infected mouse organs and their gene expression was compared against that of bacteria grown in soil medium. The analysis revealed a list of genes expressed under soil growth conditions and a different set of genes encoding proteins which may be important for survival, replication, and dissemination in an infected host. These proteins are a potential resource for understanding the full adaptation mechanism of this pathogen. In the absence of a vaccine for melioidosis and with treatment being reliant on combinatorial antibiotic therapy, these proteins may be ideal targets for designing antimicrobials to treat melioidosis.202336856434
887220.9996Dictyostelium discoideum as a model system for identification of Burkholderia pseudomallei virulence factors. Burkholderia pseudomallei is an emerging bacterial pathogen and category B biothreat. Human infections with B. pseudomallei (called melioidosis) present as a range of manifestations, including acute septicemia and pneumonia. Although melioidosis can be fatal, little is known about the molecular basis of B. pseudomallei pathogenicity, in part because of the lack of simple, genetically tractable eukaryotic models to facilitate en masse identification of virulence determinants or explore host-pathogen interactions. Two assays, one high-throughput and one quantitative, were developed to monitor levels of resistance of B. pseudomallei and the closely related nearly avirulent species Burkholderia thailandensis to predation by the phagocytic amoeba Dictyostelium discoideum. The quantitative assay showed that levels of resistance to, and survival within, amoeba by these bacteria and their known virulence mutants correlate well with their published levels of virulence in animals. Using the high-throughput assay, we screened a 1,500-member B. thailandensis transposon mutant library and identified 13 genes involved in resistance to predation by D. discoideum. Orthologs of these genes were disrupted in B. pseudomallei, and nearly all mutants had similarly decreased resistance to predation by D. discoideum. For some mutants, decreased resistance also correlated with reduced survival in and cytotoxicity toward macrophages, as well as attenuated virulence in mice. These observations suggest that some factors required by B. pseudomallei for resistance to environmental phagocytes also aid in resistance to phagocytic immune cells and contribute to disease in animals. Thus, D. discoideum provides a novel, high-throughput model system for facilitating inquiry into B. pseudomallei virulence.201121402765
831130.9996Perturbation of Quorum Sensing after the Acquisition of Bacteriophage Resistance Could Contribute to Novel Traits in Vibrio alginolyticus. Bacteria employ a wide range of molecular mechanisms to confer resistance to bacteriophages, and these mechanisms are continuously being discovered and characterized. However, there are instances where certain bacterial species, despite lacking these known mechanisms, can still develop bacteriophage resistance through intricate metabolic adaptation strategies, potentially involving mutations in transcriptional regulators or phage receptors. Vibrio species have been particularly useful for studying the orchestrated metabolic responses of Gram-negative marine bacteria in various challenges. In a previous study, we demonstrated that Vibrio alginolyticus downregulates the expression of specific receptors and transporters in its membrane, which may enable the bacterium to evade infection by lytic bacteriophages. In our current study, our objective was to explore how the development of bacteriophage resistance in Vibrio species disrupts the quorum-sensing cascade, subsequently affecting bacterial physiology and metabolic capacity. Using a real-time quantitative PCR (rt-QPCR) platform, we examined the expression pattern of quorum-sensing genes, auto-inducer biosynthesis genes, and cell density regulatory proteins in phage-resistant strains. Our results revealed that bacteriophage-resistant bacteria downregulate the expression of quorum-sensing regulatory proteins, such as LuxM, LuxN, and LuxP. This downregulation attenuates the normal perception of quorum-sensing peptides and subsequently diminishes the expression of cell density regulatory proteins, including LuxU, aphA, and LuxR. These findings align with the diverse phenotypic traits observed in the phage-resistant strains, such as altered biofilm formation, reduced planktonic growth, and reduced virulence. Moreover, the transcriptional depletion of aphA, the master regulator associated with low cell density, was linked to the downregulation of genes related to virulence. This phenomenon appears to be phage-specific, suggesting a finely tuned metabolic adaptation driven by phage-host interaction. These findings contribute to our understanding of the role of Vibrio species in microbial marine ecology and highlight the complex interplay between phage resistance, quorum sensing, and bacterial physiology.202337764117
933840.9996Polyamines in bacteria: pleiotropic effects yet specific mechanisms. Extensive data in a wide range of organisms point to the importance of polyamine homeostasis for growth. The two most common polyamines found in bacteria are putrescine and spermidine. The investigation of polyamine function in bacteria has revealed that they are involved in a number of functions other than growth, which include incorporation into the cell wall and biosynthesis of siderophores. They are also important in acid resistance and can act as a free radical ion scavenger. More recently it has been suggested that polyamines play a potential role in signaling cellular differentiation in Proteus mirabilis. Polyamines have also been shown to be essential in biofilm formation in Yersinia pestis. The pleiotropic nature of polyamines has made their investigation difficult, particularly in discerning any specific effect from more global growth effects. Here we describe key developments in the investigation of the function of polyamines in bacteria that have revealed new roles for polyamines distinct from growth. We describe the bacterial genes necessary for biosynthesis and transport, with a focus on Y. pestis. Finally we review a novel role for polyamines in the regulation of biofilm development in Y. pestis and provide evidence that the investigation of polyamines in Y. pestis may provide a model for understanding the mechanism through which polyamines regulate biofilm formation.200717966408
830550.9996Light Modulates Metabolic Pathways and Other Novel Physiological Traits in the Human Pathogen Acinetobacter baumannii. Light sensing in chemotrophic bacteria has been relatively recently ascertained. In the human pathogen Acinetobacter baumannii, light modulates motility, biofilm formation, and virulence through the blue-light-sensing-using flavin (BLUF) photoreceptor BlsA. In addition, light can induce a reduction in susceptibility to certain antibiotics, such as minocycline and tigecycline, in a photoreceptor-independent manner. In this work, we identified new traits whose expression levels are modulated by light in this pathogen, which comprise not only important determinants related to pathogenicity and antibiotic resistance but also metabolic pathways, which represents a novel concept for chemotrophic bacteria. Indeed, the phenylacetic acid catabolic pathway and trehalose biosynthesis were modulated by light, responses that completely depend on BlsA. We further show that tolerance to some antibiotics and modulation of antioxidant enzyme levels are also influenced by light, likely contributing to bacterial persistence in adverse environments. Also, we present evidence indicating that surfactant production is modulated by light. Finally, the expression of whole pathways and gene clusters, such as genes involved in lipid metabolism and genes encoding components of the type VI secretion system, as well as efflux pumps related to antibiotic resistance, was differentially induced by light. Overall, our results indicate that light modulates global features of the A. baumannii lifestyle.IMPORTANCE The discovery that nonphototrophic bacteria respond to light constituted a novel concept in microbiology. In this context, we demonstrated that light could modulate aspects related to bacterial virulence, persistence, and resistance to antibiotics in the human pathogen Acinetobacter baumannii In this work, we present the novel finding that light directly regulates metabolism in this chemotrophic bacterium. Insights into the mechanism show the involvement of the photoreceptor BlsA. In addition, tolerance to antibiotics and catalase levels are also influenced by light, likely contributing to bacterial persistence in adverse environments, as is the expression of the type VI secretion system and efflux pumps. Overall, a profound influence of light on the lifestyle of A. baumannii is suggested to occur.201728289081
68660.9996SigB-dependent general stress response in Bacillus subtilis and related gram-positive bacteria. One of the strongest and most noticeable responses of Bacillus subtilis cells to a range of stress and starvation stimuli is the dramatic induction of about 150 SigB-dependent general stress genes. The activity of SigB itself is tightly regulated by a complex signal transduction cascade with at least three main signaling pathways that respond to environmental stress, energy depletion, or low temperature. The SigB-dependent response is conserved in related gram-positive bacteria but is missing in strictly anaerobic or in some facultatively anaerobic gram-positive bacteria. It covers functions from nonspecific and multiple stress resistance to the control of virulence in pathogenic bacteria. A comprehensive understanding of this crucial stress response is essential not only for bacterial physiology but also for applied microbiology, including pathogenicity and pathogen control.200718035607
832470.9996Bile Sensing: The Activation of Vibrio parahaemolyticus Virulence. Bacteria must develop resistance to various inhospitable conditions in order to survive in the human gastrointestinal tract. Bile, which is secreted by the liver, and plays an important role in food digestion also has antimicrobial properties and is able to disrupt cellular homeostasis. Paradoxically, although bile is one of the guts defenses, many studies have reported that bacteria such as Vibrio parahaemolyticus can sense bile and use its presence as an environmental cue to upregulate virulence genes during infection. This article aims to discuss how bile is detected by V. parahaemolyticus and its role in regulating type III secretion system 2 leading to human infection. This bile-bacteria interaction pathway gives us a clearer understanding of the biochemical and structural analysis of the bacterial receptors involved in mediating a response to bile salts which appear to be a significant environmental cue during initiation of an infection.201728484445
832380.9996The impact of environmental stress on Listeria monocytogenes virulence. Listeria monocytogenes, a significant food-borne pathogen, must defy a variety of conditions encountered in the food environment and during the infection process. In reaction to adverse conditions, the bacteria significantly change their metabolism, inducing a stress response which is mediated by a range of alternative sigma factors. The extent of the response to stress was shown to vary in the L. monocytogenes population. According to recent evidence a major L. monocytogenes alternative sigma factor, designated sigma B (sigma B), regulates some virulence genes in response to stress, which supports an older hypothesis that stress-resistant strains should be more pathogenic. The induction of sigma B-dependent genes may also be important from the point of view of food hygiene. It seems that stress response activation can paradoxically enhance resistance to agents used in food preservation. Therefore, monitoring the expression of sigma B-dependent genes can serve as a useful marker to assess the innate resistance of L. monocytogenes strains. This knowledge will allow the design of new methods with sequential preservation steps that could inactivate the bacteria without inducing their stress response.200920169937
830290.9996Auxin-mediated regulation of susceptibility to toxic metabolites, c-di-GMP levels, and phage infection in the rhizobacterium Serratia plymuthica. The communication between plants and their microbiota is highly dynamic and involves a complex network of signal molecules. Among them, the auxin indole-3-acetic acid (IAA) is a critical phytohormone that not only regulates plant growth and development, but is emerging as an important inter- and intra-kingdom signal that modulates many bacterial processes that are important during interaction with their plant hosts. However, the corresponding signaling cascades remain largely unknown. Here, we advance our understanding of the largely unknown mechanisms by which IAA carries out its regulatory functions in plant-associated bacteria. We showed that IAA caused important changes in the global transcriptome of the rhizobacterium Serratia plymuthica and multidisciplinary approaches revealed that IAA sensing interferes with the signaling mediated by other pivotal plant-derived signals such as amino acids and 4-hydroxybenzoic acid. Exposure to IAA caused large alterations in the transcript levels of genes involved in amino acid metabolism, resulting in significant metabolic alterations. IAA treatment also increased resistance to toxic aromatic compounds through the induction of the AaeXAB pump, which also confers resistance to IAA. Furthermore, IAA promoted motility and severely inhibited biofilm formation; phenotypes that were associated with decreased c-di-GMP levels and capsule production. IAA increased capsule gene expression and enhanced bacterial sensitivity to a capsule-dependent phage. Additionally, IAA induced the expression of several genes involved in antibiotic resistance and led to changes in the susceptibility and responses to antibiotics with different mechanisms of action. Collectively, our study illustrates the complexity of IAA-mediated signaling in plant-associated bacteria. IMPORTANCE: Signal sensing plays an important role in bacterial adaptation to ecological niches and hosts. This communication appears to be particularly important in plant-associated bacteria since they possess a large number of signal transduction systems that respond to a wide diversity of chemical, physical, and biological stimuli. IAA is emerging as a key inter- and intra-kingdom signal molecule that regulates a variety of bacterial processes. However, despite the extensive knowledge of the IAA-mediated regulatory mechanisms in plants, IAA signaling in bacteria remains largely unknown. Here, we provide insight into the diversity of mechanisms by which IAA regulates primary and secondary metabolism, biofilm formation, motility, antibiotic susceptibility, and phage sensitivity in a biocontrol rhizobacterium. This work has important implications for our understanding of bacterial ecology in plant environments and for the biotechnological and clinical applications of IAA, as well as related molecules.202438837409
698100.9996Genome-wide transcriptional changes induced by phagocytosis or growth on bacteria in Dictyostelium. BACKGROUND: Phagocytosis plays a major role in the defense of higher organisms against microbial infection and provides also the basis for antigen processing in the immune response. Cells of the model organism Dictyostelium are professional phagocytes that exploit phagocytosis of bacteria as the preferred way to ingest food, besides killing pathogens. We have investigated Dictyostelium differential gene expression during phagocytosis of non-pathogenic bacteria, using DNA microarrays, in order to identify molecular functions and novel genes involved in phagocytosis. RESULTS: The gene expression profiles of cells incubated for a brief time with bacteria were compared with cells either incubated in axenic medium or growing on bacteria. Transcriptional changes during exponential growth in axenic medium or on bacteria were also compared. We recognized 443 and 59 genes that are differentially regulated by phagocytosis or by the different growth conditions (growth on bacteria vs. axenic medium), respectively, and 102 genes regulated by both processes. Roughly one third of the genes are up-regulated compared to macropinocytosis and axenic growth. Functional annotation of differentially regulated genes with different tools revealed that phagocytosis induces profound changes in carbohydrate, amino acid and lipid metabolism, and in cytoskeletal components. Genes regulating translation and mitochondrial biogenesis are mostly up-regulated. Genes involved in sterol biosynthesis are selectively up-regulated, suggesting a shift in membrane lipid composition linked to phagocytosis. Very few changes were detected in genes required for vesicle fission/fusion, indicating that the intracellular traffic machinery is mostly in common between phagocytosis and macropinocytosis. A few putative receptors, including GPCR family 3 proteins, scaffolding and adhesion proteins, components of signal transduction and transcription factors have been identified, which could be part of a signalling complex regulating phagocytosis and adaptational downstream responses. CONCLUSION: The results highlight differences between phagocytosis and macropinocytosis, and provide the basis for targeted functional analysis of new candidate genes and for comparison studies with transcriptomes during infection with pathogenic bacteria.200818559084
8242110.9996New antibacterial targets: Regulation of quorum sensing and secretory systems in zoonotic bacteria. Quorum sensing (QS) is a communication mechanism that controls bacterial communication and can influence the transcriptional expression of multiple genes through one or more signaling molecules, thereby coordinating the population response of multiple bacterial pathogens. Secretion systems (SS) play an equally important role in bacterial information exchange, relying on the secretory systems to secrete proteins that act as virulence factors to promote adhesion to host cells. Eight highly efficient SS have been described, all of which are involved in the secretion or transfer of virulence factors, and the effector proteins they secrete play a key role in the virulence and pathogenicity of bacteria. It has been shown that many bacterial SS are directly or indirectly regulated by QS and thus influence bacterial virulence and antibiotic resistance. This review describes the relationship between QS and SS of several common zoonotic pathogenic bacteria and outlines the molecular mechanisms of how QS systems regulate SS, to provide a theoretical basis for the study of bacterial pathogenicity and the development of novel antibacterial drugs.202337343493
8966120.9996Gene expression profile of Campylobacter jejuni in response to macrolide antibiotics. Campylobacter jejuni is a foodborne pathogen that causes gastroenteritis in humans and has developed resistance to various antibiotics. The primary objective of this research was to examine the network of antibiotic resistance in C. jejuni. The study involved the wild and antibiotic-resistant strains placed in the presence and absence of antibiotics to review their gene expression profiles in response to ciprofloxacin via microarray. Differentially expressed genes (DEGs) analysis and Protein-Protein Interaction (PPI) Network studies were performed for these genes. The results showed that the resistance network of C. jejuni is modular, with different genes involved in bacterial motility, capsule synthesis, efflux, and amino acid and sugar synthesis. Antibiotic treatment resulted in the down-regulation of cluster genes related to translation, flagellum formation, and chemotaxis. In contrast, cluster genes involved in homeostasis, capsule formation, and cation efflux were up-regulated. The study also found that macrolide antibiotics inhibit the progression of C. jejuni infection by inactivating topoisomerase enzymes and increasing the activity of epimerase enzymes, trying to compensate for the effect of DNA twisting. Then, the bacterium limits the movement to conserve energy. Identifying the antibiotic resistance network in C. jejuni can aid in developing drugs to combat these bacteria. Genes involved in cell division, capsule formation, and substance transport may be potential targets for inhibitory drugs. Future research must be directed toward comprehending the underlying mechanisms contributing to the modularity of antibiotic resistance and developing strategies to disrupt and mitigate the growing threat of antibiotic resistance effectively.202438393387
9337130.9996Predation-resistant Pseudomonas bacteria engage in symbiont-like behavior with the social amoeba Dictyostelium discoideum. The soil amoeba Dictyostelium discoideum acts as both a predator and potential host for diverse bacteria. We tested fifteen Pseudomonas strains that were isolated from transiently infected wild D. discoideum for ability to escape predation and infect D. discoideum fruiting bodies. Three predation-resistant strains frequently caused extracellular infections of fruiting bodies but were not found within spores. Furthermore, infection by one of these species induces secondary infections and suppresses predation of otherwise edible bacteria. Another strain can persist inside of amoebae after being phagocytosed but is rarely taken up. We sequenced isolate genomes and discovered that predation-resistant isolates are not monophyletic. Many Pseudomonas isolates encode secretion systems and toxins known to improve resistance to phagocytosis in other species, as well as diverse secondary metabolite biosynthetic gene clusters that may contribute to predation resistance. However, the distribution of these genes alone cannot explain why some strains are edible and others are not. Each lineage may employ a unique mechanism for resistance.202337884792
685140.9996Implication 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
8294150.9995Unraveling the genetic mechanisms of UV radiation resistance in Bacillus through biofilm formation, sporulation, and carotenoid production. Bacillus species are Gram-positive bacteria that are rod-shaped, endospore-forming, and aerobic or facultatively anaerobic. With over 300 recognized species, Bacillus subtilis stands out as a well-studied model organism. The genus's various species exhibit a wide range of physiological capabilities, allowing them to thrive in diverse environmental conditions. Each cell produces a single endospore, which is highly resistant to heat, cold, radiation, desiccation, and disinfectants. Among Bacillus strains, those capable of producing spores, biofilms, and carotenoids demonstrate significant resilience to UV light. This review examines the genes involved in spore formation, biofilm development, and carotenoid synthesis, emphasizing their roles in UV radiation survival. We explore the interconnections between these processes and their combined contribution to UV resistance, focusing on the underlying genetic mechanisms. These insights will benefit researchers studying the genetic basis of UV radiation resistance in Bacillus species. IMPORTANCE: Bacteria employ adaptive strategies in extreme environments through rapid changes in gene expression, altering their phenotype for survival. Bacillus species, for example, defend against UV radiation by making spores, creating biofilms, and producing pigments. During sporulation, sigma factors (σ(F), σ(E), σ(G), and σ(K)) regulate gene expression to adapt to environmental shifts. It has been found that the spores of some species may contain pigments that strongly absorb UV radiation, playing a crucial role in spore UV resistance. UV light penetrates biofilm matrices minimally, mainly affecting surface cells, which produce compounds like mycosporine-like amino acids and carotenoids to shield against UV damage.202540456420
8308160.9995PhoPQ Regulates Quinolone and Cephalosporin Resistance Formation in Salmonella Enteritidis at the Transcriptional Level. The two-component system (TCS) PhoPQ has been demonstrated to be crucial for the formation of resistance to quinolones and cephalosporins in Salmonella Enteritidis (S. Enteritidis). However, the mechanism underlying PhoPQ-mediated antibiotic resistance formation remains poorly understood. Here, it was shown that PhoP transcriptionally regulated an assortment of genes associated with envelope homeostasis, the osmotic stress response, and the redox balance to confer resistance to quinolones and cephalosporins in S. Enteritidis. Specifically, cells lacking the PhoP regulator, under nalidixic acid and ceftazidime stress, bore a severely compromised membrane on the aspects of integrity, fluidity, and permeability, with deficiency to withstand osmolarity stress, an increased accumulation of intracellular reactive oxygen species, and dysregulated redox homeostasis, which are unfavorable for bacterial survival. The phosphorylated PhoP elicited transcriptional alterations of resistance-associated genes, including the outer membrane porin ompF and the aconitate hydratase acnA, by directly binding to their promoters, leading to a limited influx of antibiotics and a well-maintained intracellular metabolism. Importantly, it was demonstrated that the cavity of the PhoQ sensor domain bound to and sensed quinolones/cephalosporins via the crucial surrounding residues, as their mutations abrogated the binding and PhoQ autophosphorylation. This recognition mode promoted signal transduction that activated PhoP, thereby modulating the transcription of downstream genes to accommodate cells to antibiotic stress. These findings have revealed how bacteria employ a specific TCS to sense antibiotics and combat them, suggesting PhoPQ as a potential drug target with which to surmount S. Enteritidis. IMPORTANCE The prevalence of quinolone and cephalosporin-resistant S. Enteritidis is of increasing clinical concern. Thus, it is imperative to identify novel therapeutic targets with which to treat S. Enteritidis-associated infections. The PhoPQ two-component system is conserved across a variety of Gram-negative pathogens, by which bacteria adapt to a range of environmental stimuli. Our earlier work has demonstrated the importance of PhoPQ in the resistance formation in S. Enteritidis to quinolones and cephalosporins. In the current work, we identified a global profile of genes that are regulated by PhoP under antibiotic stresses, with a focus on how PhoP regulated downstream genes, either positively or negatively. Additionally, we established that PhoQ sensed quinolones and cephalosporins in a manner of directly binding to them. These identified genes and pathways that are mediated by PhoPQ represent promising targets for the development of a drug potentiator with which to neutralize antibiotic resistance in S. Enteritidis.202337184399
6342170.9995Determinants of Extreme β-Lactam Tolerance in the Burkholderia pseudomallei Complex. Slow-growing bacteria are insensitive to killing by antibiotics, a trait known as antibiotic tolerance. In this study, we characterized the genetic basis of an unusually robust β-lactam (meropenem) tolerance seen in Burkholderia species. We identified tolerance genes under three different slow-growth conditions by extensive transposon mutant sequencing (Tn-seq), followed by single mutant validation. There were three principal findings. First, mutations in a small number of genes reduced tolerance under multiple conditions. Most of the functions appeared to be specific to peptidoglycan synthesis and the response to its disruption by meropenem action rather than being associated with more general physiological processes. The top tolerance genes are involved in immunity toward a type VI toxin targeting peptidoglycan (BTH_I0069), peptidoglycan recycling (ldcA), periplasmic regulation by proteolysis (prc), and an envelope stress response (rpoE and degS). Second, most of the tolerance functions did not contribute to growth in the presence of meropenem (intrinsic resistance), indicating that the two traits are largely distinct. Third, orthologues of many of the top Burkholderia thailandensis tolerance genes were also important in Burkholderia pseudomallei Overall, these studies show that the determinants of meropenem tolerance differ considerably depending on cultivation conditions, but that there are a few shared functions with strong mutant phenotypes that are important in multiple Burkholderia species.201829439964
9137180.9995Virulence- and antibiotic resistance-associated two-component signal transduction systems of Gram-positive pathogenic bacteria as targets for antimicrobial therapy. Two-component signal transduction systems are central elements of the virulence and antibiotic resistance responses of opportunistic bacterial pathogens. These systems allow the bacterium to sense and respond to signals emanating from the host environment and to modulate the repertoire of genes expressed to allow invasion and growth in the host. The integral role of two-component systems in virulence and antibiotic sensitivity, and the existence of essential two-component systems in several pathogenic bacteria, suggests that these systems may be novel targets for antimicrobial intervention. This review discusses the potential use of two-component systems as targets for antimicrobial therapy against Gram-positive pathogens and the current status in the development of inhibitors specific for these systems.200212191621
681190.9995Global transcriptional response to vancomycin in Mycobacterium tuberculosis. In order to gain additional understanding of the physiological mechanisms used by bacteria to maintain surface homeostasis and to identify potential targets for new antibacterial drugs, we analysed the variation of the Mycobacterium tuberculosis transcriptional profile in response to inhibitory and subinhibitory concentrations of vancomycin. Our analysis identified 153 genes differentially regulated after exposing bacteria to a concentration of the drug ten times higher than the MIC, and 141 genes differentially expressed when bacteria were growing in a concentration of the drug eightfold lower than the MIC. Hierarchical clustering analysis indicated that the response to these different conditions is different, although with some overlap. This approach allowed us to identify several genes whose products could be involved in the protection from antibiotic stress targeting the envelope and help to confer the basal level of M. tuberculosis resistance to antibacterial drugs, such as Rv2623 (UspA-like), Rv0116c, PE20-PPE31, PspA and proteins related to toxin-antitoxin systems. Moreover, we also demonstrated that the alternative sigma factor sigma(E) confers basal resistance to vancomycin, once again underlining its importance in the physiology of the mycobacterial surface stress response.200919332811