The MisR Response Regulator Is Necessary for Intrinsic Cationic Antimicrobial Peptide and Aminoglycoside Resistance in Neisseria gonorrhoeae

Regulatory role of the Cpx ESR in bacterial behaviours

The envelope demarcates the boundary between bacterial cell and its environment, providing a place for bacteria to transport nutrients and excrete metabolic waste, while buffering external environmental stress. Envelope stress responses (ESRs) are important tools for bacteria to sense and repair envelope damage. In this review, we discussed evidence that indicates the important role of the Cpx ESR in pathogen-host interactions, including environmental stress sensing and responses, modulation of bacterial virulence, antimicrobial resistance, and inter-kingdom signaling.

Hormonal steroids induce multidrug resistance and stress response genes in Neisseria gonorrhoeae by binding to MtrR

Transcriptional regulator MtrR inhibits the expression of the multidrug efflux pump operon mtrCDE in the pathogenic bacterium Neisseria gonorrhoeae. Here, we show that MtrR binds the hormonal steroids progesterone, β-estradiol, and testosterone, which are present at urogenital infection sites, as well as ethinyl estrogen, a component of some hormonal contraceptives. Steroid binding leads to the decreased affinity of MtrR for cognate DNA, increased mtrCDE expression, and enhanced antimicrobial resistance. Furthermore, we solve crystal structures of MtrR bound to each steroid, thus revealing their binding mechanisms and the conformational changes that induce MtrR.

Transcriptional activation of ompA in Neisseria gonorrhoeae mediated by the XRE family member protein NceR

Increasing antibiotic resistance of Neisseria gonorrhoeae, the causative agent of gonorrhea, is a growing global concern that has renewed vaccine development efforts. The gonococcal OmpA protein was previously identified as a vaccine candidate due to its surface exposure, conservation, stable expression, and involvement in host-cell interactions. We previously demonstrated that the transcription of ompA can be activated by the MisR/MisS two-component system. Interestingly, earlier work suggested that the availability of free iron also influences ompA expression, which we confirmed in this study. In the present study, we found that iron regulation of ompA was independent of MisR and searched for additional regulators. A DNA pull-down assay with the ompA promoter from gonococcal lysates obtained from bacteria grown in the presence or absence of iron identified an XRE (Xenobiotic Response Element) family member protein encoded by NGO1982. We found that an NGO1982 null mutant of N. gonorrhoeae strain FA19 displayed a reduced level of ompA expression compared to the wild-type (WT) parent strain. Given this regulation, and the capacity of this XRE-like protein to regulate a gene involved in peptidoglycan biosynthesis (ltgA), along with its presence in other Neisseria sp., we termed the NGO1982-encoded protein as NceR (Neisseria cell envelope regulator). Critically, results from DNA-binding studies indicated that NceR regulates ompA through a direct mechanism. Thus, ompA expression is subject to both iron-dependent (NceR) and -independent (MisR/MisS) pathways. Hence, levels of the vaccine antigen candidate OmpA in circulating gonococcal strains could be influenced by transcriptional regulatory systems and the availability of iron. IMPORTANCE Herein, we report that the gene encoding a conserved gonococcal surface-exposed vaccine candidate (OmpA) is activated by a heretofore undescribed XRE family transcription factor, which we term NceR. We report that NceR regulation of ompA expression in N. gonorrhoeae is mediated by an iron-dependent mechanism, while the previously described MisR regulatory system is iron-independent. Our study highlights the importance of defining the complexity of coordinated genetic and physiologic systems that regulate genes encoding vaccine candidates to better understand their availability during infection.

Bacterial resistance to antibacterial agents: Mechanisms, control strategies, and implications for global health

The spread of bacterial drug resistance has posed a severe threat to public health globally. Here, we cover bacterial resistance to current antibacterial drugs, including traditional herbal medicines, conventional antibiotics, and antimicrobial peptides. We summarize the influence of bacterial drug resistance on global health and its economic burden while highlighting the resistance mechanisms developed by bacteria. Based on the One Health concept, we propose 4A strategies to combat bacterial resistance, including prudent Application of antibacterial agents, Administration, Assays, and Alternatives to antibiotics. Finally, we identify several opportunities and unsolved questions warranting future exploration for combating bacterial resistance, such as predicting genetic bacterial resistance through the use of more effective techniques, surveying both genetic determinants of bacterial resistance and the transmission dynamics of antibiotic resistance genes (ARGs).

Acclimation to Nutritional Immunity and Metal Intoxication Requires Zinc, Manganese, and Copper Homeostasis in the Pathogenic Neisseriae

Neisseria gonorrhoeae and Neisseria meningitidis are human-specific pathogens in the Neisseriaceae family that can cause devastating diseases. Although both species inhabit mucosal surfaces, they cause dramatically different diseases. Despite this, they have evolved similar mechanisms to survive and thrive in a metal-restricted host. The human host restricts, or overloads, the bacterial metal nutrient supply within host cell niches to limit pathogenesis and disease progression. Thus, the pathogenic Neisseria require appropriate metal homeostasis mechanisms to acclimate to such a hostile and ever-changing host environment. This review discusses the mechanisms by which the host allocates and alters zinc, manganese, and copper levels and the ability of the pathogenic Neisseria to sense and respond to such alterations. This review will also discuss integrated metal homeostasis in N. gonorrhoeae and the significance of investigating metal interplay.

External Stresses Affect Gonococcal Type 4 Pilus Dynamics

Bacterial type 4 pili (T4P) are extracellular polymers that serve both as adhesins and molecular motors. Functionally, they are involved in adhesion, colony formation, twitching motility, and horizontal gene transfer. T4P of the human pathogen Neisseria gonorrhoeae have been shown to enhance survivability under treatment with antibiotics or hydrogen peroxide. However, little is known about the effect of external stresses on T4P production and motor properties. Here, we address this question by directly visualizing gonococcal T4P dynamics. We show that in the absence of stress gonococci produce T4P at a remarkably high rate of ∼200 T4P min–1. T4P retraction succeeds elongation without detectable time delay. Treatment with azithromycin or ceftriaxone reduces the T4P production rate. RNA sequencing results suggest that reduced piliation is caused by combined downregulation of the complexes required for T4P extrusion from the cell envelope and cellular energy depletion. Various other stresses including inhibitors of cell wall synthesis and DNA replication, as well as hydrogen peroxide and lactic acid, inhibit T4P production. Moreover, hydrogen peroxide and acidic pH strongly affect pilus length and motor function. In summary, we show that gonococcal T4P are highly dynamic and diverse external stresses reduce piliation despite the protective effect of T4P against some of these stresses.

Neisseria gonorrhoeae physiology and pathogenesis

Neisseria gonorrhoeae is an obligate human pathogen that is the cause of the sexually transmitted disease gonorrhoea. Recently, there has been a surge in gonorrhoea cases that has been exacerbated by the rapid rise in gonococcal multidrug resistance to all useful antimicrobials resulting in this organism becoming a significant public health burden. Therefore, there is a clear and present need to understand the organism's biology through its physiology and pathogenesis to help develop new intervention strategies. The gonococcus initially colonises and adheres to host mucosal surfaces utilising a type IV pilus that helps with microcolony formation. Other adhesion strategies include the porin, PorB, and the phase variable outer membrane protein Opa. The gonococcus is able to subvert complement mediated killing and opsonisation by sialylation of its lipooligosaccharide and deploys a series of anti-phagocytic mechanisms. N. gonorrhoeae is a fastidious organism that is able to grow on a limited number of primary carbon sources such as glucose and lactate. The utilization of lactate by the gonococcus has been implicated in a number of pathogenicity mechanisms. The bacterium lives mainly in microaerobic environments and can grow both aerobically and anaerobically with the aid of nitrite. The gonococcus does not produce siderophores for scavenging iron but can utilize some produced by other bacteria, and it is able to successful chelate iron from host haem, transferrin and lactoferrin. The gonococcus is an incredibly versatile human pathogen; in the following chapter, we detail the intricate mechanisms used by the bacterium to invade and survive within the host.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Sodium Tetraphenylborate Displays Selective Bactericidal Activity against Neisseria meningitidis and N. gonorrhoeae and Is Effective at Reducing Bacterial Infection Load

Neisseria meningitidis and Neisseria gonorrhoeae, two highly related species that might have emerged from a common commensal ancestor, constitute major human threats. Vaccines are available to prevent N. meningitidis infection, whereas there are only a limited number of antibiotics available for N. gonorrhoeae Unfortunately, some strains of these species are rapidly evolving and capable of escaping human interventions. Thus, it is now urgent to develop new avenues to fight these bacteria. This study reports that a boron-based salt, sodium tetraphenylborate (NaBPh₄), displays high bactericidal activity and remarkable specificity against N. meningitidis and N. gonorrhoeae Other closely related commensal species such as Neisseria lactamica, which is found in the normal flora of healthy individuals, were found to be less affected even at 5-fold higher doses of NaBPh₄ This specificity was further observed when much lower sensitivity was found for more distant Neisseriaceae species (such as Neisseria elongata or Kingella oralis) and completely unrelated species. Significant boron uptake by N. meningitidis cells was observed after incubation with 5 μM NaBPh₄, as measured by inductively coupled plasma mass spectrometry, suggesting that this drug candidate's target(s) could be located intracellularly or within the cell envelope. Furthermore, mutants with slightly decreased susceptibility displayed alterations in genes coding for cell envelope elements, which reduced their virulence in an animal model of infection. Finally, a single dose of NaBPh₄ resulted in a significant reduction in bacterial burden in a mouse model of N. meningitidis bacteremia. Although numerous boron-containing species were previously reported for their complex biological activities, the observation of this narrow selectivity is unprecedented and of potential importance from a therapeutic standpoint.

A small molecule that mitigates bacterial infection disrupts Gram-negative cell membranes and is inhibited by cholesterol and neutral lipids

Infections caused by Gram-negative bacteria are difficult to fight because these pathogens exclude or expel many clinical antibiotics and host defense molecules. However, mammals have evolved a substantial immune arsenal that weakens pathogen defenses, suggesting the feasibility of developing therapies that work in concert with innate immunity to kill Gram-negative bacteria. Using chemical genetics, we recently identified a small molecule, JD1, that kills Salmonella enterica serovar Typhimurium (S. Typhimurium) residing within macrophages. JD1 is not antibacterial in standard microbiological media, but rapidly inhibits growth and curtails bacterial survival under broth conditions that compromise the outer membrane or reduce efflux pump activity. Using a combination of cellular indicators and super resolution microscopy, we found that JD1 damaged bacterial cytoplasmic membranes by increasing fluidity, disrupting barrier function, and causing the formation of membrane distortions. We quantified macrophage cell membrane integrity and mitochondrial membrane potential and found that disruption of eukaryotic cell membranes required approximately 30-fold more JD1 than was needed to kill bacteria in macrophages. Moreover, JD1 preferentially damaged liposomes with compositions similar to E. coli inner membranes versus mammalian cell membranes. Cholesterol, a component of mammalian cell membranes, was protective in the presence of neutral lipids. In mice, intraperitoneal administration of JD1 reduced tissue colonization by S. Typhimurium. These observations indicate that during infection, JD1 gains access to and disrupts the cytoplasmic membrane of Gram-negative bacteria, and that neutral lipids and cholesterol protect mammalian membranes from JD1-mediated damage. Thus, it may be possible to develop therapeutics that exploit host innate immunity to gain access to Gram-negative bacteria and then preferentially damage the bacterial cell membrane over host membranes.

Transcriptional control of the gonococcal ompA gene by the MisR/MisS two-component regulatory system

Neisseria gonorrhoeae, the causative agent of gonorrhea, is an exclusive human pathogen whose growing antibiotic resistance is causing worldwide concern. The increasing rise of antibiotic resistance expressed by gonococci highlights the need to find alternative approaches to current gonorrhea treatment such as vaccine development or novel therapeutics. The gonococcal OmpA protein was previously identified as a potential vaccine candidate due to its conservation and stable expression amongst strains of Neisseria gonorrhoeae. However, factors that might modulate levels of OmpA and therefore potential vaccine efficacy are unknown. Earlier work indicated that ompA is part of the MisR/MisS regulon and suggested that it was a MisR-activated gene. Herein, we confirmed MisR/MisS regulation of ompA and report that the MisR response regulator can bind upstream of the ompA translational start codon. Further, we describe the contribution of a DNA sequence upstream of the ompA promoter that is critical for MisR activation of ompA transcription. Our results provide a framework for understanding the transcription of gonococcal ompA through a regulatory system known to be important for survival of gonococci during experimental infection.

Intimate Relations: Molecular and Immunologic Interactions Between Neisseria gonorrhoeae and HIV-1

While the global incidence of human immunodeficiency virus (HIV-1) remains well above UNAIDS targets, sexual transmission HIV is surprisingly inefficient. A variety of host, viral and environmental factors can either increase HIV-1 shedding in the infected partner and/or increase mucosal susceptibility of the HIV-1 uninfected partner. Clinical and epidemiological studies have clearly established that Neisseria gonorrhoeae substantially enhances HIV-1 transmission, despite it not being an ulcerative infection. This review will consider findings from molecular, immunologic and clinical studies that have focused on each of these two human-restricted pathogens, in order to develop an integrative model that describes how gonococci can both increase mucosal shedding of HIV-1 from a co-infected person and facilitate virus establishment in a susceptible host.

Coevolution of Resistance Against Antimicrobial Peptides

Antimicrobial peptides (AMPs) are produced by all forms of life, ranging from eukaryotes to prokaryotes, and they are a crucial component of innate immunity, involved in clearing infection by inhibiting pathogen colonization. In the recent past, AMPs received high attention due to the increase of extensive antibiotic resistance by these pathogens. AMPs exhibit a diverse spectrum of activity against bacteria, fungi, parasites, and various types of cancer. AMPs are active against various bacterial pathogens that cause disease in animals and plants. However, because of the coevolution of host and pathogen interaction, bacteria have developed the mechanisms to sense and exhibit an adaptive response against AMPs. These resistance mechanisms are playing an important role in bacterial virulence within the host. Here, we have discussed the different resistance mechanisms used by gram-positive and gram-negative bacteria to sense and combat AMP actions. Understanding the mechanism of AMP resistance may provide directions toward the development of novel therapeutic strategies to control multidrug-resistant pathogens.

Antimicrobial Peptides: Virulence and Resistance Modulation in Gram-Negative Bacteria

Growing resistance to antibiotics is one of the biggest threats to human health. One of the possibilities to overcome this resistance is to use and develop alternative molecules such as antimicrobial peptides (AMPs). However, an increasing number of studies have shown that bacterial resistance to AMPs does exist. Since AMPs are immunity molecules, it is important to ensure that their potential therapeutic use is not harmful in the long term. Recently, several studies have focused on the adaptation of Gram-negative bacteria to subinhibitory concentrations of AMPs. Such concentrations are commonly found in vivo and in the environment. It is therefore necessary to understand how bacteria detect and respond to low concentrations of AMPs. This review focuses on recent findings regarding the impact of subinhibitory concentrations of AMPs on the modulation of virulence and resistance in Gram-negative bacteria.

Global Network Analysis of Neisseria gonorrhoeae Identifies Coordination between Pathways, Processes, and Regulators Expressed during Human Infection

Neisseria gonorrhoeae is a Gram-negative diplococcus that is responsible for the sexually transmitted infection gonorrhea, a high-morbidity disease in the United States and worldwide. Over the past several years, N. gonorrhoeae strains resistant to antibiotics used to treat this infection have begun to emerge across the globe. Thus, new treatment strategies are needed to combat this organism. Here, we utilized N. gonorrhoeae transcriptomic data sets, including those obtained from natural infection of the human genital tract, to infer the first global gene coexpression network of this pathogen. Interrogation of this network revealed genes central to the network that are likely critical for gonococcal growth, metabolism, and virulence, including genes encoding hypothetical proteins expressed during mucosal infection. In addition, network analysis revealed overlap in the response of N. gonorrhoeae to incubation with neutrophils and exposure to hydrogen peroxide stress in vitro Network analysis also identified new targets of the gonococcal global regulatory protein Fur, while examination of the network neighborhood of genes allowed us to assign additional putative categories to several proteins. Collectively, the characterization of the first gene coexpression network for N. gonorrhoeae described here has revealed new regulatory pathways and new categories for proteins and has shown how processes important to gonococcal infection in both men and women are linked. This information fills a critical gap in our understanding of virulence strategies of this obligate human pathogen and will aid in the development of new treatment strategies for gonorrhea.IMPORTANCE Neisseria gonorrhoeae is the causative agent of the sexually transmitted infection (STI) gonorrhea, a disease with high morbidity worldwide with an estimated 87 million cases annually. Current therapeutic and pharmacologic approaches to treat gonorrhea have been compromised by increased antibiotic resistance worldwide, including to the most recent FDA-approved antibiotic. New treatment strategies are urgently needed to combat this organism. In this study, we used network analysis to interrogate and define the coordination of pathways and processes in N. gonorrhoeae An analysis of the gonococcal network was also used to assign categories to genes and to expand our understanding of regulatory strategies. Network analysis provides important insights into pathogenic mechanisms of this organism that will guide the design of new strategies for disease treatment.

Maintaining Integrity Under Stress: Envelope Stress Response Regulation of Pathogenesis in Gram-Negative Bacteria

The Gram-negative bacterial envelope is an essential interface between the intracellular and harsh extracellular environment. Envelope stress responses (ESRs) are crucial to the maintenance of this barrier and function to detect and respond to perturbations in the envelope, caused by environmental stresses. Pathogenic bacteria are exposed to an array of challenging and stressful conditions during their lifecycle and, in particular, during infection of a host. As such, maintenance of envelope homeostasis is essential to their ability to successfully cause infection. This review will discuss our current understanding of the σ^E- and Cpx-regulated ESRs, with a specific focus on their role in the virulence of a number of model pathogens.

Roles of two-component regulatory systems in antibiotic resistance

Two-component regulatory systems (TCSs) are a major mechanism by which bacteria sense and respond to changes in their environment. TCSs typically consist of two proteins that bring about major regulation of the cell genome through coordinated action mediated by phosphorylation. Environmental conditions that activate TCSs are numerous and diverse and include exposure to antibiotics as well as conditions inside a host. The resulting regulatory action often involves activation of antibiotic defenses and changes to cell physiology that increase antibiotic resistance. Examples of resistance mechanisms enacted by TCSs contained in this review span those found in both Gram-negative and Gram-positive species and include cell surface modifications, changes in cell permeability, increased biofilm formation, and upregulation of antibiotic-degrading enzymes.

Gonococcal Defenses against Antimicrobial Activities of Neutrophils

Neisseria gonorrhoeae initiates a strong local immune response that is characterized by copious recruitment of neutrophils to the site of infection. Neutrophils neutralize microbes by mechanisms that include phagocytosis, extracellular trap formation, production of reactive oxygen species, and the delivery of antimicrobial granular contents. However, neutrophils do not clear infection with N. gonorrhoeae. N. gonorrhoeae not only expresses factors that defend against neutrophil bactericidal components, but it also manipulates neutrophil production and release of these components. In this review, we highlight the numerous approaches used by N. gonorrhoeae to survive exposure to neutrophils both intracellularly and extracellularly. These approaches reflect the exquisite adaptation of N. gonorrhoeae to its obligate human host.

Pathogenesis of Neisseria gonorrhoeae in the female reproductive tract: neutrophilic host response, sustained infection, and clinical sequelae

PURPOSE OF REVIEW

Gonorrhea is a major global health concern, caused by the bacterium Neisseria gonorrhoeae. The main clinical feature of acute gonorrhea is neutrophilic influx that is unable to clear infection. Women of reproductive age are predominantly at risk for serious sequelae of gonorrhea, including pelvic inflammatory disease, ectopic pregnancy, and infertility. This review will highlight how neutrophils are recruited to the female reproductive tract (FRT) in response to N. gonorrhoeae, how N. gonorrhoeae resists killing by neutrophils, and the connection between neutrophilic inflammation and cellular damage.

RECENT FINDINGS

Epithelial cells and immune cells of the FRT recognize and respond to N. gonorrhoeae lipid A and heptose bisphosphate of lipooligosaccharide, porin, lipoproteins, and peptidoglycan fragments. N. gonorrhoeae skews the resulting immune response toward a neutrophilic, Th17-like response. N. gonorrhoeae has multiple, nonredundant mechanisms to survive inside neutrophils and in neutrophil extracellular traps. Infection that ascends to the upper FRT induces the further release of inflammatory cytokines and matrix metalloproteinases, which cause epithelial damage.

SUMMARY

N. gonorrhoeae is remarkable in its ability to recruit neutrophils, yet survive in their midst. New models being developed for FRT infection with N. gonorrhoeae will be useful to reveal the mechanisms underlying these observations.

Transcriptome Analysis of Neisseria gonorrhoeae during Natural Infection Reveals Differential Expression of Antibiotic Resistance Determinants between Men and Women

Recent emergence of antimicrobial resistance of Neisseria gonorrhoeae worldwide has resulted in limited therapeutic choices for treatment of infections caused by this organism. We performed global transcriptomic analysis of N. gonorrhoeae in subjects with gonorrhea who attended a Nanjing, China, sexually transmitted infection (STI) clinic, where antimicrobial resistance of N. gonorrhoeae is high and increasing. We found that N. gonorrhoeae transcriptional responses to infection differed in genital specimens taken from men and women, particularly antibiotic resistance gene expression, which was increased in men. These sex-specific findings may provide a new approach to guide therapeutic interventions and preventive measures that are also sex specific while providing additional insight to address antimicrobial resistance of N. gonorrhoeae.

Neisseria gonorrhoeae is a bacterial pathogen responsible for the sexually transmitted infection gonorrhea. Emergence of antimicrobial resistance (AMR) of N. gonorrhoeae worldwide has resulted in limited therapeutic choices for this infection. Men who seek treatment often have symptomatic urethritis; in contrast, gonococcal cervicitis in women is usually minimally symptomatic, but may progress to pelvic inflammatory disease. Previously, we reported the first analysis of gonococcal transcriptome expression determined in secretions from women with cervical infection. Here, we defined gonococcal global transcriptional responses in urethral specimens from men with symptomatic urethritis and compared these with transcriptional responses in specimens obtained from women with cervical infections and in vitro-grown N. gonorrhoeae isolates. This is the first comprehensive comparison of gonococcal gene expression in infected men and women. RNA sequencing analysis revealed that 9.4% of gonococcal genes showed increased expression exclusively in men and included genes involved in host immune cell interactions, while 4.3% showed increased expression exclusively in women and included phage-associated genes. Infected men and women displayed comparable antibiotic-resistant genotypes and in vitro phenotypes, but a 4-fold higher expression of the Mtr efflux pump-related genes was observed in men. These results suggest that expression of AMR genes is programed genotypically and also driven by sex-specific environments. Collectively, our results indicate that distinct N. gonorrhoeae gene expression signatures are detected during genital infection in men and women. We propose that therapeutic strategies could target sex-specific differences in expression of antibiotic resistance genes.

IMPORTANCE Recent emergence of antimicrobial resistance of Neisseria gonorrhoeae worldwide has resulted in limited therapeutic choices for treatment of infections caused by this organism. We performed global transcriptomic analysis of N. gonorrhoeae in subjects with gonorrhea who attended a Nanjing, China, sexually transmitted infection (STI) clinic, where antimicrobial resistance of N. gonorrhoeae is high and increasing. We found that N. gonorrhoeae transcriptional responses to infection differed in genital specimens taken from men and women, particularly antibiotic resistance gene expression, which was increased in men. These sex-specific findings may provide a new approach to guide therapeutic interventions and preventive measures that are also sex specific while providing additional insight to address antimicrobial resistance of N. gonorrhoeae.

Both MisR (CpxR) and MisS (CpxA) Are Required for Neisseria gonorrhoeae Infection in a Murine Model of Lower Genital Tract Infection

During infection, Neisseria gonorrhoeae senses and responds to stress; such responses may be modulated by MisRS (NGO0177 and NGO0176), a two-component system that is a homolog of CpxRA. In Escherichia coli, CpxRA senses and responds to envelope stress; CpxA is a sensor kinase/phosphatase for CpxR, a response regulator. When a cpxA mutant is grown in medium containing glucose, CpxR is phosphorylated by acetyl phosphate but cannot be dephosphorylated, resulting in constitutive activation. Kandler and coworkers (J. L. Kandler, C. L. Holley, J. L. Reimche, V. Dhulipala, J. T. Balthazar, A. Muszyński, R. W. Carlson, and W. M. Shafer, Antimicrob Agents Chemother 60:4690-4700, 2016, https://doi.org/10.1128/AAC.00823-16) showed that MisR (CpxR) is required for the maintenance of membrane integrity and resistance to antimicrobial peptides, suggesting a role in gonococcal survival in vivo Here, we evaluated the contributions of MisR and MisS (CpxA) to gonococcal infection in a murine model of cervicovaginal colonization and identified MisR-regulated genes using RNA sequencing (RNA-Seq). The deletion of misR or misS severely reduced the capacity of N. gonorrhoeae to colonize mice or maintain infection over a 7-day period and reduced microbial fitness after exposure to heat shock. Compared to the wild type (WT), the inactivation of misR identified 157 differentially regulated genes, most of which encoded putative envelope proteins. The inactivation of misS identified 17 differentially regulated genes compared to the WT and 139 differentially regulated genes compared to the misR mutant, 111 of which overlapped those differentially expressed in the comparison of the WT versus the misR mutant. These data indicate that an intact MisRS system is required for gonococcal infection of mice. Provided the MisR is constitutively phosphorylated in the misS mutant, the data suggest that controlled but not constitutive activation is required for gonococcal infection in mice.