scholarly journals Colistin heteroresistance in Enterobacter cloacae is mediated by PmrAB-independent 4-amino-4-deoxy-L-arabinose addition to lipid A

2019 ◽  
Author(s):  
Katie N. Kang ◽  
Dustin R. Klein ◽  
Misha I. Kazi ◽  
François Guérin ◽  
Vincent Cattoir ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Lipid A ◽  
Enterobacter Cloacae ◽  
Two Component System ◽  
Cationic Antimicrobial Peptide ◽  
Component System ◽  
Gram Negative ◽  
Nosocomial Pathogens ◽  
Majority Population ◽  
Two Component

AbstractThe Enterobacter cloacae complex (ECC) consists of closely-related, but genetically distinct bacteria commonly associated with the human microbiota. ECC have been increasingly isolated from healthcare-associated infections, demonstrating that these Enterobacteriaceae are emerging nosocomial pathogens. ECC strains can rapidly acquire multidrug resistance to conventional antibiotics. Cationic antimicrobial peptides (CAMPs) have served as therapeutic alternatives because they target the highly conserved lipid A component of the Gram-negative outer membrane to lyse the bacterial cell. Many Gram-negative Enterobacteriaceae fortify their outer membrane with cationic amine-containing moieties to protect from CAMP-inflicted lysis. The PmrAB two-component system (TCS) transcriptionally activates 4-amino-4-deoxy-L-arabinose (L-Ara4N) biosynthesis to result in amine moiety addition to lipid A in many Enterobacteriaceae such as E. coli and Salmonella. In contrast, PmrAB in E. cloacae is dispensable for CAMP resistance. Instead, fitness against CAMPs presents as heteroresistance, or a subpopulation of cells that exhibit clinically significant increases in resistance levels compared to the majority population. We demonstrate that E. cloacae lipid A is modified with L-Ara4N to induce CAMP heteroresistance and that the regulatory mechanism is independent of the PmrABEcl TCS. We show that the response regulator, PhoPEcl, directly binds to the arnBEcl promoter to induce expression of L-Ara4N biosynthesis and PmrAB-independent addition to the lipid A disaccharolipid. Therefore, we have identified a mechanism of ECC colistin heteroresistance that directly involves the PhoPQ system.ImportanceMembers of the Enterobacter cloacae complex (ECC) are Gram-negative nosocomial pathogens that have emerged within healthcare facilities around the world. ECC infections are associated with immunocompromised patients and infections are often life threatening. The cationic antimicrobial peptide, colistin (polymyxin E), is a last-line treatment option to combat Gram-negative multidrug resistant infections. However, many ECC intrinsically encode a colistin heteroresistance mechanism. Our analysis to characterize colistin heteroresistance in E. cloacae revealed that 4-amino-4-deoxy-L-arabinose is conjugated to the lipid A disaccharolipid to protect from colistin-mediated lysis. Additionally, this mechanism is directly regulated by the PhoPQEcl two-component system. Elucidation of outer membrane antimicrobial resistance modifications and their regulatory pathways in E. cloacae isolates will advance our understanding of CAMP heteroresistance.

scholarly journals Regulatory Roles of the GacS/GacA Two-Component System in Plant-Associated and Other Gram-Negative Bacteria

2001 ◽  
Vol 14 (12) ◽  
pp. 1351-1363 ◽  
Author(s):  
Stephan Heeb ◽  
Dieter Haas
Keyword(s):  
Rna Binding ◽  
Enteric Bacteria ◽  
Plant Diseases ◽  
Gram Negative Bacteria ◽  
Two Component System ◽  
Component System ◽  
Gram Negative ◽  
Ecological Fitness ◽  
Two Component ◽  
Sensor Kinases

The sensor kinase GacS and the response regulator GacA are members of a two-component system that is present in a wide variety of Gram-negative bacteria and has been studied mainly in enteric bacteria and fluorescent pseudomonads. The GacS/GacA system controls the production of secondary metabolites and extracellular enzymes involved in pathogenicity to plants and animals, biocontrol of soilborne plant diseases, ecological fitness, or tolerance to stress. A current model proposes that GacS senses a still-unknown signal and activates, via a phosphorelay mechanism, the GacA transcription regulator, which in turn triggers the expression of target genes. The GacS protein belongs to the unorthodox sensor kinases, characterized by an autophosphorylation, a receiver, and an output domain. The periplasmic loop domain of GacS is poorly conserved in diverse bacteria. Thus, a common signal interacting with this domain would be unexpected. Based on a comparison with the transcriptional regulator NarL, a secondary structure can be predicted for the GacA sensor kinases. Certain genes whose expression is regulated by the GacS/GacA system are regulated in parallel by the small RNA binding protein RsmA (CsrA) at a posttranscriptional level. It is suggested that the GacS/GacA system operates a switch between primary and secondary metabolism, with a major involvement of posttranscriptional control mechanisms.

How the PhoP/PhoQ System Controls Virulence and Mg 2+ Homeostasis: Lessons in Signal Transduction, Pathogenesis, Physiology, and Evolution

2021 ◽  
Author(s):  
Eduardo A. Groisman ◽  
Alexandre Duprey ◽  
Jeongjoon Choi
Keyword(s):  
Antimicrobial Agents ◽  
Bacterial Species ◽  
Transcriptional Regulator ◽  
Acidic Ph ◽  
Two Component System ◽  
Component System ◽  
Gram Negative ◽  
Content Type ◽  
Two Component ◽  
Serovar Typhimurium

The PhoP/PhoQ two-component system governs virulence, Mg 2+ homeostasis, and resistance to a variety of antimicrobial agents, including acidic pH and cationic antimicrobial peptides, in several Gram-negative bacterial species. Best understood in Salmonella enterica serovar Typhimurium, the PhoP/PhoQ system consists of the sensor PhoQ and the transcriptional regulator PhoP.

scholarly journals Reinforcing Lipid A Acylation on the Cell Surface of Acinetobacter baumannii Promotes Cationic Antimicrobial Peptide Resistance and Desiccation Survival

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Joseph M. Boll ◽  
Ashley T. Tucker ◽  
Dustin R. Klein ◽  
Alexander M. Beltran ◽  
Jennifer S. Brodbelt ◽  
...  
Keyword(s):  
Health Care ◽  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Lipid A ◽  
Treatment Options ◽  
Cationic Antimicrobial Peptide ◽  
Gram Negative ◽  
Content Type ◽  
Hospital Environments ◽  
Lipid A Biosynthesis

ABSTRACTAcinetobacter baumanniiis an emerging Gram-negative pathogen found in hospitals and intensive care units. In order to persist in hospital environments,A. baumanniiwithstands desiccative conditions and can rapidly develop multidrug resistance to conventional antibiotics. Cationic antimicrobial peptides (CAMPs) have served as therapeutic alternatives because they target the conserved lipid A component of the Gram-negative outer membrane to lyse the bacterial cell. However, many Gram-negative pathogenic bacteria, includingA. baumannii, fortify their outer membrane with hepta-acylated lipid A to protect the cell from CAMP-dependent cell lysis. Whereas inEscherichia coliandSalmonella, increased production of the outer membrane acyltransferase PagP results in formation of protective hepta-acylated lipid A, which reinforces the lipopolysaccharide portion of the outer membrane barrier,A. baumanniidoes not carry a gene that encodes a PagP homolog. Instead,A. baumanniihas evolved a PagP-independent mechanism to synthesize protective hepta-acylated lipid A. Taking advantage of a recently adaptedA. baumanniigenetic recombineering system, we characterized two putative acyltransferases inA. baumanniidesignated LpxLAb(A. baumanniiLpxL) and LpxMAb(A. baumanniiLpxM), which transfer one and two lauroyl (C12:0) acyl chains, respectively, during lipid A biosynthesis. Hepta-acylation ofA. baumanniilipid A promoted resistance to vertebrate and polymyxin CAMPs, which are prescribed as last-resort treatment options. Intriguingly, our analysis also showed that LpxMAb-dependent acylation of lipid A is essential forA. baumanniidesiccation survival, a key resistance mechanism for survival in hospital environments. Compounds that inhibit LpxMAb-dependent hepta-acylation of lipid A could act synergistically with CAMPs to provide innovative transmission prevention strategies and treat multidrug-resistant infections.IMPORTANCEAcinetobacter baumanniiinfections can be life threatening, and disease can progress in a variety of host tissues. Current antibiotic regimen and disinfectant strategies have failed to limit nosocomialA. baumanniiinfections. Instead, the rate ofA. baumanniiinfection among health care communities has skyrocketed due to the bacterium's adaptability. Its aptitude for survival over extended periods on inanimate objects, such as catheters, respirators, and surfaces in intensive care units, or on the hands of health care workers and its ability to rapidly develop antibiotic resistance makeA. baumanniia threat to health care communities. Emergence of multidrug- and extremely drug-resistantA. baumanniiillustrates the ineffectiveness of current prevention and treatment options. Our analysis to understand howA. baumanniiresists cationic antimicrobial peptide (CAMP)-mediated and desiccative killing revealed two lipid A acyltransferases that produce protective hepta-acylated lipid A. Our work suggests that inhibiting lipid A biosynthesis by targeting the acyltransferase LpxMAb(A. baumanniiLpxM) could provide a novel target to combat this pathogen.

scholarly journals Various novel colistin resistance mechanisms interact to facilitate adaptation of Aeromonas hydrophila to complex colistin environments

2021 ◽  
Author(s):  
Junqi Liu ◽  
Gang Xiao ◽  
Wangping Zhou ◽  
Jun Yang ◽  
Yang Wang ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Bacterial Survival ◽  
Colistin Resistance ◽  
Two Component System ◽  
Component System ◽  
Gram Negative ◽  
Two Component ◽  
High Level

Aeromonas hydrophila, a heterotrophic and Gram-negative bacterium, has attracted considerable attention owing to the increasing prevalence of reported infections. Colistin is a last-resort antibiotic that can treat life-threatening infections caused by multidrug-resistant gram-negative bacteria. However, the mechanisms underlying colistin resistance in A. hydrophila remain unclear. The present study reveals four novel colistin resistance mechanisms in A. hydrophila: (i) EnvZ/OmpR upregulates the expression of the arnBCADTEF operon to mediate LPS modification by 4-amino-4-deoxy-L-arabinose; (ii) EnvZ/OmpR regulates the expression of the autotransporter gene3832 to decrease outer membrane permeability in response to colistin; (iii) deletion of envZ/ompR activates PhoP/PhoQ, which functions as a substitute two-component system to mediate the addition of phosphoethanolamine to lipid A via pmrC; and (iv) the mlaFD173A mutant confers high-level colistin resistance via upregulation of the Mla pathway. The EnvZ/OmpR two-component system-mediated resistance mechanism is the leading form of colistin resistance in A. hydrophila, which enables it to rapidly generate low- to medium-level colistin resistance. As colistin concentrations in the environment continue to rise, antibiotic resistance mediated by EnvZ/OmpR becomes insufficient to ensure bacterial survival. Consequently, A. hydrophila has developed a mlaF mutation that results in high-level colistin resistance. Our findings indicate that A. hydrophila can thrive in a complex environment through various colistin resistance mechanisms.

scholarly journals The Two-Component System CprRS Senses Cationic Peptides and Triggers Adaptive Resistance in Pseudomonas aeruginosa Independently of ParRS

2012 ◽  
Vol 56 (12) ◽  
pp. 6212-6222 ◽  
Author(s):  
Lucía Fernández ◽  
Håvard Jenssen ◽  
Manjeet Bains ◽  
Irith Wiegand ◽  
W. James Gooderham ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Peptides ◽  
Outer Membrane ◽  
Dependent Manner ◽  
Two Component System ◽  
Concentration Dependent Manner ◽  
Component System ◽  
Content Type ◽  
Wide Range ◽  
Two Component

ABSTRACTCationic antimicrobial peptides pass across the outer membrane by interacting with negatively charged lipopolysaccharide (LPS), leading to outer membrane permeabilization in a process termed self-promoted uptake. Resistance can be mediated by the addition of positively charged arabinosamine through the action of thearnBCADTEFoperon. We recently described a series of two-component regulators that lead to the activation of thearnoperon after recognizing environmental signals, including low-Mg2+(PhoPQ, PmrAB) or cationic (ParRS) peptides. However, some peptides did not activate thearnoperon through ParRS. Here, we report the identification of a new two-component system, CprRS, which, upon exposure to a wide range of antimicrobial peptides, triggered the expression of the LPS modification operon. Thus, mutations in thecprRSoperon blocked the induction of thearnoperon in response to several antimicrobial peptides independently of ParRS but did not affect the response to low Mg2+. Distinct patterns ofarninduction were identified. Thus, the responses to polymyxins were abrogated by eitherparRorcprRmutations, while responses to other peptides, including indolicidin, showed differential dependency on the CprRS and ParRS systems in a concentration-dependent manner. It was further demonstrated that, following exposure to inducing antimicrobial peptides,cprRSmutants did not become adaptively resistant to polymyxins as was observed for wild-type cells. Our microarray studies demonstrated that the CprRS system controlled a quite modest regulon, indicating that it was quite specific to adaptive peptide resistance. These findings provide greater insight into the complex regulation of LPS modification inPseudomonas aeruginosa, which involves the participation of at least 4 two-component systems.

scholarly journals Peptide Antibiotic Sensing and Detoxification Modules ofBacillus subtilis

2010 ◽  
Vol 55 (2) ◽  
pp. 515-525 ◽  
Author(s):  
Anna Staroń ◽  
Dora Elisabeth Finkeisen ◽  
Thorsten Mascher
Keyword(s):  
Abc Transporter ◽  
Regulatory Sequences ◽  
Peptide Antibiotic ◽  
Peptide Antibiotics ◽  
Two Component System ◽  
Cationic Antimicrobial Peptide ◽  
Component System ◽  
Lipid Ii ◽  
Wide Range ◽  
Two Component

ABSTRACTPeptide antibiotics are produced by a wide range of microorganisms. Most of them target the cell envelope, often by inhibiting cell wall synthesis. One of the resistance mechanisms against antimicrobial peptides is a detoxification module consisting of a two-component system and an ABC transporter. Upon the detection of such a compound, the two-component system induces the expression of the ABC transporter, which in turn removes the antibiotic from its site of action, mediating the resistance of the cell. Three such peptide antibiotic-sensing and detoxification modules are present inBacillus subtilis. Here we show that each of these modules responds to a number of peptides and confers resistance against them. BceRS-BceAB (BceRS-AB) responds to bacitracin, plectasin, mersacidin, and actagardine. YxdJK-LM is induced by a cationic antimicrobial peptide, LL-37. The PsdRS-AB (formerly YvcPQ-RS) system responds primarily to lipid II-binding lantibiotics such as nisin and gallidermin. We characterized thepsdRS-ABoperon and defined the regulatory sequences within the PpsdApromoter. Mutation analysis demonstrated that PpsdAexpression is fully PsdR dependent. The features of both the PbceAand PpsdApromoters make them promising candidates as novel whole-cell biosensors that can easily be adjusted for high-throughput screening.

scholarly journals The Lipoprotein NlpE Is a Cpx Sensor That Serves as a Sentinel for Protein Sorting and Folding Defects in theEscherichia coliEnvelope

2019 ◽  
Vol 201 (10) ◽  
Author(s):  
Antoine Delhaye ◽  
Géraldine Laloux ◽  
Jean-François Collet
Keyword(s):  
Outer Membrane ◽  
Two Component System ◽  
Oxidative Folding ◽  
Component System ◽  
Content Type ◽  
E Coli ◽  
Outer Membrane Lipoprotein ◽  
Physiological Relevance ◽  
Two Component ◽  
Membrane Lipoprotein

ABSTRACTThe envelope of Gram-negative bacteria is a complex compartment that is essential for viability. To ensure survival of the bacterial cells in fluctuating environments, several signal transduction systems, called envelope stress response systems (ESRSs), exist to monitor envelope biogenesis and homeostasis. The Cpx two-component system is an extensively studied ESRS inEscherichia colithat is active during exposure to a vast array of stresses and protects the envelope under those harmful circumstances. Overproduction of NlpE, a two-domain outer membrane lipoprotein of unclear function, has been used in numerous studies as a molecular trigger to turn on the system artificially. However, the mechanism of Cpx activation by NlpE, as well as its physiological relevance, awaited further investigation. In this paper, we provide novel insights into the role played by NlpE in the Cpx system. We found that, among all outer membrane lipoproteins inE. coli, NlpE is sufficient to induce Cpx when lipoprotein trafficking is perturbed. Under such conditions, fitness is increased by the presence of NlpE. Moreover, we show that NlpE, through its N-terminal domain, physically interacts with the Cpx sensor kinase CpxA. Our data suggest that NlpE also serves to activate the Cpx system during oxidative folding defects in the periplasm and that its C-terminal domain is involved in the sensing mechanism. Overall, our data demonstrate that NlpE acts as a sentinel for two important envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding, and they further establish NlpE as a bona fide member of the Cpx two-component system.IMPORTANCEBacteria rely on a sophisticated envelope to shield them against challenging environmental conditions and therefore need to ensure correct envelope assembly and integrity. A major signaling pathway that performs this role in Gram-negative species is the Cpx system. An outer membrane lipoprotein of unclear function, NlpE, has long been exploited as a research tool to study Cpx inE. coli, since it triggers this system when overproduced or mislocalized; however, the mechanism and physiological relevance of the NlpE-Cpx connection have awaited further investigation. We elucidate a new function for NlpE by showing that it physically interacts with the Cpx sensor CpxA and acts as a sentinel that specifically monitors two essential envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding.

scholarly journals The Vibrio cholerae VprA-VprB Two-Component System Controls Virulence through Endotoxin Modification

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Carmen M. Herrera ◽  
Alexander A. Crofts ◽  
Jeremy C. Henderson ◽  
S. Cassandra Pingali ◽  
Bryan W. Davies ◽  
...  
Keyword(s):  
Immune System ◽  
Antimicrobial Peptides ◽  
Vibrio Cholerae ◽  
Lipid A ◽  
Host Immune System ◽  
Two Component System ◽  
Cationic Antimicrobial Peptides ◽  
Component System ◽  
Content Type ◽  
Two Component

ABSTRACTThe bacterial cell surface is the first structure the host immune system targets to prevent infection. Cationic antimicrobial peptides of the innate immune system bind to the membrane of Gram-negative pathogens via conserved, surface-exposed lipopolysaccharide (LPS) molecules. We recently reported that modern strains of the global intestinal pathogenVibrio choleraemodify the anionic lipid A domain of LPS with a novel moiety, amino acids. Remarkably, glycine or diglycine addition to lipid A alters the surface charge of the bacteria to help evade the cationic antimicrobial peptide polymyxin. However, the regulatory mechanisms of lipid A modification inV. choleraeare unknown. Here, we identify a novel two-component system that regulates lipid A glycine modification by responding to important biological cues associated with pathogenesis, including bile, mildly acidic pH, and cationic antimicrobial peptides. The histidine kinase Vc1319 (VprB) and the response regulator Vc1320 (VprA) respond to these signals and are required for the expression of thealmEFGoperon that encodes the genes essential for glycine modification of lipid A. Importantly, both the newly identified two-component system and the lipid A modification machinery are required for colonization of the mammalian host. This study demonstrates howV. choleraeuses a previously unknown regulatory network, independent of well-studiedV. choleraevirulence factors and regulators, to respond to the host environment and cause infection.IMPORTANCEVibrio cholerae, the etiological agent of cholera disease, infects millions of people every year.V. choleraeEl Tor and classical biotypes have been responsible for all cholera pandemics. The El Tor biotype responsible for the current seventh pandemic has displaced the classical biotype worldwide and is highly resistant to cationic antimicrobial peptides, like polymyxin B. This resistance arises from the attachment of one or two glycine residues to the lipid A domain of lipopolysaccharide, a major surface component of Gram-negative bacteria. Here, we identify the VprAB two-component system that regulates the charge of the bacterial surface by directly controlling the expression of genes required for glycine addition to lipid A. The VprAB-dependent lipid A modification confers polymyxin B resistance and contributes significantly to pathogenesis. This finding is relevant for understanding howVibrio choleraehas evolved mechanisms to facilitate the evasion of the host immune system and increase bacterial fitness.

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