scholarly journals Structural characterisation of a polyphosphate kinase

2014 ◽  
Vol 70 (a1) ◽  
pp. C466-C466
Author(s):  
Alice Loasby ◽  
Peter Roach ◽  
Petra Oyston
Keyword(s):  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Exothermic Reaction ◽  
Stringent Response ◽  
Titration Calorimetry ◽  
Polyphosphate Kinase ◽  
Inorganic Polyphosphate ◽  
Structural Characterisation ◽  
Signalling Molecules ◽  
Expression Of Genes

When deprived of nutrients bacteria undergo what is referred to as the `stringent response'. During the stringent response, the cell induces the expression of genes to cope with stress and starvation and diverts resources away from cell growth and division. This involves altering the cellular levels of the signalling molecules: ppGpp, pppGpp and inorganic polyphosphate (polyP)[1]. This is controlled by four enzymes; Polyphosphate kinase (Ppk), Exopolyphosphatase (Ppx), RelA and SpoT. Therefore, modulation of these enzymes is an attractive method for targeting pathogenic bacteria such as Francisella tularensis (F. tularensis), the causative agent of tularemia. FtPpk transfers phosphate from polyP to ADP to generate ATP, a reaction that is fully reversible. The importance of FtPpk in infection has been demonstrated in knockout mutants which resulted in defective growth of F. tularensis in macrophages[2]. Mutagenesis in other pathogenic bacteria has yielded attenuated mutants, suggesting an important role for Ppk in a broad spectrum of bacterial species[3]. To maximise our understanding of FtPpk, our aim was to obtain co-crystals of the enzyme and substrates. Isothermal Titration Calorimetry (ITC) was used to measure the binding of polyP and ADP to FtPpk as independent substrates. FtPpk binds ADP very weakly or not at all in the absence of polyP. FtPpk binds polyP in an exothermic reaction with a relatively high affinity (0.385 µM) in the absence of ADP. Co-crystals of FtPpk with polyP and ADP have been obtained and optimised to diffract to 2.0 Å, identifying a potential binding site for polyP. A non-hydrolysable analogue of ATP has been chemically synthesised to allow co-crystallisation experiments.

scholarly journals Targeting the Mycobacterium tuberculosis Stringent Response as a Strategy for Shortening Tuberculosis Treatment

2021 ◽  
Vol 12 ◽  
Author(s):  
Carina Danchik ◽  
Siqing Wang ◽  
Petros C. Karakousis
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Bacterial Species ◽  
Stringent Response ◽  
Therapeutic Benefit ◽  
Current Understanding ◽  
Antibiotic Tolerance ◽  
Bacterial Survival ◽  
Inorganic Polyphosphate ◽  
Regulatory Molecule ◽  
Response To Stress

The stringent response is well conserved across bacterial species and is a key pathway involved both in bacterial survival and virulence and in the induction of antibiotic tolerance in Mycobacteria. It is mediated by the alarmone (p)ppGpp and the regulatory molecule inorganic polyphosphate in response to stress conditions such as nutrient starvation. Efforts to pharmacologically target various components of the stringent response have shown promise in modulating mycobacterial virulence and antibiotic tolerance. In this review, we summarize the current understanding of the stringent response and its role in virulence and tolerance in Mycobacteria, including evidence that targeting this pathway could have therapeutic benefit.

scholarly journals Polyphosphate Kinase 2 (PPK2) Enzymes: Structure, Function, and Roles in Bacterial Physiology and Virulence

2022 ◽  
Vol 23 (2) ◽  
pp. 670
Author(s):  
Nolan Neville ◽  
Nathan Roberge ◽  
Zongchao Jia
Keyword(s):  
Molecular Chaperone ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Bacterial Virulence ◽  
Polyphosphate Kinase ◽  
Biological Functions ◽  
Inorganic Polyphosphate ◽  
Bacterial Physiology ◽  
Enzyme Families ◽  
Phosphorus Storage

Inorganic polyphosphate (polyP) has been implicated in an astonishing array of biological functions, ranging from phosphorus storage to molecular chaperone activity to bacterial virulence. In bacteria, polyP is synthesized by polyphosphate kinase (PPK) enzymes, which are broadly subdivided into two families: PPK1 and PPK2. While both enzyme families are capable of catalyzing polyP synthesis, PPK1s preferentially synthesize polyP from nucleoside triphosphates, and PPK2s preferentially consume polyP to phosphorylate nucleoside mono- or diphosphates. Importantly, many pathogenic bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii encode at least one of each PPK1 and PPK2, suggesting these enzymes may be attractive targets for antibacterial drugs. Although the majority of bacterial polyP studies to date have focused on PPK1s, PPK2 enzymes have also begun to emerge as important regulators of bacterial physiology and downstream virulence. In this review, we specifically examine the contributions of PPK2s to bacterial polyP homeostasis. Beginning with a survey of the structures and functions of biochemically characterized PPK2s, we summarize the roles of PPK2s in the bacterial cell, with a particular emphasis on virulence phenotypes. Furthermore, we outline recent progress on developing drugs that inhibit PPK2 enzymes and discuss this strategy as a novel means of combatting bacterial infections.

scholarly journals DksA Modulates Antimicrobial Susceptibility of Acinetobacter baumannii

Antibiotics ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1472
Author(s):  
Nayeong Kim ◽  
Joo-Hee Son ◽  
Kyeongmin Kim ◽  
Hyo-Jeong Kim ◽  
Minsang Shin ◽  
...  
Keyword(s):  
Gene Expression ◽  
Acinetobacter Baumannii ◽  
Antimicrobial Susceptibility ◽  
Pathogenic Bacteria ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Stringent Response ◽  
Efflux Pumps ◽  
Expression Of Genes ◽  
Mutant Strains

The stringent response regulators, (p)ppGpp and DksA, modulate various genes involved in physiological processes, virulence, and antimicrobial resistance in pathogenic bacteria. This study investigated the role of DksA in the antimicrobial susceptibility of Acinetobacter baumannii. The ∆dksA mutant (KM0248D) of A. baumannii ATCC 17978 and its complemented strain (KM0248C) were used, in addition to the ∆dksA mutant strain (NY0298D) of clinical 1656-2 strain. The microdilution assay was used to determine the minimum inhibitory concentrations (MICs) of antimicrobial agents. Quantitative real-time PCR was performed to analyze the expression of genes associated with efflux pumps. The KM0248D strain exhibited an increase of MICs to quinolones and tetracyclines, whereas KM0248D and NY0298D strains exhibited a decrease of MICs to aminoglycosides. The expression of genes associated with efflux pumps, including adeB, adeI/J, abeM, and/or tetA, was upregulated in both ∆dksA mutant strains. The deletion of dksA altered bacterial morphology in the clinical 1656-2 strain. In conclusion, DksA modulates the antimicrobial susceptibility of A. baumannii. The ∆dksA mutant strains of A. baumannii upregulate efflux pump gene expression, whereas (p)ppGpp-deficient mutants downregulate efflux pump gene expression. (p)ppGpp and DksA conduct opposite roles in the antimicrobial susceptibility of A. baumannii via efflux pump gene regulation.

scholarly journals Inorganic polyphosphate accumulation suppresses the dormancy response and virulence in Mycobacterium tuberculosis

2019 ◽  
Vol 294 (28) ◽  
pp. 10819-10832 ◽  
Author(s):  
Prabhakar Tiwari ◽  
Tannu Priya Gosain ◽  
Mamta Singh ◽  
Gaurav D. Sankhe ◽  
Garima Arora ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Transcriptional Profiling ◽  
Critical Role ◽  
Stringent Response ◽  
Growth Conditions ◽  
Therapeutic Interventions ◽  
Polyphosphate Kinase ◽  
Low Oxygen ◽  
Inorganic Polyphosphate ◽  
Double Knockout

Stringent response pathways involving inorganic polyphosphate (PolyP) play an essential role in bacterial stress adaptation and virulence. The intracellular levels of PolyP are modulated by the activities of polyphosphate kinase-1 (PPK1), polyphosphate kinase-2 (PPK2), and exopolyphosphatases (PPXs). The genome of Mycobacterium tuberculosis encodes two functional PPXs, and simultaneous deletion of ppx1 and ppx2 results in a defect in biofilm formation. We demonstrate here that these PPXs cumulatively contribute to the ability of M. tuberculosis to survive in nutrient-limiting, low-oxygen growth conditions and also in macrophages. Characterization of single (Δppx2) and double knockout (dkppx) strains of M. tuberculosis indicated that PPX-mediated PolyP degradation is essential for establishing bacterial infection in guinea pigs. RNA-Seq–based transcriptional profiling revealed that relative to the parental strain, the expression levels of DosR regulon–regulated dormancy genes were significantly reduced in the dkppx mutant strain. In concordance, we also provide evidence that PolyP inhibits the autophosphorylation activities associated with DosT and DosS sensor kinases. The results in this study uncover that enzymes involved in PolyP homeostasis play a critical role in M. tuberculosis physiology and virulence and are attractive targets for developing more effective therapeutic interventions.

Antimicrobial properties of actively purified secondary metabolites isolated from different marine organisms

2020 ◽  
Vol 21 ◽  
Author(s):  
Nilushi Indika Bamunu Arachchige ◽  
Fazlurrahman Khan ◽  
Young-Mog Kim
Keyword(s):  
Secondary Metabolites ◽  
Pathogenic Bacteria ◽  
Antimicrobial Agents ◽  
Bacterial Species ◽  
Antimicrobial Properties ◽  
Antimicrobial Effect ◽  
Cost Effective ◽  
Resistance Mechanisms ◽  
Marine Organisms ◽  
Antimicrobial Compounds

Background: The treatment of infection caused by pathogenic bacteria becomes one of the serious concerns globally. The failure in the treatment was found due to the exhibition of multiple resistance mechanisms against the antimicrobial agents. Emergence of resistant bacterial species has also been observed due to prolong treatment using conventional antibiotics. To combat these problems, several alternative strategies have been employed using biological and chemically synthesized compounds as antibacterial agents. Marine organisms considered as one of the potential sources for the isolation of bioactive compounds due to the easily available, cost-effective, and eco-friendly. Methods: The online search methodology was adapted for the collection of information related to the antimicrobial properties of marine-derived compounds. These compound has been isolated and purified by different purification techniques, and their structure also characterized. Furthermore, the antibacterial activities have been reported by using broth microdilution as well as disc diffusion assays. Results: The present review paper describes the antimicrobial effect of diverse secondary metabolites which are isolated and purified from the different marine organisms. The structural elucidation of each secondary metabolite has also been done in the present paper, which will help for the in silico designing of the novel and potent antimicrobial compounds. Conclusion: A thorough literature search has been made and summarizes the list of antimicrobial compounds that are isolated from both prokaryotic and eukaryotic marine organisms. The information obtained from the present paper will be helpful for the application of marine compounds as antimicrobial agents against different antibiotic-resistant human pathogenic bacteria.

scholarly journals Exploring Mucin as Adjunct to Phage Therapy

2021 ◽  
Vol 9 (3) ◽  
pp. 509
Author(s):  
Amanda Carroll-Portillo ◽  
Henry C. Lin
Keyword(s):  
Pathogenic Bacteria ◽  
Structural Changes ◽  
Phage Therapy ◽  
Bacterial Species ◽  
Gi Tract ◽  
Beneficial Bacteria ◽  
Phage Cocktail ◽  
Small Intestinal ◽  
Gastrointestinal Dysbiosis

Conventional phage therapy using bacteriophages (phages) for specific targeting of pathogenic bacteria is not always useful as a therapeutic for gastrointestinal (GI) dysfunction. Complex dysbiotic GI disorders such as small intestinal bowel overgrowth (SIBO), ulcerative colitis (UC), or Crohn’s disease (CD) are even more difficult to treat as these conditions have shifts in multiple populations of bacteria within the microbiome. Such community-level structural changes in the gut microbiota may require an alternative to conventional phage therapy such as fecal virome transfer or a phage cocktail capable of targeting multiple bacterial species. Additionally, manipulation of the GI microenvironment may enhance beneficial bacteria–phage interactions during treatment. Mucin, produced along the entire length of the GI tract to protect the underlying mucosa, is a prominent contributor to the GI microenvironment and may facilitate bacteria–phage interactions in multiple ways, potentially serving as an adjunct during phage therapy. In this review, we will describe what is known about the role of mucin within the GI tract and how its facilitation of bacteria–phage interactions should be considered in any effort directed at optimizing effectiveness of a phage therapy for gastrointestinal dysbiosis.

scholarly journals hfqPlays Important Roles in Virulence and Stress Adaptation in Cronobacter sakazakii ATCC 29544

2015 ◽  
Vol 83 (5) ◽  
pp. 2089-2098 ◽  
Author(s):  
Seongok Kim ◽  
Hyelyeon Hwang ◽  
Kwang-Pyo Kim ◽  
Hyunjin Yoon ◽  
Dong-Hyun Kang ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Soft Agar ◽  
Host Cells ◽  
Neonatal Meningitis ◽  
Animal Cells ◽  
Content Type ◽  
Flagellar Biosynthesis

Cronobacterspp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated withCronobacterinfection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq inC. sakazakiivirulence. In the absence ofhfq,C. sakazakiiwas highly attenuated in disseminationin vivo, showed defects in invasion (3-fold) into animal cells and survival (103-fold) within host cells, and exhibited low resistance to hydrogen peroxide (102-fold). Remarkably, the loss ofhfqled to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lackinghfq. Together, these data strongly suggest thathfqplays important roles in the virulence ofC. sakazakiiby participating in the regulation of multiple genes.

scholarly journals Detection of Food Spoilage and Pathogenic Bacteria Based on Ligation Detection Reaction Coupled to Flow-Through Hybridization on Membranes

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
K. Böhme ◽  
P. Cremonesi ◽  
M. Severgnini ◽  
Tomás G. Villa ◽  
I. C. Fernández-No ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Cost Effective ◽  
Rrna Gene ◽  
Bacterial Identification ◽  
Dot Blot ◽  
Culture Collections ◽  
Ligation Detection Reaction ◽  
Flow Through ◽  
Food Safety And Quality

Traditional culturing methods are still commonly applied for bacterial identification in the food control sector, despite being time and labor intensive. Microarray technologies represent an interesting alternative. However, they require higher costs and technical expertise, making them still inappropriate for microbial routine analysis. The present study describes the development of an efficient method for bacterial identification based on flow-through reverse dot-blot (FT-RDB) hybridization on membranes, coupled to the high specific ligation detection reaction (LDR). First, the methodology was optimized by testing different types of ligase enzymes, labeling, and membranes. Furthermore, specific oligonucleotide probes were designed based on the 16S rRNA gene, using the bioinformatic tool Oligonucleotide Retrieving for Molecular Applications (ORMA). Four probes were selected and synthesized, being specific forAeromonasspp.,Pseudomonasspp.,Shewanellaspp., andMorganella morganii, respectively. For the validation of the probes, 16 reference strains from type culture collections were tested by LDR and FT-RDB hybridization using universal arrays spotted onto membranes. In conclusion, the described methodology could be applied for the rapid, accurate, and cost-effective identification of bacterial species, exhibiting special relevance in food safety and quality.

scholarly journals Environmental modification via a quorum sensing molecule influences the social landscape of siderophore production

2017 ◽  
Vol 284 (1852) ◽  
pp. 20170200 ◽  
Author(s):  
Roman Popat ◽  
Freya Harrison ◽  
Ana C. da Silva ◽  
Scott A. S. Easton ◽  
Luke McNally ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Public Goods ◽  
Bacterial Species ◽  
Relative Fitness ◽  
Iron Starvation ◽  
Signal Molecule ◽  
Signalling Molecules ◽  
Signalling Molecule ◽  
The Impact ◽  
Social Trait

Bacteria produce a wide variety of exoproducts that favourably modify their environment and increase their fitness. These are often termed ‘public goods’ because they are costly for individuals to produce and can be exploited by non-producers (cheats). The outcome of conflict over public goods is dependent upon the prevailing environment and the phenotype of the individuals in competition. Many bacterial species use quorum sensing (QS) signalling molecules to regulate the production of public goods. QS, therefore, determines the cooperative phenotype of individuals, and influences conflict over public goods. In addition to their regulatory functions, many QS molecules have additional properties that directly modify the prevailing environment. This leads to the possibility that QS molecules could influence conflict over public goods indirectly through non-signalling effects, and the impact of this on social competition has not previously been explored. The Pseudomonas aeruginosa QS signal molecule PQS is a powerful chelator of iron which can cause an iron starvation response. Here, we show that PQS stimulates a concentration-dependent increase in the cooperative production of iron scavenging siderophores, resulting in an increase in the relative fitness of non-producing siderophore cheats. This is likely due to an increased cost of siderophore output by producing cells and a concurrent increase in the shared benefits, which accrue to both producers and cheats. Although PQS can be a beneficial signalling molecule for P. aeruginosa , our data suggest that it can also render a siderophore-producing population vulnerable to competition from cheating strains. More generally, our results indicate that the production of one social trait can indirectly affect the costs and benefits of another social trait.

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