SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
A series of phenazine compounds, including 15 synthetics and a natural derivative, iodinin, were tested for inhibition of selected phytopathogenic bacteria and fungi. Eleven of the compounds had bacteriostatic activity for Xanthomonas oryzae. Three other species of Xanthomonas were resistant. Phenazine 5-oxide was the most effective phenazine against the bacterial leaf blight.
Pantoea agglomerans strain Eh1087 produces the phenazine antibiotic D-alanylgriseoluteic acid. A glutamine auxotroph harboring an insertion in a putative glnA gene was obtained by transposon-mutagenesis of Eh1087 that produced less D-alanylgriseoluteic acid than the parental strain (strain Eh7.1). Cosmids encoding the Eh1087 glnA were isolated by their ability to complement the mutant for prototrophy. The role of the Eh1087 glnA locus was functionally confirmed by complementation of an Escherichia coli glnA mutant. Analysis of the nucleotide and deduced amino acid sequences of the Eh1087 glnA gene indicated a high degree of similarity to the glnA genes and glutamine synthetase enzymes of other Enterobacteriaceae. Isotopic labelling experiments with 15N-labelled ammonium sulfate demonstrated that wild-type Eh1087 incorporated 15N into griseoluteic acid more readily than the glnA mutant Eh7.1. We conclude that the 2 nitrogens in the phenazine nucleus originate from glutamine and the intracellular glutamine synthesized by Eh1087 is a source of the phenazine nucleus nitrogens even in glutamine-rich environments.
The phenazines include upward of 50 pigmented, heterocyclic nitrogen-containing secondary metabolites synthesized by some strains of fluorescent Pseudomonas spp. and a few other bacterial genera. The antibiotic properties of these compounds have been known for over 150 years, but advances within the past two decades have provided significant new insights into the genetics, biochemistry, and regulation of phenazine synthesis, as well as the mode of action and functional roles of these compounds in the environment. This new knowledge reveals conservation of biosynthetic enzymes across genera but raises questions about conserved biosynthetic mechanisms, and sets the stage for improving the performance of phenazine producers used as biological control agents for soilborne plant pathogens.
BACKGROUND: A dramatic increase in multiple-drug-resistant (MDR) Gram-positive pathogens has occurred in recent times, leading to increased rates or morbidity and mortality and also associated with high costs for the treatment of these infections. It is clear that there is an urgent need for the development of effective antimicrobial agents. The anti-bacterial activity of seven 2,2,6,6-tetramethylpiperidine (TMP)-substituted phenazines, compared to clofazimine (B663), were tested against 70 clinical isolates of methicillin-resistant Staphylococcus aureus, MDR Streptococcus pneumoniae and resistant Enterococcus sp. METHODS: Standard minimum inhibitory concentration agar dilution susceptibility tests were done on all isolates, including ATCC control strains. RESULTS: All the TMP-substituted phenazines were more active than clofazimine against all isolates tested. Compound B4125 was the most active by inhibiting all growth of the organisms tested, including vancomycin-resistant Enterococcus faecium. CONCLUSION: Clofazimine has been shown to have anti-staphylococcal activity. We demonstrate enhanced anti-bacterial activity of TMP-substituted phenazines against drug-resistant Gram-positive organisms compared to clofazimine.
Four new members of the phenazine family, endophenazines A-D, and the already known phenazine-1-carboxylic acid (tubermycin B) were detected in the culture broth of various endosymbiotic Streptomyces anulatus strains by chemical screening in a combination of TLC-staining reagents and HPLC-diode array analysis. The endosymbiotic strains were isolated from four different arthropod hosts at various sites. The new phenazine compounds showed antimicrobial activities against Gram-positive bacteria and some filamentous fungi, and herbicidal activity against Lemna minor (duckweed).
A series of cobalt (III) complexes, [Co(Racac)2(L)]+, have been prepared as potential hypoxia-selective prointercalator forms of the ligands L, where L is the cytotoxic DNA mono-intercalating ligands N-[2-[(aminoethyl)amino]ethyl]-phenazine-1-carboxamide and N-[5-[(aminoethyl)amino]pentyl]-phenazine-1-carboxamide or the potentially bis(intercalating) ligand bis[2-(phenazine-1-carboxamido)ethyl]-1,2-diaminoethane. The cobalt(III) complexes of the monointercalating ligands have significantly lower DNA binding affinity and cytotoxicity than the ligands themselves, indicating the potential utility of this prodrug approach for deactivation (and release under hypoxic conditions). However, the complexes showed only low hypoxic selectivity. The complex of the bis(intercalating) ligand also showed significantly lower DNA binding affinity than the free ligand, but in this case there was no attenuation of cytotoxicity.
An in vitro transcription assay was used to probe the sequence specificity of the binding of phenazine-tethered platinum complexes to DNA. It was found that when compared to cis-dichloro(ethylenediamine)platinum(II), the number of RNA polymerase blockage sites was increased by approximately 50% and the blockage sites were broadened by 1-3 nucleotides by the presence of the phenazine ligand. The rate of platination was also enhanced by the presence of the intercalator, and the increase in the kinetics of platination resulted in increased levels of adducts formed (i.e. high drug occupancy) as detected under conditions of active transcription. The level of platination by derivative 3 was 20-fold greater than that of the reference compound, which lacked a tethered intercalating phenazine group.
Site-specific degradation of DNA was achieved by the use of DNA oligonucleotides covalently tethered to phenazine 5,10-di-N-oxide. When annealed to a complementary DNA target strand, the antisense oligonucleotide effected alkylation of guanosine residues in proximity to the phenazine di-N-oxide prosthetic group. Admixture of dithiothreitol to the formed duplex resulted in reductive activation of the phenazine di-N-oxide moiety with concomitant generation of diffusible oxygen radicals; the latter effected strand scission of the target DNA oligonucleotide. Several parameters of DNA degradation were studied, including the effect on DNA degradation of chain length in the tether connecting the oligonucleotides and prosthetic group, the relative efficiencies of DNA cleavage when the prosthetic group was in the middle or at the end of the antisense oligonucleotide, and the effect of O2 on DNA degradation. Also studied was the actual chemistry of DNA oligonucleotide degradation and the ability of individual diastereomers of the modified oligonucleotides to mediate degradation of the target DNA.
The effects of dichloroacetate and phenazine methosulphate on the content of fructose-2,6-bisphosphate and glycogenesis in incubated epididymal adipose tissue were examined. Both agents stimulated the synthesis of fructose-2,6-bisphosphate in the presence of glucose, the effect being higher in tissue from fasted-refed rats than in normal fed rats. Additions of dichloroacetate to the incubation medium also increased the incorporation of [U-14C]glucose into glycogen and this effect was additive with that of insulin. However phenazine methosulphate strongly depressed the insulin-dependent glycogen synthesis. These data are considered in relation to the increased rate of glucose metabolism known to occur in the presence of dichloroacetate and the stimulation of pentose phosphate pathway with phenazine methosulphate.
Radical-anions, electrochemically generated in aprotic solvent from C(2) symmetric homochiral phenazine derivatives, act as chiral electrogenerated bases (EGBs) in the desymmetrisation by selective deprotonation of a prochiral epoxide (3,4-epoxy-2,3,4,5-tetrahydrothiophene-1,1-dioxide); the anion produced is trapped by mesitoic anhydride. The phenazines may be recovered in high yield by air oxidation. Enantiomeric excesses are modest (8-34%) but this is to our knowledge the first demonstration of such stereoselective electrochemically-initiated deprotonation. The reactivity of phenazine radical-anions as EGBs has also been explored by measurements of the rates of proton transfer; the prochiral epoxide was found to have a kinetic acidity similar to that of the methyltriphenylphosphonium cation.
Pseudomonas aeruginosa and Klebsiella pneumoniae are Gram-negative opportunistic pathogens that frequently colonize the human body and are major causes of infection. These bacteria are often co-isolated in polymicrobial urinary tract and lung infections, the latter of which is associated with increased disease severity and worse clinical outcomes. Despite their overlapping niches and clinical relevance, little is known about how these two pathogens interact and how those interactions influence human health. Given the growing recognition that microbial interactions are key drivers of disease, we investigated how P. aeruginosa and K. pneumoniae influence one another. We discovered an antagonistic interaction in which P. aeruginosa restricts the growth of K. pneumoniae. This inhibition is driven by phenazine production in P. aeruginosa, specifically the secondary metabolites pyocyanin and pyorubin, which are both necessary and sufficient to suppress K. pneumoniae growth. Using a diverse set of clinical isolates, we found that this antagonism is strain dependent. Both the susceptibility of K. pneumoniae to phenazines and the ability of P. aeruginosa to restrict K. pneumoniae growth varies between strains. Moreover, the necessity of phenazine production is specific to the site of infection. Together, these findings demonstrate that strain background and environmental context are critical determinants of pathogen interactions. Our work underscores the importance of considering these variables when investigating how microbial interactions influence infection and disease outcomes.
Pyocyanin, phenazine-1-carboxylic acid and more than 70 related compounds collectively known as phenazines are produced by various species of Pseudomonas, including the fluorescent pseudomonad P. aeruginosa, a Gram-negative opportunistic pathogen in humans and animals. P. aeruginosa synthesizes a characteristic blue water-soluble compound called pyocyanin (1-hydroxy-5-methyl-phenazine). Two enzymes designated PhzM and PhzS are involved in the terminal steps of its synthesis and very little is known about these enzymes. In this study, PhzM, a dimeric S-adenosylmethionine-dependent methyltransferase, was purified and crystallized from PEG 3350/sodium cacodylate/sodium citrate pH 6.5. The crystals belong to space group P1, with unit-cell parameters a = 46.1, b = 61.8, c = 69.6 A, alpha = 96.3, beta = 106.6, gamma = 106.9 degrees . They contain one dimer in the asymmetric unit and diffract to a resolution of 1.8 A. Anomalous data to 2.3 A resolution have been collected from seleno-L-methionine-labelled PhzM.
Pseudomonas fluorescens 2-79 and P. aureofaciens 30-84 produce the antibiotic phenazine-1-carboxylic acid and suppress take-all, an important root disease of wheat caused by Gaeumannomyces graminis var. tritici. To determine whether the antibiotic is produced in situ, wheat seeds were treated with strain 2-79 or 30-84 or with phenazine-nonproducing mutants or were left untreated and then were sown in natural or steamed soil in the field or growth chamber. The antibiotic was isolated only from roots of wheat colonized by strain 2-79 or 30-84 in both growth chamber and field studies. No antibiotic was recovered from the roots of seedlings grown from seeds treated with phenazine-nonproducing mutants or left untreated. In natural soils, comparable amounts of antibiotic (27 to 43 ng/g of root with adhering soil) were recovered from roots colonized by strain 2-79 whether or not the pathogen was present. Roots of plants grown in steamed soil yielded larger bacterial populations and more antibiotic than roots from natural soils. In steamed and natural soils, roots from which the antibiotic was recovered had significantly less disease than roots with no antibiotic, indicating that suppression of take-all is related directly to the presence of the antibiotic in the rhizosphere.
Human polymorphonuclear leukocytes (PMNL) metabolize the potent chemotaxin leukotriene B4 (LTB4) by omega-oxidation to 20-hydroxyl-LTB4 and 20-carboxy-LTB4. The ability of unstimulated human PMNL to metabolize exogenous LTB4 was found to be inhibited by pyocyanin, a phenazine derivative produced by Pseudomonas aeruginosa, in a dose-dependent manner. 1-Hydroxyphenazine (1-OHP), a metabolite of pyocyanin, was not inhibitory under identical conditions. The initial enzymic step in the conversion of LTB4 is catalyzed by an NADPH-dependent cytochrome, P-450. Reduction of the phenazine derivatives by NADPH was measured spectrophotometrically. Pyocyanin was reduced by NADPH in vitro in a pH-dependent manner, while 1-OHP was poorly or negligibly reduced under similar conditions. Formation of NADP+ was 20.3 +/- 1.8 nmol min-1 for pyocyanin (10 microM) at pH 5.5, compared with 0.6 +/- 0.2 nmol min-1 for 1-OHP (10 microM), while at pH 7.5 a value of 2.2 +/- 1.3 nmol min-1 was obtained for pyocyanin, with no detectable activity for 1-OHP. This indicates that inhibition of LTB4 omega-hydroxylase activity by pyocyanin might be achieved by competition for NADPH. Incorporation of exogenous 5-hydroxyeicosatetraenoic acid by PMNL into lipid pools was not affected by either phenazine derivative. The ability of bacterial pyocyanin to limit the omega-oxidation of LTB4 may have important implications for PMNL LTB4 receptor status and chemotaxis in vivo.
The lipophilicity and membrane-destabilizing activities of clofazimine and three tetramethyl-piperidine (TMP)-substituted phenazines were compared with the anti-tumor and multiple drug resistance (MDR) neutralizing potential of these agents using a P-glycoprotein (P-gp)-expressing small cell lung cancer cell line (H69/LX4). Partition coefficients were measured as an index of lipophilicity, while membrane-destabilizing potential was measured using a conventional hemolytic assay. The membrane-destabilizing potential of the TMP-substituted phenazines was found to correlate positively with the degree of lipophilicity, as well as with MDR reversal activity. The presence of a TMP group, as well as chlorine atoms on the phenyl and anilino rings of these agents contributed to the enhancement of anti-tumor activity by potentiating membrane-destabilizing activity. TMP-substituted phenazines may be useful in the design of novel anti-cancer and MDR reversal agents.
Streptomyces cinnamonensis DSM 1042 produces two classes of secondary metabolites of mixed isoprenoid/nonisoprenoid origin: the polyketide-isoprenoid compound furanonaphthoquinone I (FNQ I) and several prenylated phenazines, predominantly endophenazine A. We now report the cloning and sequence analysis of a 55 kb gene cluster required for the biosynthesis of these compounds. Several inactivation experiments confirmed the involvement of this gene cluster in the biosynthesis of FNQ I and endophenazine A. The six identified genes for endophenazine biosynthesis showed close similarity to phenazine biosynthetic genes from Pseudomonas. Of the 28 open reading frames identified in the adjacent FNQ I cluster, 13 showed close similarity to genes contained in the cluster for furaquinocin-a structurally similar metabolite from another Streptomyces strain. These genes included a type III polyketide synthase sequence, a momA-like monooxygenase gene, and two cloQ-like prenyltransferase genes designated fnq26 and fnq28. Inactivation experiments confirmed the involvement of fnq26 in FNQ I biosynthesis, whereas no change in secondary-metabolite formation was observed after fnq28 inactivation. The FNQ I cluster contains a contiguous group of five genes, which together encode all the enzymatic functions required for the recycling of S-adenosylhomocysteine (SAH) to S-adenosylmethionine (SAM). Two SAM-dependent methyltransferases are encoded within the cluster. Inactivation experiments showed that fnq9 is responsible for the 7-O-methylation and fnq27 for the 6-C-methylation reaction in FNQ I biosynthesis.
1,9-Phenazine-bis(dialkylaminocarboxamides) were prepared for screening as potential antimalarials. No significant activity against Plasmodium berghei was observed. The phenazine targets were prepared from 1,9-phenazinedicarboxylic acid by standard methods. The reaction between 1,9-phenazinedicarboxylic acid and thionyl chloride in the presence of dimethylformamide unexpectedly gave 4-chloro-1,9-phenazinedicarbonyl chloride.
The bacterial strain GC-B26, which showed strong antifungal and anti-oomycete activity against some plant pathogens, was isolated from a grassland soil in Korea. Based on morphological, physiological and biochemical characteristics, GC-B26 was identical to Pseudomonas aeruginosa (Schroeter) Migula. The antibiotic G26A, active against Phytophthora capsici Leonian and Colletotrichum orbiculare (Berk & Mont) van Arx, was isolated from the culture filtrates of Ps aeruginosa strain GC-B26 using various chromatographic procedures. The EI mass and UV spectral results indicated that G26A is an analogue of phenazines, having molecular formula C13H8N2O2 (M+, m/z 224.0664). On the basis of NMR spectral data, G26A was confirmed as phenazine-1-carboxylic acid. C orbiculare, P capsici and Pythium ultimum Trow were most sensitive to G26A, with MIC values of approximately 5 microg ml(-1). However, no antimicrobial activity was found against yeasts and bacteria, even at a concentration of over 100 microg ml(-1). Treatment with the antibiotic gave highly significant protective activity against the development of Phytophthora disease on pepper and anthracnose on cucumber plants. The disease control efficacy was only slightly less than that of the commercial fungicides metalaxyl and chlorothalonil.