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PubMed1988

Oxidation of substituted phenols by Pseudomonas putida F1 and Pseudomonas sp. strain JS6.

The biodegradation of benzene, toluene, and chlorobenzenes by Pseudomonas putida involves the initial conversion of the parent molecules to cis-dihydrodiols by dioxygenase enzyme systems. The cis-dihydrodiols are then converted to the corresponding catechols by dihydrodiol dehydrogenase enzymes. Pseudomonas sp. strain JS6 uses a similar system for growth on toluene or dichlorobenzenes. We tested the wild-type organisms and a series of mutants for their ability to transform substituted phenols after induction with toluene. When grown on toluene, both wild-type organisms converted methyl-, chloro-, and nitro-substituted phenols to the corresponding catechols. Mutant strains deficient in dihydrodiol dehydrogenase or catechol oxygenase activities also transformed the phenols. Oxidation of phenols was closely correlated with the induction and activity of the toluene dioxygenase enzyme system.

Biodegradation, Environmental↗
PubMed1989

Identification of Pseudomonas alcaligenes chromosomal DNA in the plasmid DNA of the chlorobenzene-degrading recombinant Pseudomonas putida strain CB1-9.

The recombinant Pseudomonas putida strain CB1-9, which acquired the ability to grow on chlorobenzenes, contains a 33-kilobase (kb) plasmid (pKFL3) which lacked homology to an indigenous 15-kb plasmid (pKFL1) in Pseudomonas alcaligenes C-0 parent but was homologous to a 55-kb plasmid (pKFL2) from the P. putida R5-3 parent. Chromosomal DNA of P. alcaligenes C-0 hybridized to probes prepared from pKFL3 but not to probes prepared from pKFL2. A single clone from a genomic library of P. alcaligenes C-0 hybridized to EcoRI-digested pKFL3. Southern blot hybridization with the insert DNA from that clone identified homology with specific restriction enzyme fragments in pKFL3. The ability of the recombinant to utilize 3-chlorobenzoate, chlorobenzene, and 1,4-dichlorobenzene as well as its loss of utilization of xylenes and methylbenzoates appears to be associated with the transfer and integration of chromosomal DNA from P. alcaligenes into a Tol-like plasmid of P. putida R5-3.

Blotting, Southern↗
PubMed1968

Metabolism of tryptophans by Pseudomonas aureofaciens. VI. Production of pyrrolnitrin by selected Pseudomonas species.

Twenty-nine strains of Pseudomonas, classified as P. fluorescens biotype D or E or as P. multivorans, were examined for the production of pyrrolnitrin, an antifungal agent synthesized in P. aureofaciens. Eight strains were shown to produce pyrrolnitrin in shake-flask fermentation. Four cultures were from the multivorans taxon, and the remaining four were members of the fluorescens group. The antifungal agent produced in these strains was isolated and shown to be pyrrolnitrin by comparison with an authentic sample. The strains differed markedly with respect to the amount of pyrrolnitrin produced and in their utilization of exogenous tryptophan. Secondary metabolites, not related to pyrrolnitrin, were also examined and compared with those synthesized in P. aureofaciens. Marked differences were noted in both phenazine pigments and phenolic metabolites. The results of the study suggest that the production of pyrrolnitrin may be widespread in selected taxonomic groups of Pseudomonas.

Antifungal Agents↗
PubMed2005

Solubility and bioactivity of the Pseudomonas quinolone signal are increased by a Pseudomonas aeruginosa-produced surfactant.

Pseudomonas aeruginosa is a gram-negative bacterium that causes serious infections in immunocompromised individuals and cystic fibrosis patients. This opportunistic pathogen controls many of its virulence factors and cellular functions through the activity of three cell-to-cell signals, N-(3-oxododecanoyl)-L-homoserine lactone, N-butyryl-L-homoserine lactone, and the Pseudomonas quinolone signal (PQS). The activity of these signals is dependent upon their ability to dissolve in and freely diffuse through the aqueous solution in which P. aeruginosa happens to reside. Despite this, our data indicated that PQS was relatively insoluble in aqueous solutions, which led us to postulate that P. aeruginosa could be producing a PQS-solubilizing factor. In this report, we show that the P. aeruginosa-produced biosurfactant rhamnolipid greatly enhances the solubility of PQS in aqueous solutions. The enhanced solubility of PQS led to an increase in PQS bioactivity, as measured by both a gene induction assay and an apoptosis assay. This is the first demonstration of the importance of a bacterial surfactant in the solubilization and bioactivity of a cell-to-cell signal.

Apoptosis↗
PubMed2006

RhlR expression in Pseudomonas aeruginosa is modulated by the Pseudomonas quinolone signal via PhoB-dependent and -independent pathways.

The expression of virulence determinants in Pseudomonas aeruginosa is coordinately regulated in response to both the social environment--commonly referred to as quorum sensing--and to environmental cues. In this study we have dissected the various independent regulation levels for pyocyanin production, which is influenced by the homoserine lactone- and Pseudomonas quinolone signal (PQS)-mediated quorum-sensing systems as well as by iron and phosphate availability. We demonstrate that the phosphate regulon is involved in the transcriptional activation of rhlR and the augmentation of PQS and pyocyanin production under phosphate limitation. However, we also observed an enhancement of rhlR transcription under low-iron medium conditions and after the addition of PQS that was independent of the phosphate regulon. These results highlight the complexity of secondary metabolite production in P. aeruginosa via environmental cues and the quorum-sensing system.

4-Butyrolactone↗
PubMed1970

Nucleic acid similarities among Pseudomonas pseudomallei, Pseudomonas multivorans, and Actinobacillus mallei.

Annealing experiments on membrane filters were carried out with deoxyribonucleic acids (DNA) from selected strains of the nomen-species of Pseudomonas, Actinobacillus, Chromobacterium, and Micrococcus, with the use of DNA of Pseudomonas pseudomallei and Actinobacillus mallei as reference materials. Under the usual conditions employed in these experiments, the results were not quantitatively reproducible. Incorporation of dimethylsulfoxide (DMSO) into the incubation medium greatly increased differences in comparative binding. DNA binding in agar matrices was examined in the presence and absence of DMSO at various incubation temperatures. It was found that the greatest specificity, stability, and total binding for DNA containing high amounts of guanine and cytosine occurred in the presence of DMSO. Under the most stringent annealing conditions permitted in agar, DNA species from P. pseudomallei and A. mallei in the presence of DMSO demonstrated interspecific relative bindings of 76 to 86% when compared to the homologous reactions. The thermal elution midpoints (E(m)) of these duplexed interspecific DNA species were quite close to the homologous E(m) values. The relative bindings of P. multivorans DNA types to either reference DNA ranged between 6 to 27%, and the E(m) values were 4 to 7 C less than those for the homologous reactions.

Actinobacillus↗
PubMed1990

Inhibition by Agrobacterium tumefaciens and Pseudomonas savastanoi of development of the hypersensitive response elicited by Pseudomonas syringae pv. phaseolicola.

Injection into tobacco leaves of biotype 1 Agrobacterium tumefaciens or of Pseudomonas savastanoi inhibited the development of a visible hypersensitive response to the subsequent injection at the same site of Pseudomonas syringae pv. phaseolicola. This interference with the hypersensitive response was not seen with injection of bacterial growth medium or Escherichia coli cells. Live A. tumefaciens cells were required for the inhibitory effect. Various mutants and strains of A. tumefaciens were examined to determine the genes involved. Known chromosomal mutations generally had no effect on the ability of A. tumefaciens to inhibit the hypersensitive response, except for chvB mutants which showed a reduced (but still significant) inhibition of the hypersensitive response. Ti plasmid genes appeared to be required for the inhibition of the hypersensitive response. The bacteria did not need to be virulent in order to inhibit the hypersensitive response. Deletion of the vir region from pTi had no effect on the inhibition. However, the T region of the Ti plasmid was required for inhibition. Studies of transposon mutants suggested that the tms but not tmr or ocs genes were required. These genes were not acting after transfer to plant cells since they were effective in strains lacking vir genes and thus unable to transfer DNA to plant cells. The results suggest that the expression of the tms genes in the bacteria may inhibit the development of the hypersensitive response by the plant. An examination of the genes required in P. savastanoi for the inhibition of the hypersensitive response suggested that bacterial production of auxin was also required for the inhibition of the hypersensitive response by these bacteria.

Escherichia coli↗
PubMed1992

Characterization of Pseudomonas putida mutants unable to catabolize benzoate: cloning and characterization of Pseudomonas genes involved in benzoate catabolism and isolation of a chromosomal DNA fragment able to substitute for xylS in activation of the TOL lower-pathway promoter.

Mutants of Pseudomonas putida mt-2 that are unable to convert benzoate to catechol were isolated and grouped into two classes: those that did not initiate attack on benzoate and those that accumulated 3,5-cyclohexadiene-1,2-diol-1-carboxylic acid (benzoate diol). The latter mutants, represents by strain PP0201, were shown to lack benzoate diol dehydrogenase (benD) activity. Mutants from the former class were presumed either to carry lesions in one or more subunit structural genes of benzoate dioxygenase (benABC) or the regulatory gene (benR) or to contain multiple mutations. Previous work in this laboratory suggested that benR can substitute for the TOL plasmid-encoded xylS regulatory gene, which promotes gene expression from the OP2 region of the lower or meta pathway operon. Accordingly, structural and regulatory gene mutations were distinguished by the ability of benzoate-grown mutant strains to induce expression from OP2 without xylS by using the TOL plasmid xylE gene (encoding catechol 2,3-dioxygenase) as a reporter. A cloned 12-kb BamHI chromosomal DNA fragment from the P. aeruginosa PAO1 chromosome complemented all of the mutations, as shown by restoration of growth on benzoate minimal medium. Subcloning and deletion analyses allowed identification of DNA fragments carrying benD, benABC, and the region possessing xylS substitution activity, benR. Expression of these genes was examined in a strain devoid of benzoate-utilizing ability, Pseudomonas fluorescens PFO15. The disappearance of benzoate and the production of catechol were determined by chromatographic analysis of supernatants from cultures grown with casamino acids. When P. fluorescens PFO15 was transformed with plasmids containing only benABCD, no loss of benzoate was observed. When either benR or xylS was cloned into plasmids compatible with those plasmids containing only the benABCD regions, benzoate was removed from the medium and catechol was produced. Regulation of expression of the chromosomal structural genes by benR and xylS was quantified by benzoate diol dehydrogenase enzyme assays. The results obtained when xylS was substituted for benR strongly suggest an isofunctional regulatory mechanism between the TOL plasmid lower-pathway genes (via the OP2 promoter) and chromosomal benABC. Southern hybridizations demonstrated that DNA encoding the benzoate dioxygenase structural genes showed homology to DNA encoding toluate dioxygenase from the TOL plasmid pWW0, but benR did not show homology to xylS. Evolutionary relationships between the regulatory systems of chromosomal and plasmid-encoded genes for the catabolism of benzoate and related compounds are suggested.

Benzoates↗
PubMed1998

Chromosomal integration, tandem amplification, and deamplification in Pseudomonas putida F1 of a 105-kilobase genetic element containing the chlorocatechol degradative genes from Pseudomonas sp. Strain B13.

Analysis of chlorobenzene-degrading transconjugants of Pseudomonas putida F1 which had acquired the genes for chlorocatechol degradation (clc) from Pseudomonas sp. strain B13 revealed that the clc gene cluster was present on a 105-kb amplifiable genetic element (named the clc element). In one such transconjugant, P. putida RR22, a total of seven or eight chromosomal copies of the entire genetic element were present when the strain was cultivated on chlorobenzene. Chromosomal integrations of the 105-kb clc element occurred in two different loci, and the target sites were located within the 3' end of glycine tRNA structural genes. Tandem amplification of the clc element was preferentially detected in one locus on the F1 chromosome. After prolonged growth on nonselective medium, transconjugant strain RR22 gradually diverged into subpopulations with lower copy numbers of the clc element. Two nonadjacent copies of the clc element in different loci always remained after deamplification, but strains with only two copies could no longer use chlorobenzene as a sole substrate. This result suggests that the presence of multiple copies of the clc gene cluster was a prerequisite for the growth of P. putida RR22 on chlorobenzene and that amplification of the element was positively selected for in the presence of chlorobenzene.

Base Sequence↗
PubMed2000

The Pseudomonas quinolone signal regulates rhl quorum sensing in Pseudomonas aeruginosa.

The opportunistic pathogen Pseudomonas aeruginosa uses intercellular signals to control the density-dependent expression of many virulence factors. The las and rhl quorum-sensing systems function, respectively, through the autoinducers N-(3-oxododecanoyl)-L-homoserine lactone and N-butyryl-L-homoserine lactone (C(4)-HSL), which are known to positively regulate the transcription of the elastase-encoding gene, lasB. Recently, we reported that a second type of intercellular signal is involved in lasB induction. This signal was identified as 2-heptyl-3-hydroxy-4-quinolone and designated the Pseudomonas quinolone signal (PQS). PQS was determined to be part of the quorum-sensing hierarchy since its production and bioactivity depended on the las and rhl quorum-sensing systems, respectively. In order to define the role of PQS in the P. aeruginosa quorum-sensing cascade, lacZ gene fusions were used to determine the effect of PQS on the transcription of the quorum-sensing system genes lasR, lasI, rhlR, and rhlI. We found that in P. aeruginosa, PQS caused a major induction of rhlI'-lacZ and had lesser effects on the transcription of lasR'-lacZ and rhlR'-lacZ. We also observed that the transcription of both rhlI'-lacZ and lasB'-lacZ was cooperatively effected by C(4)-HSL and PQS. Additionally, we present data indicating that PQS was not produced maximally until cultures reached the late stationary phase of growth. Taken together, our results imply that PQS acts as a link between the las and rhl quorum-sensing systems and that this signal is not involved in sensing cell density.

4-Butyrolactone↗
PubMed2005

Regulation of Pseudomonas quinolone signal synthesis in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic lung infections in cystic fibrosis patients and is a major source of nosocomial infections. This bacterium controls many virulence factors by using two quorum-sensing systems, las and rhl. The las system is composed of the LasR regulator protein and its cell-to-cell signal, N-(3-oxododecanoyl) homoserine lactone, and the rhl system is composed of RhlR and the signal N-butyryl homoserine lactone. A third intercellular signal, the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4-quinolone), also regulates numerous virulence factors. PQS synthesis requires the expression of multiple operons, one of which is pqsABCDE. Previous experiments showed that the transcription of this operon, and therefore PQS production, is negatively regulated by the rhl quorum-sensing system and positively regulated by the las quorum-sensing system and PqsR (also known as MvfR), a LysR-type transcriptional regulator protein. With the use of DNA mobility shift assays and beta-galactosidase reporter fusions, we have studied the regulation of pqsR and its relationship to pqsA, lasR, and rhlR. We show that PqsR binds the promoter of pqsA and that this binding increases dramatically in the presence of PQS, implying that PQS acts as a coinducer for PqsR. We have also mapped the transcriptional start site for pqsR and found that the transcription of pqsR is positively regulated by lasR and negatively regulated by rhlR. These results suggest that a regulatory chain occurs where pqsR is under the control of LasR and RhlR and where PqsR in turn controls pqsABCDE, which is required for the production of PQS.

Bacterial Proteins↗
PubMed1975

Cultural and biochemical characteristics and fatty acid composition of Pseudomonas diminuta and Pseudomonas vesiculare.

The cultural characteristics, biochemical activity, and cellular fatty acid composition of Pseudomonas diminuta and Pseudomonas vesiculare provided means for differentiation of these closely related species. Broth cultures of P. diminuta showed turbid growth and a distinct surface pellicle after 24 h at 35 C. P. vesiculare had no pellicle, and only light, diffuse growth was observed. All strains of P. vesiculare oxidized maltose and hydrolyzed esculin to varying degrees; P. diminuta was negative in these tests. The cellular fatty acids of these two species were similar, except that P. diminuta possessed a C19 cyclopropane acid which was not detected in P. vesiculare.

Esculin↗
PubMed1971

Interaction of Pseudomonas bacteriophage 2 with the slime polysaccharide and lipopolysaccharide of Pseudomonas aeruginosa strain B1.

Purified slime polysaccharide B and lipopolysaccharide of Pseudomonas aeruginosa strain BI were shown to possess receptor-like properties in inactivating Pseudomonas phage 2, whereas lipoprotein and glycopeptide fractions were devoid of activity. On a weight basis, slime polysaccharide B was more effective than lipopolysaccharide in inactivating phage. The specificity of the reaction with slime polysaccharide B was indicated by the fact that slime polysaccharide A of P. aeruginosa strain EI failed to inactivate phage 2. Electron micrographs showed phage 2 in typical, tail-first position of attachment on intact cells of strain BI, slime polysaccharide B, and lipopolysaccharide. Tail fibers were discernible during phage attachment.

Adsorption↗
PubMed2004

Mutagenic DNA repair potential in Pseudomonas spp., and characterization of the rulABPc operon from the highly mutable strain Pseudomonas cichorii 302959.

We assessed the tolerance to ultraviolet B (UVB; 290-320 nm) radiation and UVB-induced mutability in 28 Pseudomonas spp. and four Burkholderia cepacia strains. The UVB survival of 23 (72%) of the strains was elevated (>46% survival following irradiation with a 2250 J m-2 dose), and 17 (53%) strains were defined as mutable by UVB. A mutagenic DNA repair determinant was cloned and characterized from the highly mutable strain P. cichorii 302959 and shown by sequence analysis to be an allele of rulAB, a mutagenic DNA repair determinant previously characterized from Pseudomonas syringae. Phylogenetic analyses of RulA- and RulB-related sequences indicated that the sequences identified in environmental bacteria shared a common ancestor with UmuDC-like sequences from enteric bacteria but were considerably diverged. The dynamics of UVB-induced mutability to nalidixic acid resistance (NalR) and rifampicin resistance (RifR) were studied in replicate populations of P. cichorii 302959 subjected to a daily UVB dose of 2250 J m-2 for 14 consecutive days. While there was an initial spike in the frequency of NalR and RifR mutants recovered on Days 1 and 2 of two separate experiments, the frequencies were sharply reduced and then fluctuated throughout the duration of both experiments. These experimental results are intriguing because they point to the possibility that P. cichorii possesses additional mechanisms to curtail the induction of spontaneous mutants following repeated episodes of UVB irradiation.

Anti-Infective Agents↗
PubMedDate not supplied

Verapamil-tobramycin synergy in Pseudomonas cepacia but not Pseudomonas aeruginosa in vitro.

Virtually all patients with cystic fibrosis (CF) die of respiratory failure resulting from chronic progressive pulmonary infections. Pseudomonas aeruginosa and Pseudomonas (Burkholderia) cepacia are the two major bacterial pathogens responsible for the pulmonary deterioration in these patients. Tobramycin has variable inhibitory effects on these organisms, but in many isolates this inhibition is increased in vitro by exposure to the diuretic, amiloride. Aerosolized amiloride has been shown to be of clinical benefit in CF. The basis for this synergy is unknown. To examine the possibility that amiloride-tobramycin synergy is mediated through a bacterial efflux mechanism mediated by a multidrug resistant (mdr) protein, we studied the inhibitory effect of verapamil, a known mdr inhibitor on the tobramycin MIC in P. aeruginosa and P. cepacia using standard MIC and synergy testing. Verapamil had no effect on the tobramycin MIC in P. aeruginosa but was able to act synergistically with tobramycin in reducing the tobramycin MIC markedly in all isolates of P. cepacia tested. This combination of drugs may be worth studying as a new treatment strategy for resistant P. cepacia infections.

Burkholderia cepacia↗
PubMed1992

Interaction of the Pseudomonas aeruginosa secretory products pyocyanin and pyochelin generates hydroxyl radical and causes synergistic damage to endothelial cells. Implications for Pseudomonas-associated tissue injury.

Pyocyanin, a secretory product of Pseudomonas aeruginosa, has the capacity to undergo redox cycling under aerobic conditions with resulting generation of superoxide and hydrogen peroxide. By using spin trapping techniques in conjunction with electron paramagnetic resonance spectrometry (EPR), superoxide was detected during the aerobic reduction of pyocyanin by NADH or porcine endothelial cells. No evidence of hydroxyl radical formation was detected. Chromium oxalate eliminated the EPR spectrum of the superoxide-derived spin adduct resulting from endothelial cell exposure to pyocyanin, suggesting superoxide formation close to the endothelial cell plasma membrane. We have previously reported that iron bound to the P. aeruginosa siderophore pyochelin (ferripyochelin) catalyzes the formation of hydroxyl free radical from superoxide and hydrogen peroxide via the Haber-Weiss reaction. In the present study, spin trap evidence of hydroxyl radical formation was detected when NADH and pyocyanin were allowed to react in the presence of ferripyochelin. Similarly, endothelial cell exposure to pyocyanin and ferripyochelin also resulted in hydroxyl radical production which appeared to occur in close proximity to the cell surface. As assessed by 51Cr release, endothelial cells which were treated with pyocyanin or ferripyochelin alone demonstrated minimal injury. However, endothelial cell exposure to the combination of pyochelin and pyocyanin resulted in 55% specific 51Cr release. Injury was not observed with the substitution of iron-free pyochelin and was diminished by the presence of catalase or dimethyl thiourea. These data suggest the possibility that the P. aeruginosa secretory products pyocyanin and pyochelin may act synergistically via the generation of hydroxyl radical to damage local tissues at sites of pseudomonas infection.

Animals↗
PubMed2000

Effect of C:N molar ratio on monomer composition of polyhydroxyalkanoates produced by Pseudomonas mendocina 0806 and Pseudomonas pseudoalkaligenus YS1.

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by bacteria. In this study, the effect of C:N molar ratio on the monomer composition of PHAs was investigated, including medium chain length PHA produced by Pseudomonas mendocina 0806 and PHA blends consisting of monomers of 3-hydroxybutyrate and medium chain length hydroxyalkanoate produced by Pseudomonas pseudoalkaligenus YS1. It was observed that there were some fixed ranges of C:N molar ratio that affect the monomer composition of PHA independently of the substrate. For strain 0806, the ranges were C:N < 20, 20 < C:N < 200, and C:N > 200. The monomer composition was constant among these ranges when using glucose and octanoate as the sole substrate. For strain YS1, the ranges were C:N < 20, 20 < C:N < 45, and C:N > 45. These results are useful for controlling monomer composition in PHA production.

3-Hydroxybutyric Acid↗