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1.
Sebat JL Paszczynski AJ Cortese MS Crawford RL 《Applied and environmental microbiology》2001,67(9):3934-3942
Pyridine-2,6-dithiocarboxylic acid (pdtc) is a metal chelator produced by Pseudomonas spp. It has been shown to be involved in the biodegradation of carbon tetrachloride; however, little is known about its biological function. In this study, we examined the antimicrobial properties of pdtc and the mechanism of its antibiotic activity. The growth of Pseudomonas stutzeri strain KC, a pdtc-producing strain, was significantly enhanced by 32 microM pdtc. All nonpseudomonads and two strains of P. stutzeri were sensitive to 16 to 32 microM pdtc. In general, fluorescent pseudomonads were resistant to all concentrations tested. In competition experiments, strain KC demonstrated antagonism toward Escherichia coli. This effect was partially alleviated by 100 microM FeCl3. Less antagonism was observed in mutant derivatives of strain KC (CTN1 and KC657) which lack the ability to produce pdtc. A competitive advantage was restored to strain CTN1 by cosmid pT31, which restores pdtc production. pT31 also enhanced the pdtc resistance of all pdtc-sensitive strains, indicating that this plasmid contains elements responsible for resistance to pdtc. The antimicrobial effect of pdtc was reduced by the addition of Fe(III), Co(III), and Cu(II) and enhanced by Zn(II). Analyses by mass spectrometry determined that Cu(I):pdtc and Co(III):pdtc2 form immediately under our experimental conditions. Our results suggest that pdtc is an antagonist and that metal sequestration is the primary mechanism of its antimicrobial activity. It is also possible that Zn(II), if present, may play a role in pdtc toxicity. 相似文献
2.
Antimicrobial Properties of Pyridine-2,6-Dithiocarboxylic Acid, a Metal Chelator Produced by Pseudomonas spp. 总被引:2,自引:0,他引:2
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J. L. Sebat A. J. Paszczynski M. S. Cortese R. L. Crawford 《Applied microbiology》2001,67(9):3934-3942
Pyridine-2,6-dithiocarboxylic acid (pdtc) is a metal chelator produced by Pseudomonas spp. It has been shown to be involved in the biodegradation of carbon tetrachloride; however, little is known about its biological function. In this study, we examined the antimicrobial properties of pdtc and the mechanism of its antibiotic activity. The growth of Pseudomonas stutzeri strain KC, a pdtc-producing strain, was significantly enhanced by 32 μM pdtc. All nonpseudomonads and two strains of P. stutzeri were sensitive to 16 to 32 μM pdtc. In general, fluorescent pseudomonads were resistant to all concentrations tested. In competition experiments, strain KC demonstrated antagonism toward Escherichia coli. This effect was partially alleviated by 100 μM FeCl3. Less antagonism was observed in mutant derivatives of strain KC (CTN1 and KC657) which lack the ability to produce pdtc. A competitive advantage was restored to strain CTN1 by cosmid pT31, which restores pdtc production. pT31 also enhanced the pdtc resistance of all pdtc-sensitive strains, indicating that this plasmid contains elements responsible for resistance to pdtc. The antimicrobial effect of pdtc was reduced by the addition of Fe(III), Co(III), and Cu(II) and enhanced by Zn(II). Analyses by mass spectrometry determined that Cu(I):pdtc and Co(III):pdtc2 form immediately under our experimental conditions. Our results suggest that pdtc is an antagonist and that metal sequestration is the primary mechanism of its antimicrobial activity. It is also possible that Zn(II), if present, may play a role in pdtc toxicity. 相似文献
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Zawadzka AM Vandecasteele FP Crawford RL Paszczynski AJ 《Canadian journal of microbiology》2006,52(12):1164-1176
We have identified two types of siderophores produced by Pseudomonas, one of which has never before been found in the genus. Twelve strains of Pseudomonas stutzeri belonging to genomovars 1, 2, 3, 4, 5, and 9 produced proferrioxamines, the hydroxamate-type siderophores. Pseudomonas stutzeri JM 300 (genomovar 7) and DSM 50238 (genomovar 8) and Pseudomonas balearica DSM 6082 produced amonabactins, catecholate-type siderophores. The major proferrioxamines detected were the cyclic proferrioxamines E and D2. Pseudomonas stutzeri KC also produced cyclic (X1 and X2) and linear (G1 and G2a-c) proferrioxamines. Our data indicate that the catecholate-type siderophores belong to amonabactins P 750, P 693, T 789, and T 732. A mutant of P. stutzeri KC (strain CTN1) that no longer produced the secondary siderophore pyridine-2,6-dithiocarboxylic acid continued to produce all other siderophores in its normal spectrum. Siderophore profiles suggest that strain KC (genomovar 9) belongs to the proferrioxamine-producing P. stuzeri. Moreover, a putative ferrioxamine outer membrane receptor gene foxA was identified in strain KC, and colony hybridization showed the presence of homologous receptor genes in all P. stutzeri and P. balearica strains tested. 相似文献
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Sepúlveda-Torre L Huang A Kim H Criddle CS 《Journal of molecular microbiology and biotechnology》2002,4(2):151-161
Previously, we described the generation and initial characterization of four Tn5 mutants of Pseudomonas stutzeri strain KC with impaired ability to degrade carbon tetrachloride (Sepúlveda-Torres et al., 1999). In this study, we show cloning and sequencing of an 8.3 kbp region in which all four transposons were located. This fragment encodes eight potential genes and is located in the central part of the 25 kbp fragment recently identified by Lewis et al. (2000) and shown by them to be sufficient to confer carbon tetrachloride transformation capability upon other pseudomonads. The four transposon insertion mutants mapped in ORF's F and I designated by Lewis et al. (2000). This is consistent with the results by Lewis et al. (2000) that orfFis required for carbon tetrachloride degradation. We further established that orfl is required for CCl4 degradation since the three mutants in this ORF were unable to degrade carbon tetrachloride. We present our analysis of the gene and protein sequences from the 8.3 kbp region and propose a tentative model for the role of different genes in the synthesis and activity of pyridine-2,6-bis(thiocarboxylate) (PDTC), the secreted factor responsible for carbon tetrachloride dechlorination. We also found a putative promoter that overlaps with a Fur-box-like sequence in the region upstream of mutated genes. To test this putative promoter region and Fur-box, we generated and ligated DNA fragments containing wild-type and mutant Fur-boxes to a lacZ reporter. The wild-type fragment showed promoter activity that is regulated by the concentration of iron in the medium. Finally, we screened a selection of Pseudomonas strains, including P. putida DSMZ 3601--a strain known to produce PDTC--for the presence of the genes characterized in this study. None of the strains tested positive, suggesting that Pseudomonas stutzeri strain KC may possess a distinct biosynthetic pathway for PDTC production. 相似文献
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Large Pseudomonas phages isolated from barley rhizosphere 总被引:1,自引:0,他引:1
Abstract: Five bacteriophages infecting common fluorescent pseudomonads ( Pseudomonas fluorescens and Pseudomonas putida ) were isolated from barley rhizosphere soil. Morphological and molecular characteristics of the phages are described together with selected phage-host interactions. All phages belonged to the Myoviridae family with isometrical heads on contractile tails; 4 of them were unusually large and had complex protein and DNA profiles. The large phages had estimated genome sizes of 200 kb or more. Restriction enzyme analyses and DNA-DNA hybridizations showed that all isolates represented different phage species. None of the isolates were observed to establish lysogeny with the main host strain, P. putida MM1. The large phages multiplied slowly on their hosts, producing very small plaques; one-step growth experiments with one of the large phages (Psp 4) hence demonstrated a long latent period (2.5 h) and a very small burst size (10 particles). One of the large phages (Psp 3) was abundant in the rhizosphere (approx. 104 pfu g−1 soil) and had a particularly broad host range which extended to both fluorescent ( Pseudomonas aeruginosa, P. fluorescens, P. putida and Pseudomonas chlororaphis ) and non-fluorescent (Pseudomonas stutzeri) Pseudomonas spp. occurring in soil. The ecological importance of the large Pseudomonas phages must be further studied, but their slow multiplication rates suggested a possible mechanism of balanced phage-host co-existence in the rhizosphere. 相似文献
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The effect of one intraperitoneal injection of 1.33 ml of CCl4 per kg of fish was studied. Two experimental series were performed and studied for 10 days (with diluent) and 24 h (pure CCl4 ) periods. LDH, GOT, GPT, GR, GDH, CPK, G-6-Pase, and AlkPase were studied. The activity of all enzymes in blood increased: LDH (four times the control), GOT (two times), GPT (three times); they reached a maximal activity 12 h after injection of diluted CCl4 . The levels of some enzymes were also examined in the liver. With pure CCl4 , maximal enzyme activity in blood occurred earlier (6 h). A 6 to 10 times increase was observed for GOT, GPT, LDH, GR, and GDH. Histopathological observations were correlated with these enzymes studies.
An Aeromonas disease characterized by the destruction of the dermis, the exposure of the muscle, and by the presence of numerous petechiae in the liver enabled us to examine the relationships between naturally induced tissue damage and enzyme levels in blood. The levels of seven blood enzymes were determined and the most significant modifications were observed for LDH and CPK. which increased their concentration from 3 to 7 times respectively. A pyruvate saturation test demonstrated that LDH was probably from liver as it was observed after CCl4 poisoning. The contribution of such biochemical studies in fish research is evaluated. 相似文献
An Aeromonas disease characterized by the destruction of the dermis, the exposure of the muscle, and by the presence of numerous petechiae in the liver enabled us to examine the relationships between naturally induced tissue damage and enzyme levels in blood. The levels of seven blood enzymes were determined and the most significant modifications were observed for LDH and CPK. which increased their concentration from 3 to 7 times respectively. A pyruvate saturation test demonstrated that LDH was probably from liver as it was observed after CCl
9.
Valero A Begum M Hocking AD Marín S Ramos AJ Sanchis V 《Journal of applied microbiology》2008,105(2):372-379
Aims: To evaluate the impact of modified atmosphere packaging on in vitro growth of Aspergillus carbonarius and Aspergillus niger , and possible effects on ochratoxin A (OTA) biosynthesis.
Methods and Results: Ochratoxigenic isolates belonging to the species A. carbonarius and A. niger were grown on a synthetic grapejuice medium (SNM) and packaged in combinations of controlled O2 (1% and 5%) and CO2 levels (0% and 15%), and in air as a control. Colony diameters were recorded every 3 days up to 21 days, and OTA was analysed after 7, 14 and 21 days. The greatest reductions in mycelial growth rate were observed at 1% O2 followed by 1% O2 /15% CO2 , whereas 5% O2 stimulated the growth of all isolates. OTA production by A. carbonarius and A. niger isolates was minimized at 1% O2 /15% CO2 and 1% O2 , respectively, after 7 days of incubation. Maximal OTA accumulation after 7 days was observed for all isolates in the control pack and at 5% O2 .
Conclusions: Of the atmospheres tested, only 1% O2 combined with 15% CO2 consistently reduced fungal growth and OTA synthesis by A. carbonarius and A. niger .
Significance and Impact of the Study: Storage under modified atmospheres is unlikely to be suitable as the sole method for OTA minimization and grape preservation; other inhibitory factors are necessary. 相似文献
Methods and Results: Ochratoxigenic isolates belonging to the species A. carbonarius and A. niger were grown on a synthetic grapejuice medium (SNM) and packaged in combinations of controlled O
Conclusions: Of the atmospheres tested, only 1% O
Significance and Impact of the Study: Storage under modified atmospheres is unlikely to be suitable as the sole method for OTA minimization and grape preservation; other inhibitory factors are necessary. 相似文献
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Laurie E. Comstock Judith A. Johnson Jane M. Michalski J. Glenn Morris Jr & James B. Kaper 《Molecular microbiology》1996,19(4):815-826
Vibrio cholerae serogroup O139 Bengal is the first documented serogroup other than O1 to cause epidemic cholera. The O139 Bengal strains are very similar to V. cholerae serogroup O1 biotype El Tor strains. The major differences between the two serogroups are that O139 Bengal contains a distinct O antigen and produces a polysaccharide capsule. We previously described three Tn phoA mutants of O139 strain AI1837 which abolish both O antigen and capsule production. These Tn phoA insertions were mapped to a 21.5 kb Eco RI fragment of the O139 chromosome. We describe here the cloning and mapping of this 21.5 kb Eco RI fragment and it was shown to complement each of the mutants in trans to produce O antigen and capsule. The Eco RI fragment contains 13 kb of DNA that is specific to O139 and 8.5 kb of DNA that is common to O1 and O139. Sequence analysis of the 13 kb of O139-specific DNA revealed that it contains 11 open reading frames all of which are transcribed in the same direction. Eight of the 11 open reading frames are homologous to sugar biosynthesis genes from other organisms. Using extended polymerase chain reactions, we show that the extent of the DNA region in O139 that is not present in O1 is approximately 35kb. The site of insertion of this O139-specific DNA in the O1 chromosome was mapped to the rfb O1 region. We also demonstrate that O139 Bengal strain AI1837 contains a deletion of 22 kb that in serogroup O1 strains contains the rfb region. Therefore, O139 Bengal probably arose from an O1 strain that had undergone genetic rearrangements including deletion of the O1 rfb region and acquisition of a 35 kb region of DNA which encodes O139 surface polysaccharide. 相似文献
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Alzate-Marin Menarim G. Soares Baía Paula JR K. Almeida De Souza Da Costa E. Gonçalves De Barros & Moreira 《Journal of Phytopathology》2001,149(5):259-264
The inheritance of anthracnose resistance of the common bean ( Phaseolus vulgaris L.) differential cultivar G 2333 to Colletotrichum lindemuthianum races 73 and 89 was studied in crosses with the susceptible cultivar Rudá. The segregation ratios of 15 : 1 in the F2 and 3 : 1 in the backcrosses to Rudá indicate that for each of the races tested there are two independent resistance loci in G 2333. A random amplified polymorphic DNA (RAPD) molecular marker (OPH181200C ) linked in resistance to race 73 was identified in a BC3 F2:3 population derived from crosses between Rudá and G 2333. A RAPD molecular marker OPAS13950C , previously identified as linked to gene Co-42 , was also amplified in this population. Co-segregation analyses showed that these two markers are located at 5.6 (OPH181200C ) and 11.2 (OPAS13950C ) cM of the Co-42 gene. These markers were not present in BC1 F2:3 plants resistant to race 89 indicating that this population carries a different resistance gene. DNA amplification of BC1 F2:3 plants with RAPD molecular marker OPAB450C , previously identified as linked to gene Co-5 , indicated that this gene is present in this population. 相似文献
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Eva Marie Muehe Simone Gerhardt Bernhard Schink & Andreas Kappler 《FEMS microbiology ecology》2009,70(3):3-11
In order to assess the importance of nitrate-dependent Fe(II) oxidation and its impact on the growth physiology of dominant Fe oxidizers, we counted these bacteria in freshwater lake sediments and studied their growth physiology. Most probable number counts of nitrate-reducing Fe(II)-oxidizing bacteria in the sediment of Lake Constance, a freshwater lake in Southern Germany, yielded about 105 cells mL−1 of the total heterotrophic nitrate-reducing bacteria, with about 1% (103 cells mL−1 ) of nitrate-reducing Fe(II) oxidizers. We investigated the growth physiology of Acidovorax sp. strain BoFeN1, a dominant nitrate-reducing mixotrophic Fe(II) oxidizer isolated from this sediment. Strain BoFeN1 uses several organic compounds (but no sugars) as substrates for nitrate reduction. It also reduces nitrite, dinitrogen monoxide, and O2 , but cannot reduce Fe(III). Growth experiments with cultures amended either with acetate plus Fe(II) or with acetate alone demonstrated that the simultaneous oxidation of Fe(II) and acetate enhanced growth yields with acetate alone (12.5 g dry mass mol−1 acetate) by about 1.4 g dry mass mol−1 Fe(II). Also, pure cultures of Pseudomonas stutzeri and Paracoccus denitrificans strains can oxidize Fe(II) with nitrate, whereas Pseudomonas fluorescens and Thiobacillus denitrificans strains did not. Our study demonstrates that nitrate-dependent Fe(II) oxidation contributes to the energy metabolism of these bacteria, and that nitrate-dependent Fe(II) oxidation can essentially contribute to anaerobic iron cycling. 相似文献
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Walter G. Zumft Sandor Blümle Cornelia Braun Heinz Körner 《FEMS microbiology letters》1992,91(2):153-158
Abstract Chlorate-resistant mutants were generated by random insertion of the transposon Tn5 into genomic DNA of Pseudomonas stutzeri ZoBell strain and selected for loss of nitrate respiration (Nar phenotype). The mutants were differentiated by restriction-fragment analysis, by assaying for nitrate assimilation and for molybdenum co-factor activity, and by the amount of respiratory nitrate reductase. Two mutants, lacking both nitrate respiration and nitrate assimilation, over-produced an inactive nitrate reductase but synthesized in the presence of nitrate only a reduced amount of respiratory nitrite reductase (cytochrome cd 1 ). Expression of cytochrome cd 1 in these mutants was specifically induced by nitrate, suggesting a sensor system for this substrate. 相似文献
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Wilde C Mazel D Hochhut B Middendorf B Le Roux F Carniel E Dobrindt U Hacker J 《Molecular microbiology》2008,68(1):139-151
In uropathogenic Escherichia coli strain 536, six pathogenicity islands (PAIs) encode key virulence factors. All PAIs except PAI IV536 are flanked by direct repeats and four of them encode integrases responsible for their chromosomal excision. To study recombination sites used for the integration by PAI II536 and III536 integrases, we measured site-specific recombination between the chromosomal integration site attB , and the PAI-specific attachment site attP . We show that PAI III536 IntB, but not IntA, mediates PAI III536 integration. Studies of integrative recombination sites of both PAIs show that, when using a large cognate attP site (839 bp for PAI II536 and 268 bp for PAI III536 ), PAI II536 and III536 attB sites could be reduced to 16 bp and 20 bp, respectively, without affecting recombination. Further reduction to 14 bp for PAI II536 and 13 bp for PAI III536 diminished recombination efficiency. Surprisingly, attP sites could also be reduced to 14 bp (PAI II536 ) and 20 bp (PAI III536 ). The integration host factor (IHF) and the DNA-bending HU protein do not influence PAI II536 recombination, but IHF enhances PAI-III536 excision and negatively affects its integration. These data suggest that PAI intasomes differ from those of lambda and P4 integrase paradigms. 相似文献
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A. Hernandez-Mendoza D. Guzman-de-Peña H.S. Garcia 《Journal of applied microbiology》2009,107(2):395-403
Aims: To assess the ability of five probiotic bacteria to bind aflatoxin B1 and to determine the key role of teichoic acids in the binding mechanism.
Methods and Results: The strains were incubated in aqueous solutions containing aflatoxin B1 (AFB1 ). The amount of free toxin was quantified by HPLC. Stability of the bacteria–aflatoxin complex was evaluated by repeated washes with buffer. In order to understand the binding process, protoplasts, spheroplasts and cell wall components of two strains were analysed to assess their capacity to bind AFB1 . Additionally, the role of teichoic acids in the AFB1 binding process was assessed. Lactobacillus reuteri strain NRRL14171 and Lactobacillus casei strain Shirota were the most efficient strains for binding AFB1 . The stability of the AFB1 –bacteria complex appears to be related to the binding ability of a particular strain; AFB1 binding was also pH-dependent. Our results suggest that teichoic acids could be responsible for this ability.
Conclusions: Our results provide information concerning AFB1 binding by previously untested strains, leading to enhanced understanding of the mechanism by which probiotic bacteria bind AFB1 .
Significance and Impact of the Study: Our results support the suggestion that some probiotic bacteria could prevent absorption of aflatoxin from the gastrointestinal tract. 相似文献
Methods and Results: The strains were incubated in aqueous solutions containing aflatoxin B
Conclusions: Our results provide information concerning AFB
Significance and Impact of the Study: Our results support the suggestion that some probiotic bacteria could prevent absorption of aflatoxin from the gastrointestinal tract. 相似文献
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Cells of Geobacter metallireducens , Magnetospirillum strain AMB-1, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswaldense showed N2 -dependent growth, the first anaerobically with Fe(III) as the electron acceptor, and the latter three species microaerobically in semi-solid oxygen gradient cultures. Cells of the Magnetospirillum species grown with N2 under microaerobic conditions were magnetotactic and therefore produced magnetosomes. Cells of Geobacter metallireducens reduced acetylene to ethylene (11.5 ± 5.9 nmol C2 H4 produced min−1 mg−1 cell protein) while growing with Fe(III) as the electron acceptor in anaerobic growth medium lacking a fixed nitrogen source. Cells of the Magnetospirillum species, grown in a semi-solid oxygen gradient medium, also reduced acetylene at comparable rates. Uncut chromosomal and fragments from endonuclease-digested chromosomal DNA from these species, as well as Geobacter sulphurreducens organisms, hybridized with a nifHDK probe from Rhodospirillum rubrum , indicating the presence of these nitrogenase structural genes in these organisms. The evidence presented here shows that members of the metal-metabolizing genera, Geobacter and Magnetospirillum , fix atmospheric dinitrogen. 相似文献
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Sandeep Shankar C. Douglas Hershberger & A. M. Chakrabarty 《Molecular microbiology》1997,24(3):477-487
We report the purification and characterization of the enzyme nucleoside diphosphate kinase (Ndk) from Mycobacterium smegmatis . The N-terminus of the enzyme was blocked but an internal sequence showed approx. 70% homology with the same enzymes from Pseudomonas aeruginosa and Escherichia coli . Immobilization of the mycobacterial nucleoside diphosphate kinase on a Sepharose 4B matrix and passing the total cell extract through it revealed four proteins (P70 , P65 , P60 , and P50 , respectively) of M r 70 kDa, 65 kDa, 60 kDa and 50 kDa that were retained by the column. While the proteins of M r 70 kDa and 50 kDa modulated the activity of Ndk directing it towards GTP synthesis, the 60 kDa protein channelled the specificity of Ndk entirely towards CTP synthesis. The 65 kDa protein modulated the specificity of Ndk directing it entirely towards UTP synthesis. The specificity for such mycobacterial proteins towards NTP synthesis is retained when they are complexed with P. aeruginosa Ndk. We further demonstrate that the P70 protein is pyruvate kinase and that each of the four proteins forms a complex with Ndk and alters its substrate specificity. Given the ubiquitous nature of Ndk in the living cell and its role in maintaining correct ratios of intracellular nucleoside triphosphates, the implications of the occurrence of these complexes have been discussed in relation to the precursor pool for cell wall biosynthesis as well as RNA/DNA synthesis. 相似文献
20.
Ki-Seok Yoon Yukiko Sakai Natsuki Tsukada Kiyoshi Fujisawa & Hirofumi Nishihara 《FEMS microbiology letters》2009,290(1):114-120
Membrane-bound [NiFe]-hydrogenase from Hydrogenophaga sp. AH-24 was purified to homogeneity. The molecular weight was estimated as 100±10 kDa, consisting of two different subunits (62 and 37 kDa). The optimal pH values for H2 oxidation and evolution were 8.0 and 4.0, respectively, and the activity ratio (H2 oxidation/H2 evolution) was 1.61 × 102 at pH 7.0. The optimal temperature was 75 °C. The enzyme was quite stable under air atmosphere (the half-life of activity was c . 48 h at 4 °C), which should be important to function in the aerobic habitat of the strain. The enzyme showed high thermal stability under anaerobic conditions, which retained full activity for over 5 h at 50 °C. The activity increased up to 2.5-fold during incubation at 50 °C under H2 . Using methylene blue as an electron acceptor, the kinetic constants of the purified membrane-bound homogenase (MBH) were V max =336 U mg−1 , k cat =560 s−1 , and k cat / K m =2.24 × 107 M−1 s−1 . The MBH exhibited prominent electron paramagnetic resonance signals originating from [3Fe–4S]+ and [4Fe–4S]+ clusters. On the other hand, signals originating from Ni of the active center were very weak, as observed in other oxygen-stable hydrogenases from aerobic H2 -oxidizing bacteria. This is the first report of catalytic and biochemical characterization of the respiratory MBH from Hydrogenophaga . 相似文献