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PubMed1976

Sulphydryl groups in photosynthetic energy conservation. I. Light-dependent inhibition of photophosphorylation by the sulphydryl reagent 2-2'dithio bis-(5-nitropyridine).

1. The sulphydryl reagent 2-2'dithio bis-(5-nitropyridine) (DTNP) inhibited photophosphorylation when the chloroplasts were preincubated with the reagent in the light. A maximum inhibition of about 50% was obtained in the presence of pyocyanine and MgCl 2 at 0.3 mumol DTNP per mg chlorophyll and was completed in about 40 s of preillumination. 2. Dithioerythritol, ADP plus Pi (or arsenate) and uncouplers prevented the inhibition when present during the preillumination while phloridzin, Dio-9 and discarine B were ineffective. Low concentrations of ADP or ATP afforded partial protection but other nucleotides had no effect. 3. DTNP inhibited the coupled electron transport rate to the basal level and had no effect on the uncoupled electron transport. The stimulation of proton uptake and inhibition of electron transport by ATP was prevented by DTNP. 4. The trypsin-activated but not the light- and dithioerythritol-triggered ATPase was inhibited by light preincubation of chloroplasts with DTNP. 5. Reversal of DTNP inhibition of photophosphorylation was obtained by a second preillumination in the presence of thiol groups. 6. More DTNP reacted with chloroplasts in the light than in the dark. Two mol of thione were formed in the light per mol of DTNP disappeared. 7. The results suggested that DTNP inhibition is related to the oxidation by DTNP of chloroplast vicinal dithiols probably exposed by a light-induced conformational change.

Adenosine Triphosphate↗
PubMed1979

Light dependence of the decay of the proton gradient in broken chloroplasts.

The initial rates and steady-state values of proton uptake by broken chloroplasts have been measured as functions of light intensity at various concentrations of chlorophyll, pyocyanine, supporting electrolyte, buffer, as well as pH and temperature. Kinetics analysis of the data shows that the rate of decay of proton gradient due to backward leakage depends on light intensity. Under steady illumination, the decay constant kL is equal to kD + mR0, where R0 is the initial rate of proton uptake which is a function of light intensity, kD is the decay constant in the dark and m is a parameter which is independent of light intensity. Treatment of chloroplasts with lysolecithin, neutral detergent, 2,4-dinitrophenol, or valinomycin in the presence of K+ increases kD without affecting m. Treatment with N,N'-dicyclohexylcarbodiimide or adenylyl imidodiphosphate under appropriate conditions decreases m without affectsity and hence m = 0. These results suggest that the light-dependent part (mR0) of kL is due to leakage of protons through the coupling factor (CF1-CF0) complex which can open or close depending on light intensity and that the light independent part (kD) of the decay constant kL is due to proton leakage elsewhere.

Adenylyl Imidodiphosphate↗
PubMed1992

Nitric oxide synthase in macula densa regulates glomerular capillary pressure.

Tubular-fluid reabsorption by specialized cells of the nephron at the junction of the ascending limb of the loop of Henle and the distal convoluted tubule, termed the macula densa, releases compounds causing vasoconstriction of the adjacent afferent arteriole. Activation of this tubuloglomerular feedback response reduces glomerular capillary pressure of the nephron and, hence, the glomerular filtration rate. The tubuloglomerular feedback response functions in a negative-feedback mode to relate glomerular capillary pressure to tubular-fluid delivery and reabsorption. This system has been implicated in renal autoregulation, renin release, and longterm body fluid and blood-pressure homeostasis. Here we report that arginine-derived nitric oxide, generated in the macula densa, is an additional intercellular signaling molecule that is released during tubular-fluid reabsorption and counters the vasoconstriction of the afferent arteriole. Antibody to rat cerebellar constitutive nitric oxide synthase stained rat macula densa cells specifically. Microperfusion of the macula densa segment of single nephrons with N omega-methyl-L-arginine (an inhibitor of nitric oxide synthase) or with pyocyanin (a lipid-soluble inhibitor of endothelium-derived relaxation factor) showed that generation of nitric oxide can vasodilate the afferent arteriole and increase glomerular capillary pressure; this effect was blocked by drugs that prevent tubular-fluid reabsorption. We conclude that nitric oxide synthase in macula densa cells is activated by tubular-fluid reabsorption and mediates a vasodilating component to the tubuloglomerular feedback response. These findings imply a role for arginine-derived nitric oxide in body fluid-volume and blood-pressure homeostasis, in addition to its established roles in modulation of vascular tone by the endothelium and in neurotransmission.

Amino Acid Oxidoreductases↗
PubMed1979

Differentiation of fluorescent pseudomonads by their effect on milk agar.

Eighty-six clinical isolates of fluorescent pseudomonads that did not produce pyocyanin on Diagnostic Sensitivity Test Agar or Cetrimide Agar were identified on the basis of their antibiotic sensitivity, production of pigment on King's "A" medium, growth at 42 degrees C, production of lecithinase and hydrolysis of gelatin. The identity of the strains was confirmed in tests with the ammonium salt sugars ethanol, glucose and mannitol. These tests were adequate for distinguishing between the three important fluorescent pseudomonads. The detection of casein hydrolysis on milk agar was assessed as a rapid method of distinguishing P. aeruginosa from the other species of fluorescent pseudomonads but proved unhelpful when compared with, or included in, a small set of tests. Most strains of P. aeruginosa and P. fluorescens hydrolysed casein.

Agar↗
PubMed1975

Inhibition of Cryptococcus neoformans by Pseudomonas aeruginosa.

Pseudomonas aeruginosa was found to produce a factor or factors that inhibited Cryptococcus neoformans and appeared to be extracellular because the anti-C. neoformans activity was readily demonstrable in medium after the removal and killing of Pseudomonas organisms. Production of the inhibitor material was greatest in DST Agar after prolonged incubation and was reduced in the presence of glucose. A part of the inhibitory material was found to be chromatographically distinct from pyocyanin.

Antibiosis↗
PubMed2025

Pseudomonas aeruginosa phenazines dictate site-specific competitive interactions with Klebsiella pneumoniae.

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.

Journal Article↗
PubMed2025

Mapping genetic and phenotypic diversity of Pseudomonas aeruginosa across clinical and environmental isolation sites.

Pseudomonas aeruginosa is a clinically significant opportunistic pathogen adept at thriving in both host-associated and environmental settings. To define the extent to which P. aeruginosa isolates specialize across niches and identify genotype-phenotype correlates, we performed whole genome sequencing and comprehensive phenotypic characterization of 125 P. aeruginosa isolates from diverse clinical and environmental sites, evaluating virulence-associated traits, including motility, cytotoxicity, biofilm formation, pyocyanin production, and antimicrobial susceptibility. We identify that genomic diversity does not correlate with isolation source or most virulence phenotypes. Instead, we find that the two major P. aeruginosa clades (Groups A and B) delineate phylogeny and cytotoxicity, with Group B strains showing significantly higher cytotoxicity than Group A. Sequence analysis revealed previously uncharacterized alleles of genes encoding type III secretion effector proteins. We observed high variability amongst strains and isolation sources in all four assayed virulence phenotypes. Antimicrobial resistance (AMR) is exclusively observed in clinical isolates, not environmental, reflecting antibiotic exposure-driven selection. Bacterial GWAS revealed a statistically significant association between cytotoxicity and exoU presence, and we identified a novel exoU allelic variant with decreased cytotoxicity, demonstrating that functional diversity within well-characterized virulence factors may still influence pathogenic outcomes. In summary, our analyses of 125 diverse isolates suggest that the ability of P. aeruginosa to thrive across diverse niches is driven by broadly conserved genetic repertoire rather than niche-specific accessory genes.

Journal Article↗
PubMed1979

Oxidation of carbon monoxide in cell extracts of Pseudomonas carboxydovorans.

Extracts of aerobically, CO-autotrophically grown cells of Pseudomonas carboxydovorans were shown to catalyze the oxidation of CO to CO(2) in the presence of methylene blue, pyocyanine, thionine, phenazine methosulfate, or toluylene blue under strictly anaerobic conditions. Viologen dyes and NAD(P)(+) were ineffective as electron acceptors. The same extracts catalyzed the oxidation of formate and of hydrogen gas; the spectrum of electron acceptors was identical for the three substrates, CO, formate, and H(2). The CO- and the formate-oxidizing activities were found to be soluble enzymes, whereas hydrogenase was membrane bound exclusively. The rates of oxidation of CO, formate, and H(2) were measured spectrophotometrically following the reduction of methylene blue. The rate of carbon monoxide oxidation followed simple Michaelis-Menten kinetics; the apparent K(m) for CO was 45 muM. The reaction rate was maximal at pH 7.0, and the temperature dependence followed the Arrhenius equation with an activation energy (DeltaH(0)) of 35.9 kJ/mol (8.6 kcal/mol). Neither free formate nor hydrogen gas is an intermediate of the CO oxidation reaction. This conclusion is based on the differential sensitivity of the activities of formate dehydrogenase, hydrogenase, and CO dehydrogenase to heat, hypophosphite, chlorate, cyanide, azide, and fluoride as well as on the failure to trap free formate or hydrogen gas in coupled optical assays. These results support the following equation for CO oxidation in P. carboxydovorans: CO + H(2)O --> CO(2) + 2 H(+) + 2e(-) The CO-oxidizing activity of P. carboxydovorans differed from that of Clostridium pasteurianum by not reducing viologen dyes and by a pH optimum curve that did not show an inflection point.

Aldehyde Oxidoreductases↗
PubMed1977

Mannose-binding hemagglutinins in extracts of Pseudomonas aeruginosa.

Mannose-binding hemagglutinins were found in the extracts of a pyocyanin-forming Pseudomonas aeruginosa, which contain galactose-specific hemagglutinins. They were purified simultaneously with the latter proteins by heating to 70 degrees C, precipitating with ammonium sulfate, application to a Sepharose 4B column, and elution from it by 0.05 M mannose. The mannose-specific hemagglutinins were shown to be similar to the galactophilic ones in (a) being glycoproteins of very low molecular weight (about 11 000 by SDS gel electrophoresis), (b) their tendency to aggregate, and (c) their ability to effect stronger agglutination of erythrocytes treated with papain than of untreated ones. They were found to resemble them also in their reaction with simple sugars and interactions with divalent cations, which are essential for their activity. In these properties, as well as in their relative resistance to heat and to proteolytic enzymes, these two types of bacterial hemagglutinins are like most of the plant, contrasted with the animal, hemagglutinins. The reactions with mannose and mannose-bearing compounds (yeast mannan, horseradish peroxidase (EC 1.11.1.7), and serum globulins), which are not shared with the galactophilic Pseudomonas hemagglutinins, indicate a relationship of the mannose-binding protein of Pseudomonas to the plant lectin concanavalin A. The mannose-binding hemagglutinins do not exhibit identical cell-agglutinating spectra owing to difference in profiles of sugar specificity and relative affinity to mannose derivatives compared with free mannose.

Agglutinins↗
PubMed1975

[In vitro examination on antibacterial activities of broad-spectrum antibiotics against gram-negative clinical isolates (author's transl)].

In vitro studies were undertaken on clinically isolated strains of various bacteria to examine the antibacterial activity of ampicillin (AB-PC), carbenicillin (CB-PC), sulbenicillin (SB-PC) cephalothin (CET), cefazolin (CEZ) and gentamicin (GM). Fifty three % of Escherichia coli strains 53.3% of Citrobacter sp., 80% of Proteus mirabilis, 42.9% of Morganella and 80% of Bacteroides sp. were susceptible (MIC being not higher than 12.5 mug/ml) to AB-PC. The eight other species were not so susceptible to this penicillin. CB-PC and SB-PC were almost as effective as AB-PC against Escherichia coli and Citrobacter sp. They were less active against Klebsiella sp., but more active against Enterobacter sp., Serratia sp., indole-positive Proteus group and Pseudomonas sp. than AB-PC, SB-PC was more effective than CB-PC against Pseudomonas sp. The strains of Pseudomonas sp. which were resistant to higher concentrations of CB-PC and SB-PC were pyocyanine-negative strains. All strains (100%) of Escherichia coli, Klebsiella sp. and Citrobacter sp. were susceptible to CET and CEZ, while none of Enterobacter sp. , Serratia sp., Proteus vulgaris. Morganella, Rettgerella, Providencia and Pseudomonas sp. were susceptible to these cephalosporins. The MICs of CET and CEZ against Bacteroides sp. were moderately low. Some strains of Providencia and Alkaligenes sp. were resistant of GM but the other 10 species were not resistant to this antibiotic, though it showed comparatively high MICs against Bacteroides sp. When seen from the MIC distribution of each antibiotic, there was a tendency that the strains isolated from the pus were more resistant than those isolated from the other sources (urine, sputum and bile).

Ampicillin↗
PubMed1977

[Virulence of human and environmental strains of "pseudomonas aeruginosa" in mice (author's transl)].

The virulence of 21 clinical isolates and 10 environmental strains of Pseudomonas aeruginosa was studied by intraperitoneal challenge in mice. The LD50 values of human strains ranged from 10(7),(0) to 10(8),(5) viable cells per mouse (average: 10(7),(7)(2)). The LD50 of environmental strains ranged from 10(7),(2) to 10(8),(1) (average: 10(7),(59)). These results are not significantly different. Experimental virulence for mice of P. aeruginosa strains found in hospital environment allows no prediction on their level of pathogenicity for in-patients. Furthermore, this study proved no relationship between letal effect of P. aeruginosa for mice and following characters of strains: O serogroup, untypability and productivity of specific pigments, pyocyanin and pyorubrin.

Animals↗
PubMedDate not supplied

[Pseudomonas aeruginosa III. Identification of strains isolated from blue foxes (Alopex lagopus) in a Danish fur farm (author's transl)].

The technique of determining bacterial strains as Ps. aeruginosa is described. It was attempted to base this technique upon well-defined commercial preparations, so as to afford a possibility for comparative studies. 261 strains presumed to be Ps. aeruginosa were isolated from sick and healthy blue foxes and their watering troughs. 244 of the strains could be subjected to detailed bacteriological study (Table I a, b, c, fig. 1) in addition to the demonstration of pigment (pyocyanin and fluorescin). All 244 proved to be Ps. aeruginosa. Among them 10 non-pigment-producing strains were characterized as "atypical" Ps. aeruginosa strains. The determination of the genus was supported by the results of the sensitivity tests (Table II).

Animals↗
PubMed1977

Similar C-phycocyanins from two strains of thermotolerant cyanophyte Mastigocladus laminousus.

C-phycocyanin from two strains of the thermotolerant blue-green alga, Mastigocladus laminosus (NZ-DB2-m and I-30-m), that grow within different temperature ranges have been characterized with respect to aggregation, immunologic properties, subunit composition, and thermodenaturation. The critical thermal-denaturation temperature for phycocyanin from both strains of M. laminosus phycocyanin is 60 degrees C which is higher than that for mesophilic phyococyanin. Immunodiffusion studied have shown that these two strains of M. laminosus exhibit no antigenic differences and are closely related to the mesophilic Plectonema calothricoides and the thermophilic Synechococcus lividus (strains 3). Neither phenol nor alpha-naphthol has any effect on phycocyanin aggregation in these two strains of M. laminosus. There is also no enhancement of formation of large aggregates at their elevated temperature of cultivation. Furthermore, the phycocyanin of both strains of M. laminosus does not demonstrate any large amount of 19S or higher aggregates at any pH value. These observations suggest that the mode of adaptation of M. laminosus phycocyanin to high temperature is differnet from the previously encountered. It is also important to note that phycocyanin is essentially unchanged whether it is extracted from the same strain, M. laminosus (NZ-DBS-m), grown at either 50 degrees C or 37 degrees C.

Adaptation, Biological↗