Conjugative plasmid coding for the metabolism of 2-chlorobenzoic acid byPseudomonas aeruginosa

Summary A 2-chlorobenzoic acid (2-CBA) utilizing strain ofPseudomonas aeruginosa (B₁₆) has been isolated from soil by enrichment with 2-CBA. The trait for utilization of 2-CBA as sole source of carbon and energy was lost spontaneously and by treatment with growth-limiting concentration of mitomycin C. Genes coding for 2-CBA catabolism are transferrable to 2-CBA^– variants through conjugation.

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Code plasmidique conjugué du métabolisme de l'acide 2-chlorobenzoïque

Résumé Une souche dePseudomonas aeruginosa (B₁₆) utilisant l'acide 2-chlorobenzoïque (2-CBA) a été isolée du sol par enrichissement sur le 2-CBA. L'aptitude à utiliser le 2-CBA comme seule source de carbone et d'énergie a été perdue spontanément et par traitement avec une concentration limitant la croissance de mitomycine-C. Les gènes codant pour le catabolisme du 2-CBA sont transférables aux variants 2-CBA^– par conjugaison.

     

Hemolytic effect of a glycolipid produced byPseudomonas aeruginosa

Summary The toxicity of the glycolipid ofPs. aeruginosa to mice has to be ascribed to the fact that it causes hemolysis by dissolving materials from the cell wall structure of the red blood cells.     

Enzymes involved in the biosynthesis of alginate byPseudomonas aeruginosa

Summary Analysis of the enzymes involved in the biosynthesis of alginic acid by mucoidPseudomonas aeruginosa PAO strain's determined the presence of enzymes required to synthesise GDP-mannuronic acid. Addition of polymannuronic acid to an ammonium sulphate precipitate of a cell free alginate suspension indicated the presence of an enzyme which catalysed the epimerisation of mannuronic acid to guluronic acidafter the polymer had been synthesised. The epimerase was shown to be calcium dependant.Various non-mucoid mutants were also studied. The non-mucoid parental strain PAO 381 also contained the enzymes required for alginate synthesis but they were not expressed. Synthesis of alginic acid led to an increase in the level of these enzymes. In the non-mucoid mutants derived from mucoid parents GDP-mannose dehydrogenase was absent in all strains studied. In some of these strains GDP-mannose pyrophosphorylase was also absent, while in other strains, phosphomannase isomerase was absent or greatly reduced.     

Influence of aeration on hydrogen cyanide biosynthesis byPseudomonas aeruginosa

Batch cultures ofPseudomonas aeruginosa were able to produce only low levels of cyanide during logarithmic growth with adequate aeration. The reduction of aeration caused a rapid increase in the ability of such cultures to produce hydrogen cyanide. The immediacy and the magnitude of this response depended on the oxygen level, with a concentration of 4% in the aeration gas giving optimal results. The reestablishment of normal aeration resulted in a cessation of the increase of the culture's cyanogenic capacity. This effect appeared to be a combination of inactivation of the hydrogen cyanide synthase and repression of synthesis of this enzyme.     

Products of the oxidation ofn-decane byPseudomonas aeruginosa andMycobacterium rhodochrous

Pseudomonas aeruginosa andMycobacterium rhodochrous (both soil isolates) have been grown in a mineral salts medium containing hydrocarbon as the only carbon source. The fermentation products from decane withPseudomonas aeruginosa were 1-, 2-, 3-, and 4- and or 5-decanol and the corresponding ketones (no decanal was found) and decanoic, nonanoic, octanoic and heptanoic acid. This indicates that non-specific first oxidation occurs followed by seission of the decanone at the keto group. The products fromMycobacterium rhodochrous were 1-decanol,n-decanal, decanoic, octanoic, hexanoic, butyric and acetic acids, indicating that initial terminal oxidation is followed by-oxidation.     

2-Deoxy-d-lyxo-hexonic Acid from 2-Deoxy-d-lyxo-hexose byPseudomonas aeruginosa Fermentation

Aerobic fermentation of media or solutions containing 2-deoxy-D-lyxo-hexose and calcium carbonate by bacterial cells capable of oxidizing aldoses to aldonic acids was used to prepare 2-deoxy-D-lyxo-hexonic acid; the acid was isolated in a 62% yield in the form of its 1,4-lactone.     

Isolation and identification of antialgal substances produced byPseudomonas aeruginosa

Pseudomonas aeruginosa strongly inhibited the growth of green microalgae and cyanobacteria by the release of low molecular weight, thermoresistant factors. The antialgal substances were resistant to various enzymes and remained active in agar after a 3-months storage period at 4 °C in the absence of light. The results indicate that inhibition of algal growth was mediated by the phenazine pigments released by the bacterium. Pyocyanine and an unidentified pale blue pigment had no effect on algal growth, whereas 1-hydroxyphenazine and oxychlororaphine showed strong antialgal activity.Groupe de Recherche en Recyclage Biologique et AquicultureDépartement des Sciences et Technologie des Aliments     

Monitoring of denitrification byPseudomonas aeruginosa using on-line fluorescence technique

Summary The NAD(P)H fluorescence ofPseudomonas aeruginosa dropped sharply upon addition of nitrate to an anaerobic culture, indicating that denitrification is not limited by mass transfer of nitrate through cell membrane to reach nitrate reductase. The effect of added nitrate concentration on fluorescence drop followed a typical saturation kinetics. The maximum specific denitrification rate under the studied condition was found to be 0.26±0.05 g NO ₃ ⁻ -N/g cells-hr.     

Production of extracellular emulsifying agent byPseudomonas aeruginosa UG1

Summary Twenty-three bacterial strains were isolated from oil-contaminated soil samples. Of these, 20 displayed some ability to effect oil dispersion and they were screened quantitatively for the ability to emulsify 0.5% (v/v) reference oil. One strain, identified asPseudomonas aeruginosa UG1, produced extracellular material that emulsified reference oil, hexadecane and 2-methylnaphthalene at concentrations as high as 6% (v/v) in nutrient broth. Emulsification activity increased during a 10 day incubation period at 30°C. The activity was not influenced by pH over the range 5 to 9. The emulsifying agent was precipitated by cold ethanol. The highest emulsifying activity was detected in the extracellular fraction precipitated between 30 and 50% (v/v) ethanol. A linear relationship was observed between emulsifier concentration (mg/ml) and emulsifying activity. Genetic analysis showed that thePseudomonas aeruginosa UG1 strain did not carry extrachromosomal plasmids, suggesting that the gene(s) coding for emulsifying activity was carried on the chromosome.     

Disturbance of lymphocyte circulation byPseudomonas aeruginosa infection in oxazolone-sensitized mice

Pseudomonas aeruginosa infection depresses contact sensitivity to oxazolone in mice. To test whether an altered lymphocyte circulation plays a role in this depression⁵¹Cr-labeled lymphocytes fromP. aeruginosa-infected and oxazolone-sensitized donors were injected intravenously into infected and sensitized recipients, and the radioactivity uptake of several organs was determine. The controls consisted of normal mice receiving labeled lymphocytes from normal donors. While the radioactivity recovered from the liver, spleen, and mesenteric lymph nodes was similar in the test and the control group, significantly more radioactivity was recovered from the draining lymph nodes of infected and sensitized recipients. The concentration of labeled lymphocytes from sensitized donors in the draining lymph nodes of sensitized recipients was 18% greater than that of the controls but 31% lower than that of infected and sensitized animals receiving cells from infected and sensitized donors.P. aeruginosa infection enhances lymphocyte entrapment within the draining lymph nodes of oxazolone-sensitized mice.     

Kinetic studies on surfactant production byPseudomonas aeruginosa 44T1

Summary Biosurfactant accumulation occurred in the exponential and stationary phases. Production started when the nitrogen level was very low. Surfactant was produced with a diauxic pattern. Rhamnolipid concentration increased as nitrogen levels increased. Maximum product yield (Y _p/x) 2.9 was detected when C/N ratio was 6.6 and specific rate of product formation (p _q) was calculated. The examination of these kinetics parameters such as product yield and specific rate of product formation should be taken into account to develop a high efficient production process.     

Optimisation of rhamnolipids produced byPseudomonas aeruginosa 181 using Response Surface Modeling

This work investigated the optimisation of the fermented culture medium for maximisation of rhamnolipids production produced byPseudomonas aeruginosa 181 using Response Surface Modeling (RSM). A two full factorial central composite experimental design was used in the design of experiments and in the analysis of results. This procedure limited the number of actual experiments performed while allowing for possible interactions between the parameters (pH, stirring rate, casamino acid concentration and incubation period) on the production of biosurfactants. Production carried out at larger volumes of one litre using Bioreactor under RSM-optimised conditions yielded 3.61 g l^?1 of products after purification by acid precipitation.     

Optimization of lipase production byPseudomonas aeruginosa MB 5001 in batch cultivation

Summary The production ofPseudomonas aeruginosa MB 5001 extracellular lipase was optimized by batch cultivation employing shake flasks and 23-L bioreactors. This enzyme efficiently and selectively bioconverts dimethyl 5-(3-(2-(7-chloroquinolin-2-yl)ethyl)phenyl)4,6-dithianonanedioate (diester) to its (S)-ester acid. Process development studies focused on the identification and optimization of the physicochemical parameters required to achieve maximum lipase production. Of the media evaluated, a peptonized milk-based medium was found to support excellent lipase production and stability. Medium composition and process parameters that supported optimal lipase production were different from those supporting maximum biomass formation. Of the parameters investigated, dissolved oxygen tension had the most significant and unexpected impact on lipase production. Elevated lipase production was achieved whenP. aeruginosa MB 5001 was cultivated in a dissolved oxygen limited environment. Overall, these process development studies resulted in a 100% increase in lipase production when compared to the original shake flask process employing skim milk.     

Threonine metabolism in Japanese quail liver

Summary. In general, threonine is metabolized by reaction catalyzed by threonine-3-dehydrogenase (TDH), threonine dehydratase (TH) or threonine aldolase (TA). The activities of these three enzymes were compared in the liver of Japanese quails and rats. The animals were fed a standard or threonine rich-diet, or fasted for 3 days. The specific activity of TDH in the liver from quail fed a standard diet was 11 times higher than that in the liver from rats fed a standard diet. The TDH activities in the livers of the fasting and 5% threonine-rich diet groups of quail were 3 and 2 times higher than those in the livers from quail fed the standard diet, respectively. The TH activity in the liver of rats fed a standard diet was 14 times higher than that in the liver of quail fed a standard diet. The TH activity in the rat liver after fasting was 2.3 times higher than that of the standard diet control. The activity of TA in the livers of rat and quail were so low that its role in threonine metabolism in both animals seemed to be negligible. These results suggest that threonine is a ketogenic amino acid in the quail liver, while it is a glucogenic in the rat liver.     

Threonine phosphorylation post-translationally regulates protein secretion in Pseudomonas aeruginosa

Secreted proteins are crucial to the arsenal of bacterial pathogens. Although optimal activity of these proteins is likely to require precise regulation of release, the signalling events that trigger secretion are poorly understood. Here, we identify a threonine phosphorylation event that post-translationally regulates the Hcp secretion island-I-encoded type VI secretion system of Pseudomonas aeruginosa (H-T6SS). We show that a serine-threonine kinase, PpkA, is required for assembly of the H-T6SS and for secretion of Hcp1. PpkA activity is antagonized by PppA, a Ser-Thr phosphatase. These proteins exhibit reciprocal effects on the H-T6SS by acting on an FHA domain-containing protein, termed Fha1. Colocalization experiments with the T6S AAA+ family protein, ClpV1, indicate that Fha1 is a core scaffolding protein of the H-T6SS. Mutations affecting this H-T6S regulatory pathway provide a molecular explanation for the variation in Hcp1 secretion among clinical P. aeruginosa isolates. This mechanism of triggering secretion may be general, as many T6SSs contain orthologues of these proteins. Post-translational regulation of protein secretion by Thr phosphorylation is unprecedented in bacteria, and is likely to reflect the requirement for T6S to respond rapidly and reversibly to its environment.     

Effect of carbon and nitrogen sources on neutral proteinase production byPseudomonas aeruginosa

A strain ofPseudomonas aeruginosa from soil produced large quantitaties of extracellular neutral proteinase and could utilize several organic substances as carbon and nitrogen sources for enzyme production. The growth media required the presence of a high amount of phosphate when glucose was the carbon source. The intermediates of citric-acid cycle acids supported the proteinase production more than any other carbon sources. However, complex nitrogenous substances supported enzyme production more efficiently. Higher concentration of casamino acids suppressed the proteinase synthesis.     

Iridescent material and the effect of iron on its production byPseudomonas aeruginosa

The nutritional conditions controlling iridescence inPseudomonas aeruginosa were studied using synthetic media solidified with agar. Iron and magnesium were growth-limiting factors in media solidified with dialysed agar. Iridescence only occurred on iron-deficient media and was not suppressed by adding Ca, Cu, Mn and Zn to these media. The ultraviolet absorption spectrum of the iridescent material was almost identical to the spectrum of the pyo I substances which are 2-alkyl-4-quinolinols.The amount of material produced was inversely proportional to the iron content of the medium. Small amounts of material were produced by cells grown at levels of iron optimal for growth. Synthesis of 2-alkyl-4-quinolinol may be a normal metabolic process in the iridescent strains ofPseudomonas aeruginosa. It was enhanced by anthranilic acid and tryptophan; kynurenine and kynurenic acid had no effect. The results can be explained if it is assumed that the activity of iron-requiring enzymes catalizing the breakdown of tryptophan is reduced.Even in the presence of anthranilic acid or tryptophan no material was produced by a non-iridescent strain.     

The effects of 2,4-dinitrophenol on the oxidation of fatty acids byPseudomonas aeruginosa

Summary The effects of varying concentrations of 2,4-dinitrophenol on the oxidation of a series of saturated, aliphatic fatty acids byPs. aeruginosa were studied. The oxidation of C₄, C₆, C₈, C₁₀, C₁₂, C₁₃, C₁₄ and C₁₆ acids is stimulated by certain concentrations of this inhibitor. However, the concentration of 2,4-dinitrophenol which causes stimulation of oxygen uptake with capric acid does not produce an increase in numbers of the organisms in a medium containing the fatty acid as the sole carbon source. This investigation was supported by a Fellowship from the Anderson Oil and Chemical Company, Inc., Portland, Connecticut.