Characterization of Pseudomonas spp. associated with spoilage of gilt-head sea bream stored under various conditions.

The population dynamics of pseudomonads in gilt-head sea bream Mediterranean fish (Sparus aurata) stored under different conditions were studied. Phenotypic analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins were performed to identify a total of 106 Pseudomonas strains isolated from S. aurata stored under different temperatures (at 0, 10, and 20 degrees C) and packaging conditions (air and a modified atmosphere of 40% CO(2)-30% N(2)-30% O(2)). Pseudomonas lundensis was the predominant species, followed by Pseudomonas fluorescens, while Pseudomonas fragi and Pseudomonas putida were detected less frequently. Fluorescent Pseudomonas strains dominated under air conditions, while proteolytic and less lipolytic strains dominated under modified-atmosphere packaging. Different storage conditions appear to govern the selection of pseudomonads in gilt-head sea bream fish.     

Anaerobic oxidation of 2-chloroethanol under denitrifying conditions by<Emphasis Type="Italic"> Pseudomonas stutzeri</Emphasis> strain JJ

A bacterium that uses 2-chloroethanol as sole energy and carbon source coupled to denitrification was isolated from 1,2-dichloroethane-contaminated soil. Its 16 S rDNA sequence showed 98% similarity with the type strain of Pseudomonas stutzeri (DSM 5190) and the isolate was tentatively identified as Pseudomonas stutzeri strain JJ. Strain JJ oxidized 2-chloroethanol completely to CO(2) with NO(3)(- )or O(2) as electron acceptor, with a preference for O(2) if supplied in combination. Optimum growth on 2-chloroethanol with nitrate occurred at 30 degrees C with a mu(max) of 0.14 h(-1) and a yield of 4.4 g protein per mol 2-chloroethanol metabolized. Under aerobic conditions, the mu(max) was 0.31 h(-1). NO(2)(-) also served as electron acceptor, but reduction of Fe(OH)(3), MnO(2), SO(4)(2-), fumarate or ClO(3)(-) was not observed. Another chlorinated compound used as sole energy and carbon source under aerobic and denitrifying conditions was chloroacetate. Various different bacterial strains, including some closely related Pseudomonas stutzeri strains, were tested for their ability to grow on 2-chloroethanol as sole energy and carbon source under aerobic and denitrifying conditions, respectively. Only three strains, Pseudomonas stutzeri strain LMD 76.42, Pseudomonas putida US2 and Xanthobacter autotrophicus GJ10, grew aerobically on 2-chloroethanol. This is the first report of oxidation of 2-chloroethanol under denitrifying conditions by a pure bacterial culture.     

Response to lethal UVA radiation in the Antarctic bacterium Pseudomonas extremaustralis: polyhydroxybutyrate and cold adaptation as protective factors

Extremophiles - Pseudomonas extremaustralis is an Antarctic bacterium with high stress resistance, able to grow under cold conditions. It is capable to produce polyhydroxyalkanoates (PHAs) mainly...     

Characterization of Pseudomonas spp. Associated with Spoilage of Gilt-Head Sea Bream Stored under Various Conditions

The population dynamics of pseudomonads in gilt-head sea bream Mediterranean fish (Sparus aurata) stored under different conditions were studied. Phenotypic analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins were performed to identify a total of 106 Pseudomonas strains isolated from S. aurata stored under different temperatures (at 0, 10, and 20°C) and packaging conditions (air and a modified atmosphere of 40% CO₂-30% N₂-30% O₂). Pseudomonas lundensis was the predominant species, followed by Pseudomonas fluorescens, while Pseudomonas fragi and Pseudomonas putida were detected less frequently. Fluorescent Pseudomonas strains dominated under air conditions, while proteolytic and less lipolytic strains dominated under modified-atmosphere packaging. Different storage conditions appear to govern the selection of pseudomonads in gilt-head sea bream fish.     

A cytochrome b-like pigment with a peak at 567 nm in Pseudomonas aeruginosa.

A cytochrome b - like pigment with an absorption peak at 567 nm was detected in Pseudomonas aeruginosa irrespective of whether the organism was grown aerobically or anaerobically under denitrifying conditions. This pigment has not been reported previously for P. aeruginosa but it has been detected in other denitrifying bacteria including closely related Pseudomonas species.     

Biochemistry of nitrate respiration in Pseudomonas stutzeri. I. Aerobic and nitrate respiration routes of carbohydrate catabolism

Spangler, W. J. (Oregon State University, Corvallis), and C. M. Gilmour. Biochemistry of nitrate respiration in Pseudomonas stutzeri. I. Aerobic and nitrate respiration routes of carbohydrate catabolism. J. Bacteriol. 91:245-250. 1966.-The metabolic pathways of glucose catabolism were studied in Pseudomonas stutzeri under aerobic conditions and under conditions of nitrate respiration. Studies on both glucose and gluconate catabolism, by the radiorespirometric method, indicated that these substrates are degraded in the same manner, i.e., the Entner-Doudoroff and pentose phosphate pathways. There appeared to be no major shift in primary metabolic pathways when nitrate was used as the terminal hydrogen acceptor in nitrate respiration as opposed to aerobic respiration with free molecular oxygen. It was shown that glucose is not degraded to any appreciable extent under anaerobic conditions in the absence of nitrate. Tentative evidence suggests that the tricarboxylic acid cycle functions under both conditions of oxygen relationships and that the rate of carbon oxidation via the tricarboxylic acid cycle is slower with nitrate respiration than under aerobic conditions.     

Agricultural Plants and Soil as a Reservoir for Pseudomonas aeruginosa

Pseudomonas aeruginosa was detected in 24% of the soil samples but in only 0.13% of the vegetable samples from various agricultural areas of California. The distribution of pyocin types of soil and vegetable isolates was similar to that of clinical strains, and three of the soil isolates were resistant to carbenicillin. Pseudomonas aeruginosa multiplied in lettuce and bean under conditions of high temperature and high relative humidity (27 C and 80-95% relative humidity) but declined when the temperature and humidity were lowered (16 C, 55-75% relative humidity). The results suggest that soil is a reservior for P. aeruginosa and that the bacterium has the capacity to colonize plants during favorable conditions of temperature and moisture.     

Temporary low oxygen conditions for the formation of nitrate reductase and nitrous oxide reductase by denitrifying Pseudomonas sp. G59

Formation of nitrate reductase (NaR) and nitrous oxide reductase (N2OR) by a Pseudomonas sp. G59 did not occur in aerobic or anaerobic conditions, but was observed in a microaerobic incubation in which an anaerobically grown culture was agitated in a sealed vessel initially containing 20 kPa oxygen in the headspace. During the microaerobic incubation, the oxygen concentration in the headspace decreased and dissolved oxygen reached 0.1-0.2 kPa. NaR activity was detected immediately and N2OR activity after 3 h of incubation irrespective of the presence or absence of NO3- or N2O. In the presence of NO3-, NO2- was accumulated as a major product, but N2O was observed in low concentrations only after N2OR appeared. After microaerobic incubation for 3 h, N2OR formation continued even anaerobically in an atmosphere of N2O. In contrast, Escherichia coli formed NaR not only microaerobically but also anaerobically. However, NaR formation by E. coli was inhibited by sodium fluoride under anaerobic, but not under microaerobic conditions. The Pseudomonas culture did not possess fermentative activity. It is suggested that the dependence on microaerobiosis for the formation of these reductases by the Pseudomonas culture was due to an inability to produce energy anaerobically until these anaerobic respiratory enzymes were formed.     

Electron self-exchange in Pseudomonas cytochromes

Electron self-exchange has been measured by an NMR technique for cytochromes c551 from Pseudomonas aeruginosa and Pseudomonas stutzeri. The rate for P. aeruginosa cyt c551 is 1.2 x 10(7) M-1 s-1 at 40 degrees C in 50 mM phosphate at pH 7. For P. stutzeri, under the same conditions, the rate is 4 x 10(7) M-1 s-1. For both cytochromes, the rate was independent of ionic strength up to 0.5 M in added NaC1, the enthalpy of activation was 20 +/- 4 kcal mol-1, and the entropy of activation was 38 +/- 10 cal mol-1 deg-1.     

THE DIFFERENTIATION OF PSEUDOMONAS FROM OTHER GRAM-NEGATIVE BACTERIA ON THE BASIS OF ARGININE METABOLISM

SUMMARY: Of 391 Gram-negative bacteria isolated from chicken meat spoiled at a low temperature and classified by the commonly used methods, 156 were considered to be Pseudomonas and 188 Achromobacter , and 47 others belonged to the coli-aerogenes group or remained unclassified. A test for the production of alkaline conditions in an arginine medium incubated under a vaseline seal gave positive results for 155 of the Pseudomonas isolates, and negative results for 1 Pseudomonas and all the 188 Achromobacter strains. When named strains from culture collections were tested under these conditions, 63 Pseudomonas strains produced alkalinity while two plant pathogenic Pseudomonas species and two non-pigmented strains did not. These last two, which produced no acid from glucose, could not be regarded as typical Pseudomonas. All the Achromobacter strains gave negative results, as did four Alcaligenes , but one species, Alcaligenes bookeri , produced slightly alkaline conditions. One strain of Chromobacterium and three of Vibrio were also positive. These could be distinguished from Pseudomonas by their metabolism of glucose.     

Polyamines of carbon monoxide-utilizing bacteria, Pseudomonas thermocarboxydovorans and Pseudomonas carboxydohydrogena

A slightly thermophilic, CO-utilizing pseudomonad, Pseudomonas thermocarboxydovorans grown under both autotrophic and heterotrophic growth conditions was found to contain 2-hydroxyspermidine and 2-hydroxyputrescine in addition to putrescine, diaminopropane and spermidine. A mesophilic CO — utilzing hydrogen bacterium, Pseudomonas carboxydohydrogena contained putrescine and homospermidine under both autotrophic and heterotrophic growth conditions. Although these two carboxydobacteria are classified to the same genus Pseudomonas , the difference in their polyamine distribution patterns suggests that they may belong to different subclasses of Proteobacteria .     

Effect of surface shear stress on the attachment of Pseudomonas fluorescens to stainless steel under defined flow conditions

The application of the radial-flow growth chamber to the study of the initial stages of bacterial adhesion to surfaces under flowing conditions is reported. The adhesive properties of the bacterium Pseudomonas fluorescens (NCIB 9046) to stainless steel (type AISI 316) were found to be highly dependent on surface shear stress and the time and concentration of cells used in the incubation procedure. Maximum levels of adhesion occurred in zones of lowest surface shear stress, particularly less than 6-8 Nm(-2). Adhesion was still noticeable at shear stresses even up to 130 Nm(-2). Significant detachment of cells from a monolayer attached under static conditions was found to occur at surface shear stresses in excess of 10-12 Nm(-2).     

The nitrite reductase gene of Pseudomonas aeruginosa: Effect of growth conditions on the expression and construction of a mutant by gene disruption

Abstract The expression of nitrite reductase has been tested in a wild-type strain of Pseudomonas aeruginosa (Pao1) as a function of nitrate concentration under anaerobic and aerobic conditions. Very low levels of basal expression are shown under non-denitrifying conditions (i.e. absence of nitrate, in both aerobic and anaerobic conditions); anaerobiosis is not required for high levels of enzyme production in the presence of nitrate. A Pseudomonas aeruginosa strain, mutated in the nitrite reductase gene, has been obtained by gene replacement. This mutant, the first of this species described up to now, is unable to grow under anaerobic conditions in the presence of nitrate. The anaerobic growth can be restored by complementation with the wild-type gene.     

Comparison of denitrification by Pseudomonas stutzeri, Pseudomonas aeruginosa, and Paracoccus denitrificans.

A comparison was made of denitrification by Pseudomonas stutzeri, Pseudomonas aeruginosa, and Paracoccus denitrificans. Although all three organisms reduced nitrate to dinitrogen gas, they did so at different rates and accumulated different kinds and amounts of intermediates. Their rates of anaerobic growth on nitrate varied about 1.5-fold; concomitant gas production varied more than 8-fold. Cell yields from nitrate varied threefold. Rates of gas production by resting cells incubated with nitrate, nitrite, or nitrous oxide varied 2-, 6-, and 15-fold, respectively, among the three species. The composition of the gas produced also varied markedly: Pseudomonas stutzeri produced only dinitrogen; Pseudomonas aeruginosa and Paracoccus denitrificans produced nitrous oxide as well; and under certain conditions Pseudomonas aeruginosa produced even more nitrous oxide than dinitrogen. Pseudomonas stutzeri and Paracoccus denitrificans rapidly reduced nitrate, nitrite, and nitrous oxide and were able to grow anaerobically when any of these nitrogen oxides were present in the medium. Pseudomonas aeruginosa reduced these oxides slowly and was unable to grow anaerobically at the expense of nitrous oxide. Furthermore, nitric and nitrous oxide reduction by Pseudomonas aeruginosa were exceptionally sensitive to inhibition by nitrite. Thus, although it has been well studied physiologically and genetically, Pseudomonas aeruginosa may not be the best species for studying the later steps of the denitrification pathway.     

Comparison of denitrification by Pseudomonas stutzeri, Pseudomonas aeruginosa, and Paracoccus denitrificans

A comparison was made of denitrification by Pseudomonas stutzeri, Pseudomonas aeruginosa, and Paracoccus denitrificans. Although all three organisms reduced nitrate to dinitrogen gas, they did so at different rates and accumulated different kinds and amounts of intermediates. Their rates of anaerobic growth on nitrate varied about 1.5-fold; concomitant gas production varied more than 8-fold. Cell yields from nitrate varied threefold. Rates of gas production by resting cells incubated with nitrate, nitrite, or nitrous oxide varied 2-, 6-, and 15-fold, respectively, among the three species. The composition of the gas produced also varied markedly: Pseudomonas stutzeri produced only dinitrogen; Pseudomonas aeruginosa and Paracoccus denitrificans produced nitrous oxide as well; and under certain conditions Pseudomonas aeruginosa produced even more nitrous oxide than dinitrogen. Pseudomonas stutzeri and Paracoccus denitrificans rapidly reduced nitrate, nitrite, and nitrous oxide and were able to grow anaerobically when any of these nitrogen oxides were present in the medium. Pseudomonas aeruginosa reduced these oxides slowly and was unable to grow anaerobically at the expense of nitrous oxide. Furthermore, nitric and nitrous oxide reduction by Pseudomonas aeruginosa were exceptionally sensitive to inhibition by nitrite. Thus, although it has been well studied physiologically and genetically, Pseudomonas aeruginosa may not be the best species for studying the later steps of the denitrification pathway.     

The Effect of Phylogenetically Different Bacteria on the Fitness of Pseudomonas fluorescens in Sand Microcosms

In most environments many microorganisms live in close vicinity and can interact in various ways. Recent studies suggest that bacteria are able to sense and respond to the presence of neighbouring bacteria in the environment and alter their response accordingly. This ability might be an important strategy in complex habitats such as soils, with great implications for shaping the microbial community structure. Here, we used a sand microcosm approach to investigate how Pseudomonas fluorescens Pf0-1 responds to the presence of monocultures or mixtures of two phylogenetically different bacteria, a Gram-negative (Pedobacter sp. V48) and a Gram-positive (Bacillus sp. V102) under two nutrient conditions. Results revealed that under both nutrient poor and nutrient rich conditions confrontation with the Gram-positive Bacillus sp. V102 strain led to significant lower cell numbers of Pseudomonas fluorescens Pf0-1, whereas confrontation with the Gram-negative Pedobacter sp. V48 strain did not affect the growth of Pseudomonas fluorescens Pf0-1. However, when Pseudomonas fluorescens Pf0-1 was confronted with the mixture of both strains, no significant effect on the growth of Pseudomonas fluorescens Pf0-1 was observed. Quantitative real-time PCR data showed up-regulation of genes involved in the production of a broad-spectrum antibiotic in Pseudomonas fluorescens Pf0-1 when confronted with Pedobacter sp. V48, but not in the presence of Bacillus sp. V102. The results provide evidence that the performance of bacteria in soil depends strongly on the identity of neighbouring bacteria and that inter-specific interactions are an important factor in determining microbial community structure.     

Assignment of<Emphasis Type="Italic"> Pseudomonas</Emphasis> sp. strain E-3 to<Emphasis Type="Italic"> Pseudomonas psychrophila</Emphasis> sp. nov., a new facultatively psychrophilic bacterium

A facultatively psychrophilic bacterium, previously described as Pseudomonas sp. strain E-3, has been reassigned by phenotypic characterization, chemotaxonomic analysis, DNA-DNA hybridization, and 16S rRNA gene phylogenetic analysis. The organism was a gram-negative, aerobic. straight rod with polar flagella. It was catalase positive and oxidase positive, able to grow at -1 degree C but not at 40 degree C, and produced acid from D-glucose under aerobic conditions. The major isoprenoid quinone was ubiquinone-9, and the DNA G + C content was 57.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the bacterium is a member of the genus Pseudomonas and was closest to Pseudomonas fragi. Determination of the DNA-DNA relatedness between strain E-3 and P. fragi revealed too low a level of homology (47.9%-51.3%) to identify them as the same species. On the basis of phenotypic characteristics, phylogenetic analysis, and DNA-DNA relatedness data, it is concluded that strain E-3 represents an individual species. Accordingly, the name Pseudomonas psychrophila is proposed. The type strain is E-3T (= JCM 10889).     

In situ – Phaseolotoxinproduktion durch permeabilisierte und immobilisierte Zellen von Pseudomonas syringae pv. phaseolicola

Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight disease of bean (Phaseolus vulgaris) produces Phaseolotoxin (N^δ-(N′-sulpho-diaminophosphinyl)-L-ornithyl-alanyl-homoarginine) — a phytotoxic secondary metabolite — under laboratory conditions in a synthetic medium. Permeabilized (EDTA-treatment) and immobilized (Agar Agar) cells of the bacterium are capable of producing Phaseolotoxin. Therefore an “in situ” production of this microbial phytoeffective compound using immobilized and permeabilized cells of Pseudomonas syringae pv. phaseolicola is possible.     

Role of Microcolony Formation in the Protistan Grazing Defense of the Aquatic Bacterium Pseudomonas sp. MWH1

A BSTRACTThe defense strategy of the aquatic bacterium Pseudomonas sp. MWH1 against flagellate grazing was investigated in chemostat and batch experiments. The influence of predation on the Pseudomonas population was studied in the absence and presence of a potential competitor ( Vibrio sp. CB5), as well as under starvation conditions and in a situation of unlimited growth. In the competition experiment the two bacterial strains were distinguished by immunofluorescence microscopy. When the Pseudomonas strain was cultured in the absence of the predator Ochromonas sp. DS, only mobile single cells were detectable. Grazing by this bacterivorous flagellate resulted in all experiments in the occurrence of a Pseudomonas subpopulation, which grew as floclike, suspended microcolonies. These microcolonies consisted of up to approximately 1,000 cells and were, because of their large size, protected against flagellate grazing. The microcolony subpopulation dominated the total Pseudomonas population in situations of high grazing pressure at a wide range of bacterial growth conditions. Thus, the formation of the microcolonies is interpreted as a successful grazing-defense strategy, which is effective under several growth conditions, allowing for the survival of the strain even when substrate depletion is combined with strong grazing pressure. Batch culture experiments demonstrated that the change in morphology of Pseudomonas sp. MWH1 is not controlled by growth rate, although no formation of microcolonies was observed after the addition of 0.2-&mgr;m-filtered flagellate cultures to Pseudomonas cultures, indicating that a chemical trigger released by the flagellate is not involved in the control of this defense mechanism.