Influence of Temperature on Steady-State Growth of Colonies of Pseudomonas fluorescens

Diameters of surface colonies of Pseudomonas fluorescens were observed to increase linearly with time at temperatures from 30 to 0 C.     

Influence of Temperature on Substrate and Energy Conversion in Pseudomonas fluorescens

The influence of temperature on yield, maintenance rate, growth rate, and conversion of calories to biomass was studied with Pseudomonas fluorescens grown in a chemostat. Maintenance and growth rate are influenced linearly with temperature. Both rates increased with increasing temperature and gave linear Arrhenius plots over a limited range. Cells harvested during the steady-state at each temperature were burned in a microcalorimeter. The number of kilocalories per gram (dry weight) of organism was not influenced significantly by the temperature during growth, indicating that the conversion of substrate calories into biomass is apparently regulated in the range of temperature studied.     

Measurement of Glucose Utilization by Pseudomonas fluorescens That Are Free-Living and That Are Attached to Surfaces

The assimilation and respiration of glucose by attached and free-living Pseudomonas fluorescens were compared. The attachment surfaces were polyvinylidene fluoride, polyethylene, and glass. Specific uptake of [¹⁴C]glucose was determined after bacterial biomass was measured by (i) microscopic counts or (ii) prelabeling of cells by providing [³H]leucine as substrate, followed by dual-labeling scintillation counting. The glucose concentration was 1.4, 3.5, 5.5, 7.6, or 9.7 μM. Glucose assimilation by cells which became detached from the surfaces during incubation with glucose was also measured after the detached cells were collected by filtration. The composition of the substratum had no effect on the amount of glucose assimilated by attached cells. Glucose assimilation by attached cells exceeded that by free-living cells by a factor of between 2 and 5 or more, and respiration of glucose by surface-associated cells was greater than that by free-living bacteria. Glucose assimilation by detached cells was greater than that by attached bacteria. Measurements of biomass by microscopic counts gave more consistent results that those obtained with dual-labeling, but in general, results obtained by both methods were corroborative.     

Glucose uptake and phosphorylation in Pseudomonas fluorescens

Pseudomonas fluorescens ATCC 13525 and a particulate glucose oxidase (d-glucose:oxygen oxidoreductase, EC 1.1.3.4) mutant of this organism, gox-7, were examined to determine if glucose oxidation via particulate glucose oxidase is a required first step for glucose uptake. Initial [(14)C]glucose-uptake rates in parent and gox-7 cells were qualitatively similar. Initial [(14)C]glucose-uptake product analysis revealed that glucose was accumulated via active transport and was rapidly metabolized to glucose-6-phosphate and gluconate-6-phosphate in both parent and gox-7 cells. Cell extracts contained soluble adenosine 5'-triphosphate specific kinase activity for phosphorylation of glucose. Glucose uptake was induced by glucose and not gluconate, thus, establishing independent regulation of glucose transport and glucose catabolism in p. fluorescens. The results prove that glucose oxidase was not an obligatory reaction for glucose carbon permeation in P. fluorescens. A general unifying scheme for glucose utilization in the aerobic fluorescent pseudomonads is suggested for the purpose of clarifying glucose uptake in these bacteria.     

Gluconate Regulation of Glucose Catabolism in Pseudomonas fluorescens

Induction of Entner-Doudoroff pathway enzymes in Pseudomonas fluorescens was investigated to study the role of gluconate as a possible inducer. Glucose oxidase-deficient mutants were isolated and characterized. One of these mutants, gox-7, was deficient in particulate glucose oxidase; another mutant, gox-17, was deficient in particulate glucose and gluconate oxidase activities. Gluconate, but not glucose, induced synthesis of gluconokinase and 6-phosphogluconate dehydratase in both mutants. High constitutive levels of 2-keto-3-deoxy-6-phosphogluconate aldolase were found when both mutants were grown on glucose. Growth of parent and both mutant strains on glycerol also resulted in high levels of Entner-Doudoroff pathway enzymes. It was concluded that glucose cannot serve as an inducer molecule for derepression of Entner-Doudoroff pathway enzymes in P. fluorescens. Evidence presented provides good support for gluconate being the true inducer of this pathway in P. fluorescens. A relationship is presented for explaining distribution of the Entner-Doudoroff pathway in certain groups of bacteria.     

Utilization of a Stable Isotope of Oxygen by Pseudomonas fluorescens

Oxygen utilization is defined in this investigation as the terminal use of oxygen in respiration, i.e., the formation of water. A culture of Pseudomonas fluorescens was allowed to respire in an atmosphere of O¹⁸. The production of H₂O¹⁸ was measured during two test runs of 124 and 232 min each. During the first run, 0.505 mmole of H₂O¹⁸ was produced. The second run produced 0.460 mmole of H₂O¹⁸. H₂O¹⁸ production took place throughout the course of each of the runs.     

Influence of magnesium ions on biofilm formation by Pseudomonas fluorescens

Mg²⁺ can potentially influence bacterial adhesion directly through effects on electrostatic interactions and indirectly by affecting physiology-dependent attachment processes. However, the effects of Mg²⁺ on biofilm structure are largely unknown. In this study, Pseudomonas fluorescens was used to investigate the influence of Mg²⁺ concentration (0, 0.1 and 1.0 mM MgCl₂) on biofilm growth. Planktonic and attached cells were enumerated (based on DAPI staining) while biofilm structures were examined via confocal laser scanning microscopy and three-dimensional structures were reconstructed. Mg²⁺ concentration had no influence on growth of planktonic cells but, during biofilm formation, Mg²⁺ increased the abundance of attached cells. For attached cells, the influence of Mg²⁺ concentration changed over time, suggesting that the role of Mg²⁺ in bacterial attachment is complex and dynamic. Biofilm structures were heterogeneous and surface colonization and depth increased with increasing Mg²⁺ concentrations. Overall, for P. fluorescens, Mg²⁺ increased initial attachment and altered subsequent biofilm formation and structure.     

Glucose sensor using immobilized whole cells of Pseudomonas fluorescens

Summary Whole cells of Pseudomonas fluorescens which utilized mainly glucose were immobilized in collagen membrane. The microbial electrode consisted of a bacteria-collagen membrane and an oxygen electrode was developed for the determination of glucose. When the electrode was inserted in a sample solution containing glucose, the current of the electrode decreased markedly with time until a steady state was reached. The response time of the electrode was 10 min by the steady state method. A linear relationship was observed between the steady state current and the concentration of glucose below 20 mg l ^–1. The minimum concentration for determination was 2 mg of glucose per liter. The reproducibility of the current was examined using the same sample solution. The current was reproducible within ±6% of the relative error when a sample solution containing 10 mg {ie343-1} of glucose was employed. The standard deviation was 0.6 mg {ie343-2} in 20 experiments. The reusability of the glucose sensor was examined using the same sample solution (10 mg {ie343-3}). No decrease in current output was observed over a two week period and 150 assays. Glucose in molasses was determined with an average relative error of 10% by the microbial electrode sensor.     

Temperature regulation of lipase secretion by Pseudomonas fluorescens strain MFO

The psychrotrophic bacterium Pseudomonas fluorescens is a milk contaminant known to secrete a lipase that is a nuisance for the dairy industry but may have a biotechnological interest. Strain MFO secretes this enzyme upon induction under various conditions. Regardless of the inducer and growth temperature, a single enzyme is produced. However, optimal production occurs when the culture is grown at 17.5° C. Other exported proteins (an extracellular protease and two periplasmic phosphatases) have previously been shown to display exactly the same optimal temperature of production. In contrast, constitutive cell-bound esterase and cytochrome oxidase are produced at a roughly constant rate regardless of the growth temperature. The relevance of these results are discussed in terms of multifunctional regulation and interest for the dairy industry. Correspondence to: N. Orange     

Influence of pressure on growth of Pseudomonas fluorescens

Summary The effect of increased pressure on the growth of the bacterium Pseudomonas fluorescens has been investigated in an airlift-fermenter (10 l) up to 8 bars. It could be established, that increased hydrostatic pressure has a strong effect on the metabolism of the bacterium.     

松材线虫携带一株荧光假单胞菌分泌毒素的初步研究

本文研究了离体情况下松材线虫携带的致病菌一株荧光假单胞菌(Pseudomonas fluorescens GcM5-1A)在LB、NB和PD三种培养基中的毒性, 以及产生的毒素对黑松(Pinus thunbergii)切根苗和悬浮细胞的效应。结果显示, 菌体在LB和NB 培养液的毒性较高, 其中 LB培养液的毒性最高, 且培养液的pH值为7时比pH值为5时毒性高, 而该菌在PD培养基中几乎不产毒。细菌培养液经硫酸铵分级沉淀, 得到了主要含有50 kDa蛋白的蛋白组分, 该蛋白组分对黑松悬浮细胞和切根苗均有较高的毒性, 并能改变黑松悬浮细胞细胞膜的透性, 导致胞内可溶性糖和游离氨基酸外渗。     

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.     

Preferential Utilization of Aromatic Compounds over Glucose by Pseudomonas putida CSV86

Pseudomonas putida CSV86, a naphthalene-degrading organism, exhibited diauxic growth on aromatic compounds plus glucose, with utilization of aromatics in the first log phase and of glucose in the second log phase. Glucose supplementation did not suppress the activity of degrading enzymes, which were induced upon addition of aromatic compounds. The induction was inhibited by chloramphenicol, suggesting that de novo protein synthesis was essential. Cells showed cometabolism of aromatic compounds and organic acids; however, organic acids suppressed glucose utilization.     

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa.

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.     

Utilization of benzylpenicillin as carbon,nitrogen and energy source by a Pseudomonas fluorescens strain

A bacterium which utilizes benzylpenicillin as carbon, nitrogen and energy source was isolated from a lake sediment. The organism was identified as a strain of Pseudomonas fluorescens with a GC content of 59.71 Mol %. After growth of the organism on a mineral salts medium containing benzylpenicillin, the derivatives benzylpenicilloic acid, benzylpenilloic acid and benzylpenicillenic acid were found in culture media. There was no indication that the phenylacetate side chain of benzylpenicillin is decomposed. In uninoculated culture media benzylpenicillin, benzylpenicilloic acid and benzylpenicillenic acid were demonstrable. The following compounds were found to be absent from inoculated or uninoculated culture fluids: d-penicillamine, l-valine, l-cysteine, benzylpenillic acid and 6-aminopenicillanic acid. The organism possesses penicillinase. Penicillin acylase was not demonstrable. The reaction product of penicillinase, benzylpenicilloic acid, supports only little growth. There is no growth on 6-aminopenicillanic acid with or without NH₄Cl. Relatively little growth occurs on 6-aminopenicillanic acid in the presence of phenylacetic acid.The data indicate that the nucleus of the benzylpenicillin molecule is utilized as carbon, nitrogen and energy source. During growth a part of the substrate is destroyed into scarcely usable benzylpenicilloic acid; hereby the antibiotic is detoxified.Abbreviations TLC thin-layer chromatography - DNPH 2,4-dinitrophenylhydrazine     

Utilization of pyrazine-2-carboxamide and pyrazine-2-carboxylic acid by Pseudomonas fluorescens UK-1

Abstract Pseudomonas fluorescens strain UK-1 is capable to convert pyrazine-2-carboxamide to pyrazine-2-carboxylic acid and the latter to pyrazine. The resulting product can be detected in the growth medium. Glucose greatly enhanced the degradation. However, the cells survived and degraded the compounds also in the absence of glucose but very slowly. The utilization of a pyrazine compound and the appearance of its splitting product in the growth medium was followed as a function of time. The degradation products of unsubstituted pyrazine could not be detected.