BACKGROUND: Mineral iron(III) recognition by bacteria is considered a matter of debate. The peculiar surface chemistry of novel naked magnetic nanoparticles, called SAMNs (surface active maghemite nanoparticles) characterized by solvent exposed Fe(3+) sites on their surface, was exploited for studying mineral iron sensing in Pseudomonas fluorescens. METHODS: SAMNs were applied for mimicking Fe(3+) ions in solution, acting as magnetically drivable probes to evaluate putative Fe(3+) recognition sites on the microorganism surface. Culture broths and nano-bio-conjugates were characterized by UV-Vis spectroscopy and mass spectrometry. RESULTS: The whole heritage of a membrane porin (OprF) of P. fluorescens Ps_22 cells was recognized and firmly bound by SAMNs. The binding of nanoparticles to OprF porin was correlated to a drastic inhibition of a siderophore (pyoverdine) biosynthesis and to the stimulation of the production and rate of formation of a secondary siderophore. The analysis of metabolic pathways, based on P. fluorescens Ps_22 genomic information, evidenced that this putative secondary siderophore does not belong to a selection of the most common siderophores. CONCLUSIONS: In the scenario of an adhesion mechanism, it is plausible to consider OprF as the biological component deputed to the mineral iron sensing in P. fluorescens Ps_22, as well as one key of siderophore regulation. GENERAL SIGNIFICANCE: The present work sheds light on mineral iron sensing in microorganisms. Peculiar colloidal naked iron oxide nanoparticles offer a useful approach for probing the adhesion of bacterial surface on mineral iron for the identification of the specific recognition site for this iron uptake regulation in microorganisms.
- MeSH
- bakteriální adheze genetika MeSH
- magnetické nanočástice chemie MeSH
- minerály chemie metabolismus MeSH
- poriny chemie genetika metabolismus MeSH
- povrchově aktivní látky chemie MeSH
- proteiny vnější bakteriální membrány chemie genetika metabolismus MeSH
- Pseudomonas fluorescens chemie metabolismus MeSH
- železité sloučeniny chemie MeSH
- železo chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Plant beneficial microbes mediate biocontrol of diseases by interfering with pathogens or via strengthening the host. Although phytohormones, including cytokinins, are known to regulate plant development and physiology as well as plant immunity, their production by microorganisms has not been considered as a biocontrol mechanism. Here we identify the ability of Pseudomonas fluorescens G20-18 to efficiently control P. syringae infection in Arabidopsis, allowing maintenance of tissue integrity and ultimately biomass yield. Microbial cytokinin production was identified as a key determinant for this biocontrol effect on the hemibiotrophic bacterial pathogen. While cytokinin-deficient loss-of-function mutants of G20-18 exhibit impaired biocontrol, functional complementation with cytokinin biosynthetic genes restores cytokinin-mediated biocontrol, which is correlated with differential cytokinin levels in planta. Arabidopsis mutant analyses revealed the necessity of functional plant cytokinin perception and salicylic acid-dependent defence signalling for this biocontrol mechanism. These results demonstrate microbial cytokinin production as a novel microbe-based, hormone-mediated concept of biocontrol. This mechanism provides a basis to potentially develop novel, integrated plant protection strategies combining promotion of growth, a favourable physiological status and activation of fine-tuned direct defence and abiotic stress resilience.
- MeSH
- Arabidopsis mikrobiologie MeSH
- cytokininy analýza biosyntéza farmakologie MeSH
- kyselina salicylová farmakologie MeSH
- listy rostlin mikrobiologie MeSH
- nemoci rostlin mikrobiologie MeSH
- Pseudomonas fluorescens metabolismus MeSH
- Pseudomonas syringae účinky léků růst a vývoj patogenita MeSH
- regulátory růstu rostlin farmakologie MeSH
- tandemová hmotnostní spektrometrie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Pseudomonas fluorescens is a well-known food spoiler, able to cause serious economic losses in the food industry due to its ability to produce many extracellular, and often thermostable, compounds. The most outstanding spoilage events involving P. fluorescens were blue discoloration of several food stuffs, mainly dairy products. The bacteria involved in such high-profile cases have been identified as belonging to a clearly distinct phylogenetic cluster of the P. fluorescens group. Although the blue pigment has recently been investigated in several studies, the biosynthetic pathway leading to the pigment formation, as well as its chemical nature, remain challenging and unsolved points. In the present paper, genomic and transcriptomic data of 4 P. fluorescens strains (2 blue-pigmenting strains and 2 non-pigmenting strains) were analyzed to evaluate the presence and the expression of blue strain-specific genes. In particular, the pangenome analysis showed the presence in the blue-pigmenting strains of two copies of genes involved in the tryptophan biosynthesis pathway (including trpABCDF). The global expression profiling of blue-pigmenting strains versus non-pigmenting strains showed a general up-regulation of genes involved in iron uptake and a down-regulation of genes involved in primary metabolism. Chromogenic reaction of the blue-pigmenting bacterial cells with Kovac's reagent indicated an indole-derivative as the precursor of the blue pigment. Finally, solubility tests and MALDI-TOF mass spectrometry analysis of the isolated pigment suggested that its molecular structure is very probably a hydrophobic indigo analog.
- MeSH
- biologické pigmenty genetika MeSH
- down regulace MeSH
- energetický metabolismus genetika MeSH
- fenotyp MeSH
- fylogeneze MeSH
- genomika MeSH
- mléčné výrobky mikrobiologie MeSH
- oxidoreduktasy genetika MeSH
- potravinářská mikrobiologie * MeSH
- Pseudomonas fluorescens genetika metabolismus MeSH
- spotřeba kyslíku genetika MeSH
- stanovení celkové genové exprese MeSH
- transkriptom genetika MeSH
- tryptofan biosyntéza MeSH
- upregulace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Esterases are widely used in food processing industry, but there is little information concerning enzymes involved in decompositions of esters contributing to pollution of environment. Vinyl acetate (an ester of vinyl alcohol and acetic acid) is a representative of volatile organic compounds (VOCs) in decomposition, of which hydrolyses and oxidoreductases are mainly involved. Their activities under periodically changing conditions of environment are essential for the removal of dangerous VOCs. Esterase and alcohol/aldehyde dehydrogenase activities were determined in crude cell extract from Pseudomonas fluorescens PMC 2123 after vinyl acetate induction. All examined enzymes exhibit their highest activity at 30-35 °C and pH 7.0-7.5. Esterase preferably hydrolyzed ester bonds with short fatty chains without plain differences for C2 or C4. Comparison of Km values for alcohol and aldehyde dehydrogenases for acetaldehyde suggested that this metabolite was preferentially oxidized than reduced. Activity of alcohol dehydrogenase reducing acetaldehyde to ethanol suggested that one mechanism of defense against the elevated concentration of toxic acetaldehyde could be its temporary reduction to ethanol. Esterase activity was inhibited by phenylmethanesulfonyl fluoride, while β-mercaptoethanol, dithiothreitol, and ethylenediaminetetraacetic acid had no inhibitor effect. From among metal ions, only Mg(2+) and Fe(2+) stimulated the cleavage of ester bond.
- MeSH
- aktivátory enzymů analýza MeSH
- biotransformace MeSH
- esterasy chemie metabolismus MeSH
- inhibitory enzymů analýza MeSH
- kinetika MeSH
- koncentrace vodíkových iontů MeSH
- oxidoreduktasy chemie metabolismus MeSH
- Pseudomonas fluorescens enzymologie metabolismus MeSH
- stabilita enzymů MeSH
- teplota MeSH
- vinylové sloučeniny metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The aim of this work was to compare denitrification activity of three types of encapsulated biomass containing pure culture of Paracoccus denitrificans or Pseudomonas fluorescens or mixed culture of psychrophilic denitrifiers cultivated at 5 °C from activated sludge. The experiments were held with synthetic wastewater containing 50 mg L(-1) N-NO(3)(-) under the temperature 15, 10, 8 and 5 °C. Specific denitrification rates related to the weight of pellets and to the protein content were calculated and the temperature coefficients describing the dependence of denitrification rate on the temperature were determined. Although the mixed culture showed the highest denitrification rate at the temperatures below 10 °C, using of pellets containing pure culture is recommended as the mixed culture has slow growth rate and its activity at temperatures above 10 °C is very low.
- MeSH
- čištění vody metody MeSH
- denitrifikace fyziologie MeSH
- měření biologické spotřeby kyslíku MeSH
- nízká teplota MeSH
- odpad tekutý - odstraňování metody MeSH
- Paracoccus denitrificans metabolismus MeSH
- Pseudomonas fluorescens metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
Seven hypotheses on relationships between the structure of naphthalene analogs and bioluminescence response of bioreporter Pseudomonas fluorescens were formulated using GUHA (General Unary Hypotheses Automaton) on a training set of 37 compounds. Prediction of bioluminescence response of 12 new naphthalene analogs was successful in 69 % cases and resulted in rejection of single hypothesis. The results demonstrate applicability of GUHA in structure-activity research, especially for qualitative data.
- MeSH
- biosenzitivní techniky MeSH
- financování organizované MeSH
- luminiscenční měření MeSH
- naftaleny farmakologie chemie metabolismus MeSH
- Pseudomonas fluorescens metabolismus účinky léků MeSH
- reportérové geny MeSH
- vztahy mezi strukturou a aktivitou MeSH
- zelené fluorescenční proteiny genetika metabolismus MeSH
- MeSH
- biodegradace MeSH
- Burkholderia cepacia genetika metabolismus MeSH
- finanční podpora výzkumu jako téma MeSH
- genetické inženýrství MeSH
- katecholy metabolismus MeSH
- polychlorované bifenyly metabolismus MeSH
- Pseudomonas fluorescens genetika metabolismus MeSH
- sloučeniny chloru metabolismus MeSH
- techniky in vitro MeSH
- MeSH
- biodegradace MeSH
- farmakokinetika MeSH
- formaldehyd chemie toxicita MeSH
- Pseudomonas fluorescens metabolismus MeSH
- Publikační typ
- přehledy MeSH
