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Applied and Environmental Microbiology Jul 2008Iron (Fe) is a critical element in all aerobic organisms as it participates in a variety of metabolic networks. In this study, aluminum (Al) and gallium (Ga), two Fe...
Iron (Fe) is a critical element in all aerobic organisms as it participates in a variety of metabolic networks. In this study, aluminum (Al) and gallium (Ga), two Fe mimetics, severely impeded the ability of the soil microbe Pseudomonas fluorescens to perform oxidative phosphorylation. This was achieved by disrupting the activity and expression of complexes I, II, and IV. These toxic metals also inactivated aconitase (ACN) and fumarase A (FUM A), two tricarboxylic acid cycle enzymes dependent on Fe for their catalytic activity, while FUM C, an Fe-independent enzyme, displayed an increase in activity and expression under these stressed situations. Furthermore, in the Al- and Ga-exposed cells, the activity and expression of an H(2)O-forming NADH oxidase were markedly increased. The incubation of the Al- and Ga-challenged cells in an Fe-containing medium led to the recovery of the affected enzymatic activities. Taken together, these data provide novel insights into how environmental pollutants such as Al and Ga interfere with cellular Fe metabolism and also illustrate the ability of Pseudomonas fluorescens to modulate metabolic networks to combat this situation.
Topics: Adaptation, Physiological; Aluminum; Culture Media; Environmental Pollutants; Fumarate Hydratase; Gallium; Gene Expression Regulation, Bacterial; Iron; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Pseudomonas fluorescens
PubMed: 18469122
DOI: 10.1128/AEM.02702-07 -
Scientific Reports Aug 2015Protozoan predation of bacteria can significantly affect soil microbial community composition and ecosystem functioning. Bacteria possess diverse defense strategies to...
Protozoan predation of bacteria can significantly affect soil microbial community composition and ecosystem functioning. Bacteria possess diverse defense strategies to resist or evade protozoan predation. For soil-dwelling Pseudomonas species, several secondary metabolites were proposed to provide protection against different protozoan genera. By combining whole-genome transcriptome analyses with (live) imaging mass spectrometry (IMS), we observed multiple changes in the molecular and chemical dialogues between Pseudomonas fluorescens and the protist Naegleria americana. Lipopeptide (LP) biosynthesis was induced in Pseudomonas upon protozoan grazing and LP accumulation transitioned from homogeneous distributions across bacterial colonies to site-specific accumulation at the bacteria-protist interface. Also putrescine biosynthesis was upregulated in P. fluorescens upon predation. We demonstrated that putrescine induces protozoan trophozoite encystment and adversely affects cyst viability. This multifaceted study provides new insights in common and strain-specific responses in bacteria-protozoa interactions, including responses that contribute to bacterial survival in highly competitive soil and rhizosphere environments.
Topics: Lipopeptides; Naegleria; Pseudomonas fluorescens; Putrescine; Transcriptome
PubMed: 26246193
DOI: 10.1038/srep12837 -
Applied and Environmental Microbiology Sep 2013Pseudomonas species can exhibit phenotypic variation resulting from gacS or gacA mutation. P. fluorescens Pf0-1 is a gacA mutant and exhibits pleiotropic changes...
Pseudomonas species can exhibit phenotypic variation resulting from gacS or gacA mutation. P. fluorescens Pf0-1 is a gacA mutant and exhibits pleiotropic changes following the introduction of a functional allele. GacA enhances biofilm development while reducing dissemination in soil, suggesting that alternative Gac phenotypes enable Pseudomonas sp. to exploit varied environments.
Topics: Bacterial Proteins; Biofilms; Gene Deletion; Genetic Complementation Test; Pseudomonas fluorescens; Soil Microbiology
PubMed: 23811507
DOI: 10.1128/AEM.00819-13 -
Journal of Bacteriology Dec 1998Three global regulators are known to control antibiotic production by Pseudomonas fluorescens. A two-component regulatory system comprised of the sensor kinase GacS...
Three global regulators are known to control antibiotic production by Pseudomonas fluorescens. A two-component regulatory system comprised of the sensor kinase GacS (previously called ApdA or LemA) and GacA, a member of the FixJ family of response regulators, is required for antibiotic production. A mutation in rpoS, which encodes the stationary-phase sigma factor sigmaS, differentially affects antibiotic production and reduces the capacity of stationary-phase cells of P. fluorescens to survive exposure to oxidative stress. The gacA gene of P. fluorescens Pf-5 was isolated, and the influence of gacS and gacA on rpoS transcription, sigmaS levels, and oxidative stress response of Pf-5 was determined. We selected a gacA mutant of Pf-5 that contained a single nucleotide substitution within a predicted alpha-helical region, which is highly conserved among the FixJ family of response regulators. At the entrance to stationary phase, sigmaS content in gacS and gacA mutants of Pf-5 was less than 20% of the wild-type level. Transcription of rpoS, assessed with an rpoS-lacZ transcriptional fusion, was positively influenced by GacS and GacA, an effect that was most evident at the transition between exponential growth and stationary phase. Mutations in gacS and gacA compromised the capacity of stationary-phase cells of Pf-5 to survive exposure to oxidative stress. The results of this study provide evidence for the predominant roles of GacS and GacA in the regulatory cascade controlling stress response and antifungal metabolite production in P. fluorescens.
Topics: Alleles; Bacterial Proteins; Base Sequence; DNA, Bacterial; Gene Expression Regulation, Bacterial; Genes, Regulator; Hydrogen Peroxide; Lac Operon; Molecular Sequence Data; Oxidative Stress; Phenotype; Pseudomonas fluorescens; Sequence Analysis, DNA; Sigma Factor; Transcription Factors; Transcription, Genetic; Transposases
PubMed: 9852008
DOI: 10.1128/JB.180.24.6635-6641.1998 -
Applied and Environmental Microbiology Dec 2001A variety of stress situations may affect the activity and survival of plant-beneficial pseudomonads added to soil to control root diseases. This study focused on the...
The sigma factor AlgU (AlgT) controls exopolysaccharide production and tolerance towards desiccation and osmotic stress in the biocontrol agent Pseudomonas fluorescens CHA0.
A variety of stress situations may affect the activity and survival of plant-beneficial pseudomonads added to soil to control root diseases. This study focused on the roles of the sigma factor AlgU (synonyms, AlgT, RpoE, and sigma(22)) and the anti-sigma factor MucA in stress adaptation of the biocontrol agent Pseudomonas fluorescens CHA0. The algU-mucA-mucB gene cluster of strain CHA0 was similar to that of the pathogens Pseudomonas aeruginosa and Pseudomonas syringae. Strain CHA0 is naturally nonmucoid, whereas a mucA deletion mutant or algU-overexpressing strains were highly mucoid due to exopolysaccharide overproduction. Mucoidy strictly depended on the global regulator GacA. An algU deletion mutant was significantly more sensitive to osmotic stress than the wild-type CHA0 strain and the mucA mutant were. Expression of an algU'-'lacZ reporter fusion was induced severalfold in the wild type and in the mucA mutant upon exposure to osmotic stress, whereas a lower, noninducible level of expression was observed in the algU mutant. Overexpression of algU did not enhance tolerance towards osmotic stress. AlgU was found to be essential for tolerance of P. fluorescens towards desiccation stress in a sterile vermiculite-sand mixture and in a natural sandy loam soil. The size of the population of the algU mutant declined much more rapidly than the size of the wild-type population at soil water contents below 5%. In contrast to its role in pathogenic pseudomonads, AlgU did not contribute to tolerance of P. fluorescens towards oxidative and heat stress. In conclusion, AlgU is a crucial determinant in the adaptation of P. fluorescens to dry conditions and hyperosmolarity, two major stress factors that limit bacterial survival in the environment.
Topics: Adaptation, Physiological; Bacterial Proteins; Cloning, Molecular; Desiccation; Fungi; Gene Expression Regulation, Bacterial; Molecular Sequence Data; Osmotic Pressure; Pest Control, Biological; Polysaccharides, Bacterial; Pseudomonas fluorescens; Sequence Analysis, DNA; Sigma Factor
PubMed: 11722923
DOI: 10.1128/AEM.67.12.5683-5693.2001 -
Applied and Environmental Microbiology Dec 1995We investigated the survival, cell length, and development of general stress resistance in populations of Pseudomonas fluorescens R2f and its rifampin-resistant mutant,...
We investigated the survival, cell length, and development of general stress resistance in populations of Pseudomonas fluorescens R2f and its rifampin-resistant mutant, R2f Rpr, following exposure to carbon starvation conditions in liquid cultures and residence in two different soils, Flevo silt loam (FSL) and Ede loamy sand (ELS). In much the same way as was recently shown for P. putida KT2442, carbon-starved P. fluorescens R2f populations revealed enhanced resistance to otherwise lethal treatments, such as exposure to ethanol, high temperature, osmotic tension, and oxidative stress. A large population of nonculturable P. fluorescens R2f Rpr cells arose shortly after their introduction into ELS soil, whereas the formation of nonculturable cells was not observed in FSL soil. Also, the inoculant cell (based on immunofluorescence) and CFU counts decreased faster in ELS soil than in FSL soil. Introduction of carbon-starved instead of exponential-growth-phase R2f Rpr cells into ELS soil did not affect bacterial survival. The inoculant cell length decreased in soil, and no large differences in cell length in the two soil types were observed. Addition of glucose to ELS soil resulted in a stable cell length of R2f Rpr cells, whereas carbon-starved cells introduced into ELS soil remained small. Exponentially growing R2f Rpr cells developed enhanced resistance to ethanol, high temperature, osmotic tension, and oxidative stress within 1 day in both soils, whereas cells introduced into ELS soil amended with glucose showed decreased resistance. Cells that were carbon starved prior to introduction into ELS soil showed unchanged stress resistance levels upon residence in soil.
Topics: Carbon; Drug Resistance, Microbial; Mutation; Oxidative Stress; Pseudomonas fluorescens; Rifampin; Soil Microbiology
PubMed: 8534087
DOI: 10.1128/aem.61.12.4202-4208.1995 -
Langmuir : the ACS Journal of Surfaces... Jun 2023Microbial adhesion and spreading on surfaces are crucial aspects in environmental and industrial settings being also the early stage of complex surface-attached...
Microbial adhesion and spreading on surfaces are crucial aspects in environmental and industrial settings being also the early stage of complex surface-attached microbial communities known as biofilms. In this work, -laden droplets on hydrophilic substrates (glass coupons) are allowed to partially evaporate before running wetting measurements, to study the effect of evaporation on their interfacial behavior during spillover or splashing. Forced wetting is investigated by imposing controlled centrifugal forces, using a novel rotatory device (). At a defined evaporation time, results for the critical tangential force required for the inception of sliding are presented. Microbe-laden droplets exhibit different wetting/spreading properties as a function of the imposed evaporation times. It is found that evaporation is slowed down in bacterial droplets with respect to nutrient medium ones. After sufficient drying times, bacteria accumulate at droplet edges, affecting the droplet shape and thus depinning during forced wetting tests. Droplet rear part does not pin during the rotation test, while only the front part advances and spreads along the force direction. Quantitative results obtained from the well-known Furmidge's equation reveal that force for sliding inception increases as evaporation time increases. This study can be of support for control of biofilm contamination and removal and possible design of antimicrobial/antibiofouling surfaces.
Topics: Pseudomonas fluorescens; Wettability; Hydrophobic and Hydrophilic Interactions; Volatilization; Viscosity
PubMed: 37079897
DOI: 10.1021/acs.langmuir.3c00179 -
ELife Oct 2021Common garden experiments that inoculate a standardised growth medium with synthetic microbial communities (i.e. constructed from individual isolates or using dilution...
Common garden experiments that inoculate a standardised growth medium with synthetic microbial communities (i.e. constructed from individual isolates or using dilution cultures) suggest that the ability of the community to resist invasions by additional microbial taxa can be predicted by the overall community productivity (broadly defined as cumulative cell density and/or growth rate). However, to the best of our knowledge, no common garden study has yet investigated the relationship between microbial community composition and invasion resistance in microcosms whose compositional differences reflect natural, rather than laboratory-designed, variation. We conducted experimental invasions of two bacterial strains ( and ) into laboratory microcosms inoculated with 680 different mixtures of bacteria derived from naturally occurring microbial communities collected in the field. Using 16S rRNA gene amplicon sequencing to characterise microcosm starting composition, and high-throughput assays of community phenotypes including productivity and invader survival, we determined that productivity is a key predictor of invasion resistance in natural microbial communities, substantially mediating the effect of composition on invasion resistance. The results suggest that similar general principles govern invasion in artificial and natural communities, and that factors affecting resident community productivity should be a focal point for future microbial invasion experiments.
Topics: Microbiota; Pseudomonas fluorescens; Pseudomonas putida
PubMed: 34662276
DOI: 10.7554/eLife.71811 -
Virologica Sinica Feb 2015
Topics: Bacteriophages; Biological Therapy; Humans; Pseudomonas Infections; Pseudomonas fluorescens
PubMed: 25595213
DOI: 10.1007/s12250-014-3490-2 -
Microbial Biotechnology Jul 2009The colonization process of Olea europaea by the defoliating pathotype of Verticillium dahliae, and the in planta interaction with the endophytic, biocontrol strain...
The colonization process of Olea europaea by the defoliating pathotype of Verticillium dahliae, and the in planta interaction with the endophytic, biocontrol strain Pseudomonas fluorescens PICF7 were determined. Differential fluorescent protein tagging was used for the simultaneous visualization of P. fluorescens PICF7 and V. dahliae in olive tissues. Olive plants were bacterized with PICF7 and then transferred to V. dahliae-infested soil. Monitoring olive colonization events by V. dahliae and its interaction with PICF7 was conducted using a non-gnotobiotic system, confocal laser scanner microscopy and tissue vibratoming sections. A yellow fluorescently tagged V. dahliae derivative (VDAT-36I) was obtained by Agrobacterium tumefaciens-mediated transformation. Isolate VDAT-36I quickly colonized olive root surface, successfully invaded root cortex and vascular tissues via macro- and micro-breakages, and progressed to the aerial parts of the plant through xylem vessel cells. Strain PICF7 used root hairs as preferred penetration site, and once established on/in root tissues, hindered pathogen colonization. For the first time using this approach, the entire colonization process of a woody plant by V. dahliae is reported. Early and localized root surface and root endophytic colonization by P. fluorescens PICF7 is needed to impair full progress of verticillium wilt epidemics in olive.
Topics: Antibiosis; Microscopy, Confocal; Olea; Plant Roots; Pseudomonas fluorescens; Verticillium
PubMed: 21255281
DOI: 10.1111/j.1751-7915.2009.00105.x