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Brazilian Journal of Microbiology :... 2017Meat is one of the most perishable foods owing to its nutrient availability, high water activity, and pH around 5.6. These properties are highly conducive for microbial...
Meat is one of the most perishable foods owing to its nutrient availability, high water activity, and pH around 5.6. These properties are highly conducive for microbial growth. Fresh meat, when exposed to oxygen, is subjected to the action of aerobic psychrotrophic, proteolytic, and lipolytic spoilage microorganisms, such as Pseudomonas spp. The spoilage results in the appearance of slime and off-flavor in food. In order to predict the growth of Pseudomonas fluorescens in fresh meat at different pH values, stored under refrigeration, and temperature abuse, microbial mathematical modeling was applied. The primary Baranyi and Roberts and the modified Gompertz models were fitted to the experimental data to obtain the growth parameters. The Ratkowsky extended model was used to determine the effect of pH and temperature on the growth parameter μ. The program DMFit 3.0 was used for model adjustment and fitting. The experimental data showed good fit for both the models tested, and the primary and secondary models based on the Baranyi and Roberts models showed better validation. Thus, these models can be applied to predict the growth of P. fluorescens under the conditions tested.
Topics: Aerobiosis; Food Microbiology; Hydrogen-Ion Concentration; Meat; Models, Theoretical; Pseudomonas fluorescens; Temperature
PubMed: 28110805
DOI: 10.1016/j.bjm.2016.12.006 -
Scientific Reports Sep 2018Bacterial motility plays a crucial role in competitiveness and colonization in the rhizosphere. In this work, Chromatin ImmunoPrecipitation Sequencing (ChIP-seq)...
Bacterial motility plays a crucial role in competitiveness and colonization in the rhizosphere. In this work, Chromatin ImmunoPrecipitation Sequencing (ChIP-seq) analysis has been used to identify genes putatively regulated by the transcriptional regulatory protein FleQ in Pseudomonas fluorescens F113 and Pseudomonas putida KT2440. This protein was previously identified as a master regulator of flagella and biofilm formation in both strains. This work has demonstrated that FleQ from both bacteria are conserved and functionally equivalent for motility regulation. Furthermore, the ChIP-seq analysis has shown that FleQ is a global regulator with the identification of 121 and 103 FleQ putative binding sites in P. fluorescens F113 and P. putida KT2440 respectively. Putative genes regulated by FleQ included, as expected, flagellar and motility-related genes and others involved in adhesion and exopolysaccharide production. Surprisingly, the ChIP-seq analysis also identified iron homeostasis-related genes for which positive regulation was shown by RT-qPCR. The results also showed that FleQ from P. fluorescens F113 shares an important part of its direct regulon with AmrZ, a global regulator also implicated in environmental adaption. Although AmrZ also regulates motility and iron uptake, the overlap occurred mostly with the iron-related genes, since both regulators control a different set of motility-related genes.
Topics: Bacterial Proteins; Binding Sites; Biofilms; Flagella; Gene Expression Regulation, Bacterial; Gene Ontology; Genome, Bacterial; Iron; Iron-Regulatory Proteins; Molecular Sequence Annotation; Movement; Protein Binding; Pseudomonas fluorescens; Pseudomonas putida; Regulon; Trans-Activators
PubMed: 30177764
DOI: 10.1038/s41598-018-31371-z -
ELife Dec 2021Agricultural soil harbors a diverse microbiome that can form beneficial relationships with plants, including the inhibition of plant pathogens. spp. are one of the most...
Agricultural soil harbors a diverse microbiome that can form beneficial relationships with plants, including the inhibition of plant pathogens. spp. are one of the most abundant bacterial genera in the soil and rhizosphere and play important roles in promoting plant health. However, the genetic determinants of this beneficial activity are only partially understood. Here, we genetically and phenotypically characterize the population in a commercial potato field, where we identify strong correlations between specialized metabolite biosynthesis and antagonism of the potato pathogens and . Genetic and chemical analyses identified hydrogen cyanide and cyclic lipopeptides as key specialized metabolites associated with inhibition, which was supported by in planta biocontrol experiments. We show that a single potato field contains a hugely diverse and dynamic population of bacteria, whose capacity to produce specialized metabolites is shaped both by plant colonization and defined environmental inputs.
Topics: Hydrogen Cyanide; Lipopeptides; Peptides, Cyclic; Phytophthora infestans; Plant Diseases; Pseudomonas fluorescens; Solanum tuberosum; Streptomyces
PubMed: 34792466
DOI: 10.7554/eLife.71900 -
Chembiochem : a European Journal of... Apr 2022Aspartate ammonia-lyases (AALs) catalyze the non-oxidative elimination of ammonia from l-aspartate to give fumarate and ammonia. In this work the AAL coding gene from...
Aspartate ammonia-lyases (AALs) catalyze the non-oxidative elimination of ammonia from l-aspartate to give fumarate and ammonia. In this work the AAL coding gene from Pseudomonas fluorescens R124 was identified, isolated, and cloned into the pET-15b expression vector and expressed in E. coli. The purified enzyme (PfAAL) showed optimal activity at pH 8.8, Michaelis-Menten kinetics in the ammonia elimination from l-aspartate, and no strong dependence on divalent metal ions for its activity. The purified PfAAL was covalently immobilized on epoxy-functionalized magnetic nanoparticles (MNP), and effective kinetics of the immobilized PfAAL-MNP was compared to the native solution form. Glycerol addition significantly enhanced the storability of PfAAL-MNP. Inhibiting effect of the growing viscosity (modulated by addition of glycerol or glucose) on the enzymatic activity was observed for the native and immobilized form of PfAAL, as previously described for other free enzymes. The storage stability and recyclability of PfAAL-MNP is promising for further biocatalytic applications.
Topics: Aspartate Ammonia-Lyase; Enzymes, Immobilized; Escherichia coli; Hydrogen-Ion Concentration; Kinetics; Magnetite Nanoparticles; Pseudomonas fluorescens
PubMed: 35114050
DOI: 10.1002/cbic.202100708 -
Japanese Journal of Infectious Diseases Nov 2022Monomicrobial necrotizing fasciitis caused by Pseudomonas species is a rare infection. This study aimed to elucidate the specific characteristics and clinical outcomes...
Monomicrobial necrotizing fasciitis caused by Pseudomonas species is a rare infection. This study aimed to elucidate the specific characteristics and clinical outcomes of necrotizing fasciitis caused by Pseudomonas aeruginosa and Pseudomonas fluorescens. Ten patients with monomicrobial necrotizing fasciitis caused by Pseudomonas species were retrospectively reviewed in an 8-year period. Differences in mortality, patient characteristics, clinical presentation, laboratory data, and clinical outcomes were compared between the death and survival groups. Two patients died, showing a mortality rate of 20%. P. aeruginosa was the causative agent in nine patients and P. fluorescens in one patient. The most common comorbidity was type 2 diabetes (n = 5). We found that patients who died had lower albumin levels and higher leukocyte counts than those who survived. Monomicrobial necrotizing fasciitis caused by Pseudomonas species needs emergent surgical intervention and aggressive intensive care due to the high mortality rate. We report the first case of monomicrobial necrotizing fasciitis caused by P. fluorescens. Severe hypoalbuminemia and high leukocyte counts in initial laboratory examinations can be considered poor prognostic factors.
Topics: Humans; Fasciitis, Necrotizing; Pseudomonas aeruginosa; Pseudomonas fluorescens; Retrospective Studies; Diabetes Mellitus, Type 2; Sepsis
PubMed: 35908872
DOI: 10.7883/yoken.JJID.2022.087 -
Applied and Environmental Microbiology May 2015Iron is essential in many biological processes. However, its bioavailability is reduced in aerobic environments, such as soil. To overcome this limitation,...
Iron is essential in many biological processes. However, its bioavailability is reduced in aerobic environments, such as soil. To overcome this limitation, microorganisms have developed different strategies, such as iron chelation by siderophores. Some bacteria have even gained the ability to detect and utilize xenosiderophores, i.e., siderophores produced by other organisms. We illustrate an example of such an interaction between two soil bacteria, Pseudomonas fluorescens strain BBc6R8 and Streptomyces ambofaciens ATCC 23877, which produce the siderophores pyoverdine and enantiopyochelin and the siderophores desferrioxamines B and E and coelichelin, respectively. During pairwise cultures on iron-limiting agar medium, no induction of siderophore synthesis by P. fluorescens BBc6R8 was observed in the presence of S. ambofaciens ATCC 23877. Cocultures with a Streptomyces mutant strain that produced either coelichelin or desferrioxamines, as well as culture in a medium supplemented with desferrioxamine B, resulted in the absence of pyoverdine production; however, culture with a double mutant deficient in desferrioxamines and coelichelin production did not. This strongly suggests that P. fluorescens BBbc6R8 utilizes the ferrioxamines and ferricoelichelin produced by S. ambofaciens as xenosiderophores and therefore no longer activates the production of its own siderophores. A screening of a library of P. fluorescens BBc6R8 mutants highlighted the involvement of the TonB-dependent receptor FoxA in this process: the expression of foxA and genes involved in the regulation of its biosynthesis was induced in the presence of S. ambofaciens. In a competitive environment, such as soil, siderophore piracy could well be one of the driving forces that determine the outcome of microbial competition.
Topics: Culture Media; Deferoxamine; Ferric Compounds; Microbial Interactions; Oligopeptides; Pseudomonas fluorescens; Siderophores; Streptomyces
PubMed: 25724953
DOI: 10.1128/AEM.03520-14 -
Microbiological Research Mar 2023Membrane cardiolipin (CL) phospholipids play a fundamental role in the adaptation of bacteria to various environmental conditions, including saline stress. Here, we...
Membrane cardiolipin (CL) phospholipids play a fundamental role in the adaptation of bacteria to various environmental conditions, including saline stress. Here, we constructed deletion mutants of two CL synthetase genes, clsA (UM270 ∆clsA) and clsB (UM270 ∆clsB), in the rhizobacterium Pseudomonas fluorescens UM270, and evaluated their role in plant growth promotion under salt stress. UM270 ∆clsA and UM270 ∆clsB mutants showed a significant reduction in CL synthesis compared to the P. fluorescens UM270 wild-type (UM270 wt) strain (58% ∆clsA and 53% ∆clsB), and their growth rate was not affected, except when grown at 100 and 200 mM NaCl. Additionally, the root colonization capacity of both mutant strains was impaired compared with that of the wild type. Concomitant with the deletion of clsA and clsB genes, some physiological changes were observed in the UM270 ∆clsA and UM270 ∆clsB mutants, such as a reduction in indole acetic acid and biofilm production. By contrast, an increase in siderophore biosynthesis was observed. Further, inoculation of the UM270 wt strain in tomato plants (Solanum lycopersicum) grown under salt stress conditions (100 and 200 mM NaCl) resulted in an increase in root and shoot length, chlorophyll content, and dry weight. On the contrary, when each of the mutants were inoculated in tomato plants, a reduction in root length was observed when grown at 200 mM NaCl, but the shoot length, chlorophyll content, and total plant dry weight parameters were significantly reduced under normal or saline conditions (100 and 200 mM NaCl), compared to UM270 wt-inoculated plants. In conclusion, these results suggest that CL synthesis in P. fluorescens UM270 plays an important role in the promotion of tomato plant growth under normal conditions, but to a greater extent, under salt-stress conditions.
Topics: Pseudomonas fluorescens; Cardiolipins; Sodium Chloride; Salt Stress; Chlorophyll; Plant Roots
PubMed: 36587534
DOI: 10.1016/j.micres.2022.127295 -
Journal of Dairy Science May 2020This study aimed to investigate the effect of different activity levels of a thermoresistant protease, produced by Pseudomonas fluorescens (ATCC 17556), on the...
This study aimed to investigate the effect of different activity levels of a thermoresistant protease, produced by Pseudomonas fluorescens (ATCC 17556), on the cheesemaking properties of milk and proteolysis levels. Sterilized reconstituted skim milk powder was inoculated with the bacteria, and after incubation, centrifuged to obtain a supernatant-containing protease. Raw milk was collected and inoculated to obtain a protease activity of 0.15, 0.60, and 1.5 U/L of milk (treatments P1, P4, and P10, respectively). One sample was not inoculated (control) and noninoculated supernatant was added to a fifth sample to be used as a negative control. Samples were stored at 4°C for 72 h. After 0, 48, and 72 h, the rennet coagulation properties and proteolysis levels were assessed. The protease produced was thermoresistant, as no significant differences were observed in the activity in the pasteurized (72°C for 15 s) and nonpasteurized supernatants. The chromatograms and electrophoretograms indicated that the protease preferably hydrolyzed κ-casein and β-casein, and levels of proteolysis increased with added protease activity over storage time. The hydrolysis of α-caseins and major whey proteins increased considerably in P10 milk samples. At 0 h, the increase in the level of protease activity decreased the rennet coagulation time (RCT, min) of the samples, possibly due to synergistic proteolysis of κ-casein into para-κ-casein. However, over prolonged storage, hydrolysis of β-casein and α-casein increased in P4 and P10 samples. The RCT of P4 samples increased over time and the coagulum became softer, whereas P10 samples did not coagulate after 48 h of storage. In contrast, the RCT of P1 samples decreased over time and a firmer coagulum was obtained, possibly due to a lower rate of hydrolysis of β-casein and α-casein. Increased levels of protease could result in further hydrolysis of caseins, affecting the processability of milk over storage time.
Topics: Animals; Caseins; Cattle; Chymosin; Hydrolysis; Milk; Pasteurization; Peptide Hydrolases; Proteolysis; Pseudomonas fluorescens; Whey Proteins
PubMed: 32147268
DOI: 10.3168/jds.2019-17771 -
Biomolecules Nov 20219 and 54, proposed as biofungicides to control , a dangerous pathogen of soybean and other crops, were grown in vitro to evaluate their ability to produce metabolites...
9 and 54, proposed as biofungicides to control , a dangerous pathogen of soybean and other crops, were grown in vitro to evaluate their ability to produce metabolites with antifungal activity. The aim of the manuscript was to identify the natural compounds responsible for their antifungal activity. Only the culture filtrates of 9 showed strong antifungal activity against . Its organic extract contained phenazine and mesaconic acid ( and ), whose antifungal activity was tested against , as well as and , other pathogens of soybean; however, only compound exhibited activity. The antifungal activity of compound was compared to phenazine-1-carboxylic acid (PCA, ), 2-hydroxyphenazine (2-OH P, ), and various semisynthetic phenazine nitro derivatives in order to perform a structure-activity relationship (SAR) study. PCA and phenazine exhibited the same percentage of growth inhibition in and , whereas PCA () showed lower activity against than phenazine. 2-Hydroxyphenazine () showed no antifungal activity against . The results of the SAR study showed that electron attractor (COOH and NO) or repulsor (OH) groups significantly affect the antifungal growth, as well as their α- or β-location on the phenazine ring. Both PCA and phenazine could be proposed as biopesticides to control the soybean pathogens , , and , and these results should prompt an investigation of their large-scale production and their suitable formulation for greenhouse and field applications.
Topics: Antifungal Agents; Ascomycota; Pseudomonas fluorescens; Glycine max
PubMed: 34827726
DOI: 10.3390/biom11111728 -
Diseases of Aquatic Organisms Jun 2015Pseudomonas fluorescens is a Gram-negative bacterium and a common pathogen to a wide range of farmed fish. In a previous study, we found that the ferric uptake regulator... (Randomized Controlled Trial)
Randomized Controlled Trial
Pseudomonas fluorescens is a Gram-negative bacterium and a common pathogen to a wide range of farmed fish. In a previous study, we found that the ferric uptake regulator gene (fur) is essential to the infectivity of a pathogenic fish isolate of P. fluorescens (wild-type strain TSS). In the present work, we conducted comparative proteomic analysis to examine the global protein profiles of TSS and the P. fluorescens fur knockout mutant TFM. Twenty-eight differentially produced proteins were identified, which belong to different functional categories. Four of these proteins, viz. TssP (a type VI secretion protein), PspA (a serine protease), OprF (an outer membrane porin), and ClpP (the proteolytic subunit of an ATP-dependent Clp protease), were assessed for virulence participation in a model of turbot Scophthalmus maximus. The results showed that the oprF and clpP knockouts exhibited significantly reduced capacities in (1) resistance against the bactericidal effect of host serum, (2) dissemination into and colonization of host tissues, and (3) inducing host mortality. In contrast, mutation of tssP and pspA had no apparent effect on the pathogenicity of TSS. Purified recombinant OprF, when used as a subunit vaccine, induced production of specific serum antibodies in immunized fish and elicited significant protection against lethal TSS challenge. Antibody blocking of the OprF in TSS significantly impaired the ability of the bacteria to invade host tissues. Taken together, these results indicate for the first time that in pathogenic P. fluorescens, Fur regulates the expression of diverse proteins, some of which are required for optimal infection.
Topics: Animals; Antibodies, Bacterial; Bacterial Proteins; Bacterial Vaccines; Cloning, Molecular; Fish Diseases; Flatfishes; Gene Deletion; Gene Expression Regulation, Bacterial; Mutation; Pseudomonas Infections; Pseudomonas fluorescens; RNA, Messenger; Rats; Virulence
PubMed: 26119301
DOI: 10.3354/dao02874