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Environmental Science and Pollution... Dec 2023Lead, a toxic heavy metal present in soil, hampers biological activities and affects the metabolism of plants, animals, and human beings. Its higher concentration may...
Lead, a toxic heavy metal present in soil, hampers biological activities and affects the metabolism of plants, animals, and human beings. Its higher concentration may disturb the various physio-chemical processes, which result in stunted and poor plant growth. An interactive approach of plant growth promoting rhizobacteria (PGPR) and L-tryptophan can be used to mitigate the lethal effects of lead. A pot experiment was conducted, and two weeks before sowing, the level of lead (300 mg kg) was maintained by spiking the PbCl salt. Pseudomonas fluorescens and L-tryptophan were applied individually as well as in combination to segregate the effect of both in contaminated soil under a completely Randomized Design (CRD). Statistical analysis revealed that plant growth was significantly reduced up to 22% due to lead contamination. However, the interactive approach of PGPR and L-tryptophan significantly improved the plant growth, physiology, and yield with relative productive index (RPI) under a lead-stressed environment. Moreover, integrated use of PGPR and L-tryptophan demonstrated a considerable increase (22%) in lead removal efficiency (LRE) by improving bioconcentration factor (BCF) and translocation factor (TF) for shoot without increasing the lead concentration in achenes. The reduced lead concentration in achene was due to its immobilization in shoot and root by negatively charged particles and improved the lead sequestration in vegetative parts which abridged the translocation of lead into achenes.
Topics: Animals; Humans; Lead; Helianthus; Pseudomonas fluorescens; Tryptophan; Biodegradation, Environmental; Alphaproteobacteria; Soil; Soil Pollutants
PubMed: 37940829
DOI: 10.1007/s11356-023-30839-4 -
The Science of the Total Environment Jan 2024Rhizobacteria maintain a healthy soil required for crop growth. This has led to increased interest in the use of bacteria-based biofertilizers in agriculture as they...
Rhizobacteria maintain a healthy soil required for crop growth. This has led to increased interest in the use of bacteria-based biofertilizers in agriculture as they improve soil nutrient content and protect plants against pathogens. However, the effect of bacteria inoculum on N transformation and soil physicochemical properties during urea fertilization remains unexploited. Thus, this study investigated the effect of Pseudomonas fluorescens on urea N transformation in an acidic Ultisol within a 70-d incubation period. The results revealed that (1) soil pH peaked on d 5 (pH 5.58) and 20 (pH 6.23) and rapidly decreased till d 62 (pH 4.10) and 50 (pH 4.93) for urea and urea + bacteria treatments, respectively, and remained constant thereafter. After 70 d, the pH of the bacteria-treated Ultisol remained higher (0.78 pH units) than that of urea-treated Ultisol; (2) the change in soil pH was in agreement with the mineralization trend of N, as the concentration of NH-N peaked on d 5 (134.2 mg N kg) and 20 (423 mg N kg) before decreasing to 62.1 and 276.1 mg N kg on d 70 in urea-treated and bacteria-treated Ultisol, respectively; and (3) P. fluorescens consumed protons produced during nitrification to retard rapid decrease in soil pH, decreased soil exchangeable acidity (33.3 %), increased soil effective cation exchange capacity (32.8 %), and increased the solubility of soil exchangeable base cations (68.4 %, Ca + Mg + K + Na). Thus, bacterial inoculum could promote N mineralization, enhance nutrient solubility, and retard soil acidification during N transformation in soils.
Topics: Pseudomonas fluorescens; Urea; Hydrogen-Ion Concentration; Soil; Cations; Crops, Agricultural; Nitrogen; Fertilizers
PubMed: 37813255
DOI: 10.1016/j.scitotenv.2023.167652 -
Journal of Dairy Science Apr 2024Biofilm formation is usually affected by many environmental factors, including divalent cations. The purpose of the current work was to analyze how calcium (Ca) affects...
Biofilm formation is usually affected by many environmental factors, including divalent cations. The purpose of the current work was to analyze how calcium (Ca) affects the biofilm formation of dairy Pseudomonas fluorescens isolates by investigating their growth, swarming motility, biofilm-forming capacity, extracellular polymeric substance production, and biofilm structures. Moreover, the regulation mechanism of Ca involved in its biofilm formation was explored through RNA-sequencing analysis. This work revealed that supplementation of 5, 10, 15, and 20 mM Ca significantly reduced the swarming motility of P. fluorescens strains (P.F, P.F, and P.F), but the biofilm-forming ability and polysaccharide production were increased after the supplementation of 5 and 10 mM Ca. By the supplementation of Ca, complex structures with more cell clusters glued together in P. fluorescens P.F biofilms were confirmed by scanning electron microscopy, and increased biomass and coverage of P. fluorescens P.F biofilms were observed by confocal laser scanning microscopy. In addition, RNA-sequencing results showed that P. fluorescens P.F showed a transcriptional response to the supplementation of 10 mM Ca, and a total of 137 genes were significantly expressed. The differential genes were represented in 4 upregulated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways (nonribosomal peptide structures, quorum sensing, biosynthesis of siderophore group nonribosomal peptides, and phenylalanine metabolism), and 4 downregulated KEGG pathways (flagellar assembly, amino sugar and nucleotide sugar metabolism, nitrotoluene degradation, and cationic antimicrobial peptide resistance). The results indicate that Ca might serve as an enhancer to substantially trigger the biofilm formation of dairy P. fluorescens isolates in the dairy industry.
Topics: Animals; Calcium; Pseudomonas fluorescens; Extracellular Polymeric Substance Matrix; Biofilms; RNA
PubMed: 37949404
DOI: 10.3168/jds.2023-23860 -
PLoS Biology Jan 2024Ecological variation influences the character of many biotic interactions, but examples of predator-prey reversal mediated by abiotic context are few. We show that the...
Ecological variation influences the character of many biotic interactions, but examples of predator-prey reversal mediated by abiotic context are few. We show that the temperature at which prey grow before interacting with a bacterial predator can determine the very direction of predation, reversing predator and prey identities. While Pseudomonas fluorescens reared at 32°C was extensively killed by the generalist predator Myxococcus xanthus, P. fluorescens reared at 22°C became the predator, slaughtering M. xanthus to extinction and growing on its remains. Beyond M. xanthus, diffusible molecules in P. fluorescens supernatant also killed 2 other phylogenetically distant species among several examined. Our results suggest that the sign of lethal microbial antagonisms may often change across abiotic gradients in natural microbial communities, with important ecological and evolutionary implications. They also suggest that a larger proportion of microbial warfare results in predation-the killing and consumption of organisms-than is generally recognized.
Topics: Animals; Predatory Behavior; Antibiosis; Biological Evolution; Microbiota; Myxococcus xanthus
PubMed: 38261596
DOI: 10.1371/journal.pbio.3002454 -
Anais Da Academia Brasileira de Ciencias 2023Pseudomonas fluorescens is known to have the ability to adhere and produce biofilm. The formation of biofilms is enhanced by cellular motility, particularly when...
Pseudomonas fluorescens is known to have the ability to adhere and produce biofilm. The formation of biofilms is enhanced by cellular motility, particularly when mediated by flagella. Biofilm formed on surfaces such as those used for food production act as points of contamination, releasing pathogenic or deteriorating microorganisms and compromising the quality of products. We assessed two strains of Pseudomonas fluorescens PL5.4 and PL7.1, sampled from raw, chilled, buffalo milk, which was obtained from a dairy farm. Twitching and swarming motility assays were performed, in addition to the biofilm production evaluations at a temperature of 7 °C. Regarding the motility assays, only the PL5.4 strain scored positive for the swarming assay. On microplates, both strains presented themselves as strong biofilm producers at 7 °C. The PL5.4 strain was also able to form biofilm on a stainless steel structure and maintain this structure for up to 72 hours at refrigeration. The Pseudomonas fluorescens PL5.4 isolate was identified on the basis of a 99% sequence identity with Pseudomonas fluorescens A506, a strain used as a biocontrol in agriculture. Biofilm-forming bacteria, when adapted to low temperatures, become a constant source of contamination, damaging the production, quality, safety and shelf-life of products.
Topics: Animals; Pseudomonas fluorescens; Milk; Biofilms; Temperature
PubMed: 37466543
DOI: 10.1590/0001-3765202320220982 -
Journal of Bacteriology Sep 2023Biofilm formation by the Gram-negative, Gammaproteobacteria relies on the repeats-in-toxin adhesins LapA and MapA in the cytoplasm, secretion of these adhesins through...
Biofilm formation by the Gram-negative, Gammaproteobacteria relies on the repeats-in-toxin adhesins LapA and MapA in the cytoplasm, secretion of these adhesins through their respective type 1 secretion systems, and retention at the cell surface. Published work has shown that retention of the adhesins occurs via a post-translational mechanism involving the cyclic-di-GMP receptor LapD and the protease LapG. However, little is known about the underlying mechanisms that regulate the level of these adhesins. Here, we demonstrate that the master regulator FleQ modulates biofilm formation by both transcriptionally and post-transcriptionally regulating LapA and MapA. We find that a Δ mutant has a biofilm formation defect compared to the wild-type (WT) strain, which is attributed in part to a decrease in LapA and MapA abundance in the cell, despite the Δ mutant having increased levels of and transcripts compared to the WT strain. Through transposon mutagenesis and subsequent genetic analysis, we found that overstimulation of the Gac/Rsm pathway partially rescues biofilm formation in the Δ mutant background. Collectively, these findings provide evidence that FleQ regulates biofilm formation by both transcriptionally regulating the expression of the genes and post-transcriptionally regulating the abundance of LapA and MapA, and that activation of the Gac/Rsm pathway can post-transcriptionally enhance biofilm formation by . IMPORTANCE Biofilm formation is a highly coordinated process that bacteria undergo to colonize a variety of surfaces. For , biofilm formation requires the production and localization of repeats-in-toxin adhesins to the cell surface. To date, little is known about the underlying mechanisms that regulate biofilm formation by . Here, we identify FleQ as a key regulator of biofilm formation that modulates both gene expression and abundance of LapA and MapA through both a transcriptional and post-transcriptional mechanism. We provide further evidence implicating activation of the Gac/Rsm system in FleQ-dependent regulation of biofilm formation. Together, our findings uncover evidence for a dual mechanism of transcriptional and post-transcriptional regulation of the LapA and MapA adhesins.
Topics: Pseudomonas fluorescens; Biofilms; Adhesins, Bacterial; Carrier Proteins; Bacterial Proteins; Gene Expression Regulation, Bacterial; Cyclic GMP
PubMed: 37655913
DOI: 10.1128/jb.00152-23 -
Food Research International (Ottawa,... Nov 2023This study established microbial growth models for fresh-cut cucumber packaged with different O transmission rate (OTR) films. Biaxially oriented polyamide/low-density...
This study established microbial growth models for fresh-cut cucumber packaged with different O transmission rate (OTR) films. Biaxially oriented polyamide/low-density polyethylene (BOPA/LDPE) film (Ⅰ: OTR5, Ⅳ: OTR48) and polyethylene (PE) film (Ⅱ: OTR2058, Ⅲ: OTR3875) were used to construct a passive modified atmosphere packaging (MAP). Mathematic models have been established to account for dynamic variations in the O/CO concentration and their impacts on Pseudomonas fluorescens growth. The coupling models included: 1) respiration models of cucumber and P. fluorescens based on Michaëlis-Menten equation, 2) coupling gas exchange models based on Fick's law that contained models of P. fluorescens growth and respiration, 3) coupling microbial growth models contained respiration and gas exchange models. Coupling model with Baranyi function successfully fitted variations of O/CO concentration and P. fluorescens growth in the two packaging. In addition, quality properties of packed fresh-cut cucumber were determined. The film Ⅳ (OTR48) as a high barrier film showed the highest inhibition of P. fluorescens growth, adequately retained its colour, firmness and total soluble solid (TSS) concentration in contrast to the PE films packaging. The constructed coupling models can be utilized for assessing the shelf life and microbial growth of fresh-cut vegetables with spoilage dominated by pseudomonads.
Topics: Cucumis sativus; Food Packaging; Food Preservation; Pseudomonas fluorescens; Carbon Dioxide; Food Microbiology; Atmosphere
PubMed: 37803617
DOI: 10.1016/j.foodres.2023.113306 -
Physiologia Plantarum 2023Salt stress is an alarming abiotic stress that reduces mustard growth and yield. To attenuate salt toxicity effects, plant growth-promoting rhizobacteria (PGPR) offers a...
Salt stress is an alarming abiotic stress that reduces mustard growth and yield. To attenuate salt toxicity effects, plant growth-promoting rhizobacteria (PGPR) offers a sustainable approach. Among the various PGPR, Pseudomonas fluorescens (P. fluorescens NAIMCC-B-00340) was chosen for its salt tolerance (at 100 mM NaCl) and for exhibiting various growth-promoting activities. Notably, P. fluorescens can produce auxin, which plays a role in melatonin (MT) synthesis. Melatonin is a pleiotropic molecule that acts as an antioxidant to scavenge reactive oxygen species (ROS), resulting in stress reduction. Owing to the individual role of PGPR and MT in salt tolerance, and their casual nexus, their domino effect was investigated in Indian mustard under salt stress. The synergistic action of P. fluorescens and MT under salt stress conditions was found to enhance the activity of antioxidative enzymes and proline content as well as promote the production of secondary metabolites. This led to reduced oxidative stress following effective ROS scavenging, maintained photosynthesis, and improved growth. In mustard plants treated with MT and P. fluorescens under salt stress, eight flavonoids showed significant increase. Kaempferol and cyanidin showed the highest concentrations and are reported to act as antioxidants with protective functions under stress. Thus, we can anticipate that strategies involved in their enhancement could provide a better adaptive solution to salt toxicity in mustard plants. In conclusion, the combination of P. fluorescens and MT affected antioxidant metabolism and flavonoid profile that could be used to mitigate salt-induced stress and bolster plant resilience.
Topics: Antioxidants; Melatonin; Mustard Plant; Pseudomonas fluorescens; Reactive Oxygen Species; Flavonoids
PubMed: 38148187
DOI: 10.1111/ppl.14092 -
Microorganisms Dec 2023Coal mining has caused significant soil nitrogen loss in mining areas, limiting reclamation and reuse in agriculture. This article studies the effects of organic...
Coal mining has caused significant soil nitrogen loss in mining areas, limiting reclamation and reuse in agriculture. This article studies the effects of organic fertilizer, inorganic fertilizer, and the combined application of with the ability of nitrogen fixation on soil nitrogen accumulation and composition in the reclamation area of the Tunlan Coal Mine from 2016 to 2022 under the conditions of equal nitrogen application, providing a scientific basis for microbial fertilization and the rapid increase in nitrogen content in the reclaimed soil of mining areas. The results showed that as the reclamation time increased, the nitrogen content and the composition and structure of the soil treated with fertilization rapidly evolved toward normal farmland soil. The soil nitrogen content increased most rapidly in the presence of added + organic fertilizer (MB). Compared to other treatments (inorganic fertilizer (CF), organic fertilizer (M), and + inorganic fertilizer (CFB)), MB increased total nitrogen (TN) to normal farmland soil levels 1-3 years earlier. The comprehensive scores of MB and CFB on the two principal components increased by 1.58 and 0.79 compared to those of M and CF treatments, respectively. This indicates that the combination of and organic fertilizer improves soil nitrogen accumulation more effectively than the combination of and inorganic fertilizer. In addition, the application of increases the content of unknown nitrogen (UN) in acid-hydrolysable nitrogen (AHN) and decreases the content of amino acid nitrogen (AAN) and ammonia nitrogen (AN). However, there was no significant effect on the content of ammonium nitrogen (NH-N) and nitrate nitrogen (NO-N) in soil-mineralized nitrogen (SMN). When combined with inorganic fertilizer, the contribution of SMN to TN increased by 14.78%, while when combined with organic fertilizer, the contribution of AHN to TN increased by 44.77%. In summary, the use of is beneficial for nitrogen recovery in the reclaimed soil of coal-mining areas. The optimal fertilization method under the experimental conditions is the combination of and organic fertilizer.
PubMed: 38276177
DOI: 10.3390/microorganisms12010009 -
Brazilian Journal of Microbiology :... Dec 2023Pseudomonas fluorescens group strains can lead to spoilage of milk as well as loss of quality in dairy products through their heat-resistant enzymes. Phages are...
Pseudomonas fluorescens group strains can lead to spoilage of milk as well as loss of quality in dairy products through their heat-resistant enzymes. Phages are important alternatives for combating spoilage bacteria in food industry and used successfully in many applications. The aim of this study was the isolation and characterization of phages and to assess the efficiency of a phage cocktail in whole and skimmed milk. For this purpose, phages effective against Pseudomonas fluorescens (L23.2), Pseudomonas tolaasii (P22.1), and Pseudomonas rhodesiae (A11.1) were isolated. Their host range was found to be highly specific, and the transmission electron micrographs indicates that they belonged to Tectiviridae family. Their genome sizes were found to be vary between 38.3 and 53.5 kb. The latent periods and burst sizes were determined as 15, 10, 15 min and 91, 20, 80 PFU/infected cell for L23.2, P22.1, and A11.1, respectively. All three phages were found to be sensitive to low pH and high temperature. The effect of the phage cocktail was monitored in milk with different fat contents during storage at 4 °C for 5 days. As a result, bacterial reductions up to 4.09 and 5.29 log-units were observed for the whole and skimmed milk, respectively. Thus, the efficacy of a phage cocktail against a bacterial mixture of different P. fluorescens strains was tested in milk samples with different fat contents in accordance with real-life scenarios for the first time.
Topics: Animals; Milk; Bacteriophages; Pseudomonas fluorescens; Food Microbiology; Hot Temperature
PubMed: 37914971
DOI: 10.1007/s42770-023-01164-2