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Journal of Agricultural and Food... Nov 2021Preharvest application of biocontrol agents is a promising strategy for promoting biosynthesis and accumulation of functional ingredients in fruit crops. In this study,...
Preharvest application of biocontrol agents is a promising strategy for promoting biosynthesis and accumulation of functional ingredients in fruit crops. In this study, we sought to evaluate the potential of ZX in stimulating the primary and secondary metabolism of citrus fruit peel. Pretreatment with ZX was found to significantly affect the concentrations and profiles of both primary and secondary metabolites. More importantly, using ZX suspension to increase inoculation numbers during fruit development typically elicited stronger stimulus effects, and multiple applications of ZX significantly improved the biosynthesis process of beneficial compounds, resulting in their abundant accumulation in the peel. In fruit pretreated four times with ZX, hesperidin, sinensetin, nobiletin, synephrine, and pectin were increased by approximately 26.0, 31.3, 44.8, 19.7, and 23.1%, respectively, compared to the untreated control. Collectively, these results indicated that, as a biostimulant, preharvest application of ZX is an effective, affordable, ecological, and ecofriendly alternative agricultural technique for exploiting citrus crops. This approach is also promising for increasing the value of citrus fruit peel (currently regarded primarily as processing waste), thereby allowing industrial agricultural practices to move one step closer toward a circular economy.
Topics: Citrus; Fruit; Hesperidin; Pseudomonas fluorescens; Secondary Metabolism
PubMed: 34751564
DOI: 10.1021/acs.jafc.1c05709 -
Journal of Evolutionary Biology Feb 2017When competing for space and resources, bacteria produce toxins known as bacteriocins to gain an advantage over competitors. Recent studies in the laboratory have...
When competing for space and resources, bacteria produce toxins known as bacteriocins to gain an advantage over competitors. Recent studies in the laboratory have confirmed theoretical predictions that bacteriocin production can determine coexistence, by eradicating sensitive competitors or driving the emergence of resistant genotypes. However, there is currently limited evidence that bacteriocin-mediated competition influences the coexistence and distribution of genotypes in natural environments, and what factors drive interactions towards inhibition remain unclear. Using natural soil populations of Pseudomonas fluorescens, we assessed the ability of the isolates to inhibit one another with respect to spatial proximity in the field, genetic similarity and niche overlap. The majority of isolates were found to produce bacteriocins; however, widespread resistance between coexisting isolates meant relatively few interactions resulted in inhibition. When inhibition did occur, it occurred more frequently between ecologically similar isolates. However, in contrast with results from other natural populations, we found no relationship between the frequency of inhibition and the genetic similarity of competitors. Our results suggest that bacteriocin production plays an important role in mediating competition over resources in natural settings and, by selecting for isolates resistant to local bacteriocin production, can influence the assembly of natural populations of P. fluorescens.
Topics: Bacteriocins; Genetic Variation; Population Dynamics; Pseudomonas fluorescens; Soil Microbiology
PubMed: 28000957
DOI: 10.1111/jeb.13010 -
Ecotoxicology and Environmental Safety Jan 2019Dimethyl phthalate (DMP) is a ubiquitous pollutant that is very harmful to organisms due to its mutagenicity, teratogenicity and carcinogenicity. Pseudomonas fluorescens...
Dimethyl phthalate (DMP) is a ubiquitous pollutant that is very harmful to organisms due to its mutagenicity, teratogenicity and carcinogenicity. Pseudomonas fluorescens (P. fluorescens) is one of the most important bacteria in the environment. In this study, the response of P. fluorescens to DMP was investigated. It was found that DMP greatly inhibited the growth and glucose utilization of P. fluorescens when the concentration of DMP was ranged from 20 to 40 mg/l. The surface hydrophobicity and membrane permeability of P. fluorescens were also increased by DMP. DMP could lead to the deformations of cell membrane and the mis-opening of membrane channels. RNA-Seq and RT-qPCR results showed that the expression of some genes in P. fluorescens were altered, including the genes involved in energy metabolism, ATP-binding cassette (ABC) transporting and two-component systems. Additionally, the productions of lactic acid and pyruvic acid were reduced and the activity of hexokinase was inhibited in P. fluorescens by DMP. Clearly, the results suggested that DMP contamination could alter the biological function of P. fluorescens in the environment.
Topics: ATP-Binding Cassette Transporters; Dose-Response Relationship, Drug; Gene Expression Regulation, Bacterial; Hydrophobic and Hydrophilic Interactions; Mutagens; Phthalic Acids; Pseudomonas fluorescens; Sequence Analysis, RNA; Transcriptome
PubMed: 30292974
DOI: 10.1016/j.ecoenv.2018.09.078 -
Food Microbiology Oct 2020Biofilm formation is a frequent source of contamination of food products, which results in significant economic losses through microbial spoilage and poses serious...
Biofilm formation is a frequent source of contamination of food products, which results in significant economic losses through microbial spoilage and poses serious health concerns. Little is known about the fate of Staphylococcus aureus in the dual-species biofilms with Pseudomonas fluorescens an important spoiler commonly found in aquatic products. This study evaluates the interactions between mono- or dual-species biofilms formed by P. fluorescens and S. aureus, as well as the sensitivity of the two tested strains to carvacrol. The biofilm cell population, expolysaccharide production, biofilm structures of P. fluorescens as mono- and dual-species with S. aureus at ratios of 1:1 and 1:0.01 were investigated with different concentrations of carvacrol (0, 0.4, 0.8 and 1.6 mM) in fish juice at 30 °C. The results show that the biofilm cell population of S. aureus in the dual-species was significantly lower (p < 0.05) than that in the mono-species, compared to no difference for P. fluorescens. In the co-culture the dominance of P. fluorescens inhibited the growing population of S. aureus in both planktonic and biofilm cells, however, two strains were stimulated to produce the large expolysaccharides and coaggregation, forming the complex spatial multibiofilm structures. The large increase in the dual-species biofilms was positively correlated with high quorum sensing autoinductor-2 (AI-2), and exogenous 4,5-dihydroxy-2,3-pentanedione (the AI-2 precursor, DPD), rather than C-HSL, greatly stimulated the dual-species biofilm formation. In addition, carvacrol significantly reduced the tested biofilms and expolysaccharide secretion without affecting cell viability in a concentration-dependent manner, especially for S. aureus. Furthermore, the two strains as the dual-species biofilms exhibited lower sensitivity to carvacrol than the mono-culture, regardless of the level of inoculum of S. aureus, which was consistent with the decrease of AI-2 activity. The present study highlights that the interactions between P. fluorescens and S. aureus in dual-species biofilms promoted the large production of expolysaccharides and complex biofilm structures modulated by AI-2 signal, which results in the community-level resistance to carvacrol.
Topics: Animals; Biofilms; Cymenes; Drug Resistance, Bacterial; Extracellular Polymeric Substance Matrix; Fishes; Homoserine; Lactones; Microbial Interactions; Pseudomonas fluorescens; Quorum Sensing; Seafood; Staphylococcus aureus
PubMed: 32539951
DOI: 10.1016/j.fm.2020.103506 -
Letters in Applied Microbiology Apr 2023This study aimed to examine the inhibition of chlorogenic acid-grafted chitosan (CS-g-CA) on Pseudomonas fluorescens (P. fluorescens) and its biofilm. The minimum...
This study aimed to examine the inhibition of chlorogenic acid-grafted chitosan (CS-g-CA) on Pseudomonas fluorescens (P. fluorescens) and its biofilm. The minimum inhibitory concentration (MIC) of CS-g-CA against P. fluorescens was 1.25 mg/mL. Alkaline phosphatase (AKPase) leakage assay and scanning electron microscopy (SEM) observation showed that CS-g-CA causes structural damage to cell walls and membranes, resulting in the loss of function. In addition, CS-g-CA was able to disrupt the antioxidant system of P. fluorescens, interfere with energy metabolism, and interact with genomic DNA, affecting the normal physiological function of bacteria. It was also found that CS-g-CA inhibited the flagellar motility of P. fluorescens, which may be responsible for the inhibition of its biofilm formation. CS-g-CA at 2MIC was able to remove 71.64% of the mature biofilm and reduce the production of extracellular polysaccharides (EPS) by 60.72%. This was further confirmed by confocal laser scanning microscopy (CLSM), which showed a significant reduction in the amount of biofilm. In summary, CS-g-CA has strong antibacterial and anti-biofilm activities against P. fluorescens, and it can be applied as a potential seafood bacteriostatic agent.
Topics: Chitosan; Pseudomonas fluorescens; Chlorogenic Acid; Biofilms; Anti-Bacterial Agents; Seafood
PubMed: 37081770
DOI: 10.1093/lambio/ovad050 -
International Journal of Molecular... Dec 2022SBW25 is a model soil- and plant-associated bacterium capable of forming a variety of air-liquid interface biofilms in experimental microcosms and on plant surfaces....
SBW25 is a model soil- and plant-associated bacterium capable of forming a variety of air-liquid interface biofilms in experimental microcosms and on plant surfaces. Previous investigations have shown that cellulose is the primary structural matrix component in the robust and well-attached Wrinkly Spreader biofilm, as well as in the fragile Viscous Mass biofilm. Here, we demonstrate that both biofilms include extracellular DNA (eDNA) which can be visualized using confocal laser scanning microscopy (CLSM), quantified by absorbance measurements, and degraded by DNase I treatment. This eDNA plays an important role in cell attachment and biofilm development. However, exogenous high-molecular-weight DNA appears to decrease the strength and attachment levels of mature Wrinkly Spreader biofilms, whereas low-molecular-weight DNA appears to have little effect. Further investigation with CLSM using an amyloid-specific fluorophore suggests that the Wrinkly Spreader biofilm might also include Fap fibers, which might be involved in attachment and contribute to biofilm strength. The robust nature of the Wrinkly Spreader biofilm also allowed us, using MALDI-TOF mass spectrometry, to identify matrix-associated proteins unable to diffuse out of the structure, as well as membrane vesicles which had a different protein profile compared to the matrix-associated proteins. CLSM and DNase I treatment suggest that some vesicles were also associated with eDNA. These findings add to our understanding of the matrix components in this model pseudomonad, and, as found in other biofilms, biofilm-specific products and material from lysed cells contribute to these structures through a range of complex interactions.
Topics: Biofilms; Deoxyribonuclease I; DNA; DNA, Bacterial; Pseudomonas fluorescens; Amyloid
PubMed: 36499433
DOI: 10.3390/ijms232315096 -
Microbiology (Reading, England) Jul 2019In natural habitats, bacterial species often coexist in biofilms. They interact in synergetic or antagonistic ways and their interactions can influence the biofilm...
In natural habitats, bacterial species often coexist in biofilms. They interact in synergetic or antagonistic ways and their interactions can influence the biofilm development and properties. Still, very little is known about how the coexistence of multiple organisms impact the multispecies biofilm properties. In this study, we examined the behaviour of a dual-species biofilm at the air-liquid interface composed by two environmental bacteria: Bacillus licheniformis and a phenazine mutant of Pseudomonas fluorescens. Study of the planktonic and biofilm growths for each species revealed that P. fluorescens grew faster than B. licheniformis and no bactericidal effect from P. fluorescens was detected, suggesting that the growth kinetics could be the main factor in the dual-species biofilm composition. To validate this hypothesis, the single- and dual-species biofilm were characterized by biomass quantification, microscopy and rheology. Bacterial counts and microscale architecture analysis showed that both bacterial populations coexist in the mature pellicle, with a dominance of P. fluorescens. Real-time measurement of the dual-species biofilms' viscoelastic (i.e. mechanical) properties using interfacial rheology confirmed that P. fluorescens was the main contributor of the biofilm properties. Evaluation of the dual-species pellicle viscoelasticity at longer time revealed that the biofilm, after reaching a first equilibrium, created a stronger and more cohesive network. Interfacial rheology proves to be a unique quantitative technique, which combined with microscale imaging, contributes to the understanding of the time-dependent properties within a polymicrobial community at various stages of biofilm development. This work demonstrates the importance of growth kinetics in the bacteria competition for the interface in a model dual-species biofilm.
Topics: Bacillus licheniformis; Biofilms; Kinetics; Pseudomonas fluorescens; Staining and Labeling
PubMed: 31145677
DOI: 10.1099/mic.0.000819 -
Applied and Environmental Microbiology Sep 2021Within soil, bacteria are found in multispecies communities, where interactions can lead to emergent community properties. Studying bacteria in a social context is...
Exploration of Social Spreading Reveals That This Behavior Is Prevalent among and Pseudomonas fluorescens Isolates and That There Are Variations in the Induction of the Phenotype.
Within soil, bacteria are found in multispecies communities, where interactions can lead to emergent community properties. Studying bacteria in a social context is critical for investigating community-level functions. We previously showed that cocultured Pseudomonas fluorescens Pf0-1 and sp. V48 engage in interspecies social spreading (ISS) on a hard agar surface, a behavior which required close contact and depended on the nutritional environment. Here, we investigate whether social spreading is widespread among P. fluorescens and isolates and whether the requirements for interaction vary. We find that this phenotype is not restricted to the interaction between P. fluorescens Pf0-1 and sp. V48 but is a prevalent behavior found in one clade in the P. fluorescens group and two clades in the genus. We show that the interaction with certain isolates occurred without close contact, indicating induction of spreading by a putative diffusible signal. As with ISS by Pf0-1+V48, the motility of interacting pairs is influenced by the environment, with no spreading behaviors (or induction of motility) observed under high nutrient conditions. While Pf0-1+V48 require low nutrient but high NaCl conditions, in the broader range of interacting pairs, the high salt influence was variable. The prevalence of motility phenotypes observed here and found within the literature indicates that community-induced locomotion in general, and social spreading in particular, is likely important within the environment. It is crucial that we continue to study microbial interactions and their emergent properties to gain a fuller understanding of the functions of microbial communities. Interspecies social spreading (ISS) is an emergent behavior observed when Pseudomonas fluorescens Pf0-1 and sp. V48 interact, during which both species move together across a surface. Importantly, this environment does not permit the movement of either individual species. This group behavior suggests that communities of microbes can function in ways not predictable by knowledge of the individual members. Here, we have asked whether ISS is widespread and thus potentially of importance in soil microbial communities. The significance of this research is the demonstration that surface spreading behaviors are not unique to the Pf0-1-V48 interaction but rather is a more widespread phenomenon observed among members of distinct clades of both P. fluorescens and isolates. Furthermore, we identify differences in mechanisms of signaling and nutritional requirements for ISS. Emergent traits resulting from bacterial interactions are widespread, and their characterization is necessary for a complete understanding of microbial community function.
Topics: Microbial Interactions; Pedobacter; Phenotype; Phylogeny; Pseudomonas fluorescens; RNA, Ribosomal, 16S; Soil Microbiology
PubMed: 34288708
DOI: 10.1128/AEM.01344-21 -
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 -
Applied and Environmental Microbiology Jul 2022Pseudomonas fluorescens 2P24 is a beneficial plant root-associated microorganism capable of suppressing several soilborne plant diseases. The capacity of P. fluorescens...
Pseudomonas fluorescens 2P24 is a beneficial plant root-associated microorganism capable of suppressing several soilborne plant diseases. The capacity of P. fluorescens to aggressively colonize the rhizosphere is an important requirement for its biocontrol trait. We previously found that the PcoI/PcoR quorum-sensing system (QS) is involved in regulating the rhizosphere colonization of P. fluorescens. Here, we revealed a sophisticated regulatory network that connects PcoR, RsaL, and MvaT proteins to fine-tune the PcoI/PcoR QS system. Our data showed that PcoR could directly bind to the promoter region of thereby inducing the PcoI/PcoR QS system, whereas RsaL binds simultaneously with PcoR to the promoter region of and represses the PcoR-dependent activation of gene. In addition, RsaL indirectly downregulates the expression of . Furthermore, we showed that disruption of enhanced the expression of , , and , whereas MvaT controls the PcoI/PcoR QS in a RsaL-independent manner. Overall, this study elucidates that PcoR, RsaL, and MvaT regulate the PcoI/PcoR QS through a multi-tiered regulatory mechanism and that PcoR is necessary in the RsaL- and MvaT-mediated repression on the expression of . The PcoI/PcoR quorum-sensing system of Pseudomonas fluorescens 2P24 is important for its effective colonization in the plant rhizosphere. Many regulatory elements appear to directly or indirectly influence the QS system. Here, we found a complex regulatory network employing transcriptional factors PcoR, RsaL, and MvaT to influence the expression of the PcoI/PcoR QS in P. fluorescens 2P24. Our results indicate that PcoR and RsaL directly bind to the promoter region of and then positively and negatively regulate the expression of , respectively. Furthermore, the H-NS family protein MvaT negatively controls the PcoI/PcoR QS in a RsaL-independent manner. Taken together, our data provide new insights into the interplays between different regulatory elements that fine-tune the QS system of P. fluorescens.
Topics: Bacterial Proteins; Gene Expression Regulation, Bacterial; Pseudomonas aeruginosa; Pseudomonas fluorescens; Quorum Sensing; Transcription Factors
PubMed: 35695573
DOI: 10.1128/aem.00625-22