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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 -
Microorganisms Jul 2022Microbial bio-products are becoming an appealing and viable alternative to chemical pesticides for effective management of crop diseases. These bio-products are known to...
Microbial bio-products are becoming an appealing and viable alternative to chemical pesticides for effective management of crop diseases. These bio-products are known to have potential to minimize agrochemical applications without losing crop yield and also restore soil fertility and productivity. In this study, the inhibitory efficacy of 2,4-diacetylphloroglucinol (DAPG) produced by VSMKU3054 against was assessed. Biochemical and functional characterization study revealed that produced hydrogen cyanide (HCN), siderophore, indole acetic acid (IAA) and hydrolytic enzymes such as amylase, protease, cellulase and chitinase, and had the ability to solubilize phosphate. The presence of the key antimicrobial encoding gene in the biosynthesis of 2,4-diacetylphloroglucinol (DAPG) was identified by PCR. The maximum growth and antimicrobial activity of was observed in king's B medium at pH 7, 37 °C and 36 h of growth. Glucose and tryptone were found to be the most suitable carbon and nitrogen sources, respectively. DAPG was separated by silica column chromatography and identified by various methods such as UV-Vis, FT-IR, GC-MS and NMR spectroscopy. When cells were exposed to DAPG at 90 µg/mL, the cell viability was decreased, reactive oxygen species (ROS) were increased and chromosomal DNA was damaged. Application of and DAPG significantly reduced the bacterial wilt incidence. In addition, was also found effective in promoting the growth of tomato seedlings. It is concluded that the indigenous isolate VSMKU3054 could be used as a suitable biocontrol agent against bacterial wilt disease of tomato.
PubMed: 35893565
DOI: 10.3390/microorganisms10081508 -
Bactericidal Efficacy and Mechanisms of Non-Electrolytic Slightly Acidic Hypochlorous Water on and .Foods (Basel, Switzerland) Oct 2023Chilled pork is frequently contaminated with and . In this study, the bactericidal efficacy and mechanisms of non-electrolytic slightly acidic hypochlorous water...
Chilled pork is frequently contaminated with and . In this study, the bactericidal efficacy and mechanisms of non-electrolytic slightly acidic hypochlorous water (NE-SAHW) against two strains of these two species were evaluated. The results showed that the antibacterial efficacy of NE-SAHW was positively correlated with the concentration level of NE-SAHW and negatively correlated with the initial populations of the strains. The strains of small populations were completely inhibited when provided with each level of NE-SAHW. The killed cells of were 0.94, 1.39, 4.02, and 5.60 log10 CFU/mL, respectively, and of they were 1.21, 1.52, 4.14, and 5.74 log10 CFU/mL, respectively, when the initial populations of the strains were at high levels (about 7 log10 CFU/mL). Both strains were completely killed within 12 s with the available chlorine concentration (ACC) of 50 mg/L of NE-SAHW. Morphological changes in both cells were observed by using a Scanning Electron Microscope (SEM) and it was discovered that the cell membranes were damaged, which led to the leakage of the intracellular substances, including K+, nucleic acid, and protein. In terms of the Fourier Transform Infrared Spectroscopy (FTIR) results, NE-SAHW destroyed the structures of membrane proteins and cell structure proteins, and influenced the composition of polysaccharides. The bacteria were definitely dead after treatment by NE-SAHW compared to the control according to the results of flow cytometry. These results demonstrated the potential bactericidal property of NE-SAHW when applied to the meat and other food sterilization industries.
PubMed: 37959099
DOI: 10.3390/foods12213980 -
The Science of the Total Environment Jul 2020Plant growth-promoting bacteria (PGPB) can promote photosynthesis and biomass production of hyperaccumulators, achieving enhanced phytoremediation efficiency of cadmium...
Plant growth-promoting bacteria (PGPB) can promote photosynthesis and biomass production of hyperaccumulators, achieving enhanced phytoremediation efficiency of cadmium (Cd). A better understanding of the mechanisms controlling photosynthesis of hyperaccumulating plants by PGPB is necessary for developing strategies that promote the practical phytoextraction of Cd-polluted soils. In this study, chlorophyll fluorescence, gas exchange, and transcriptome sequencing were conducted to evaluate the physiological and transcriptional changes on photosynthesis and carbon fixation in hyperaccumulator Sedum alfredii after inoculation with PGPB Pseudomonas fluorescens. The results showed that bacterial inoculation significantly enhanced maximum quantum yield of PS II (Fv/Fm), effective quantum yield of PS II (ΦPSII), photochemical quenching (qP) and chlorophyll concentration, while reduced non-photochemical quenching (NPQ) of S. alfredii. Further, inoculation resulted in an increased net photosynthetic rates (Pn), intercellular CO concentration (Ci), transpiration rate (Tr) and stomatal conductance (Gs) of the studied plant. At the transcriptional level, 70 photosynthetic genes and 42 C4-pathway carbon fixation related genes were significantly up-regulated in response to inoculation, which could be the reason for enhanced photosynthesis and dry biomass. To sum up, this P. fluorescens strain can simultaneously promote growth and Cd uptake of S. alfredii, which can be a promising bacterial agent applied to Cd phytoremediation practices.
Topics: Biodegradation, Environmental; Cadmium; Carbon Cycle; Chlorophyll; Photosynthesis; Plant Roots; Pseudomonas fluorescens; Sedum
PubMed: 32305763
DOI: 10.1016/j.scitotenv.2020.138554 -
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 -
Microbiological Research Sep 2021Pseudomonas fluorescens ATCC13525 is an important growth-promoting rhizobacteria (PGPR) and plant disease biocontrol bacterium. However, due to poor stress resistance,...
Pseudomonas fluorescens ATCC13525 is an important growth-promoting rhizobacteria (PGPR) and plant disease biocontrol bacterium. However, due to poor stress resistance, it is prone to be inactivated by preparation, drying and storage. In this study, we investigated the effects of different stress preadaptation methods (2.0∼3.0 wt% NaCl, 0.01∼0.20 wt% HO, and 35∼44 °C) and two stress adaptation genes (rpoS, and hfq) on the stress resistance of P. fluorescens ATCC13525 (PF-WT). After stress preadaptation with low stress of 3.0 wt% NaCl, 0.05 wt% HO, and 41 °C for 30 min, the tolerance of PF-WT toward high lethal stress environments (20.0 wt% NaCl, 1.00 wt% HO, and 47 °C) were significantly improved. Moreover, knockout of rpoS and hfq genes resulted in slower culture growth than PF-WT under the sublethal stress culture conditions (5.0 wt% NaCl, 0.08 wt% HO, and 35 °C), whereas rpoS and hfq overexpressed strains (PF-pBBR2-rpoS and PF-pBBR2-hfq) obviously grew better than the control strain PF-pBBR2. Further, we prepared biocontrol agents (BACs) of different strains after different stress preadaptation treatments. Compared to PF-WT without stress preadaptation, preadaptation by 0.05 wt% HO for 30 min resulted in 5.65 times higher survival rate, while treatment with 3.0 wt% NaCl for 30 min of PF-pBBR2-rpoS led to 5.60 times higher survival rate. This finding provides the simple and effective protection methods for P. fluorescens ATCC13525 BACs preparation by stress preadaptation and overexpression of stress adaptation genes.
Topics: Adaptation, Physiological; Bacterial Proteins; Biological Control Agents; Host Factor 1 Protein; Hydrogen Peroxide; Pseudomonas fluorescens; Sigma Factor; Stress, Physiological
PubMed: 34144508
DOI: 10.1016/j.micres.2021.126804 -
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 -
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 -
Meat Science Jun 2022Hyperspectral imaging (HSI) is a promising technique that can replace the time-consuming and destructive plate count method. In this study, growth models of Pseudomonas...
Hyperspectral imaging (HSI) is a promising technique that can replace the time-consuming and destructive plate count method. In this study, growth models of Pseudomonas fluorescens (P. fluorescens) in pork using the plate count method and HSI were established. Hyperspectral information extracted by three different methods was used for the growth simulation of P. fluorescens. The Baranyi model in combination with the Ratkowsky square-root model (BRSR model) and the Huang model in combination with the Ratkowsky square-root model (HRSR model) for P. fluorescens in pork were directly constructed using a one-step method. Results showed that the correlation coefficients between the growth models established using HSI and the plate count method were high, ranging from 0.952-0.999. The adjusted coefficient of determination (R) of simulation models reached 0.974, and the growth parameters obtained were consistent with those obtained using the plate count method. This study demonstrated that HSI may be potentially used as a new predictive microbial modeling technique in the future.
Topics: Animals; Food Microbiology; Hyperspectral Imaging; Pork Meat; Pseudomonas fluorescens; Red Meat; Swine
PubMed: 35228138
DOI: 10.1016/j.meatsci.2022.108767