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Journal of Bacteriology Oct 2016Microbial adaptation is conspicuous in essentially every environment, but the mechanisms of adaptive evolution are poorly understood. Studying evolution in the... (Review)
Review
Microbial adaptation is conspicuous in essentially every environment, but the mechanisms of adaptive evolution are poorly understood. Studying evolution in the laboratory under controlled conditions can be a tractable approach, particularly when new, discernible phenotypes evolve rapidly. This is especially the case in the spatially structured environments of biofilms, which promote the occurrence and stability of new, heritable phenotypes. Further, diversity in biofilms can give rise to nascent social interactions among coexisting mutants and enable the study of the emerging field of sociomicrobiology. Here, we review findings from laboratory evolution experiments with either Pseudomonas fluorescens or Burkholderia cenocepacia in spatially structured environments that promote biofilm formation. In both systems, ecotypes with overlapping niches evolve and produce competitive or facilitative interactions that lead to novel community attributes, demonstrating the parallelism of adaptive processes captured in the lab.
Topics: Biofilms; Burkholderia cenocepacia; Directed Molecular Evolution; Pseudomonas fluorescens
PubMed: 27044625
DOI: 10.1128/JB.01018-15 -
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 -
BMC Microbiology Jul 2020Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne...
BACKGROUND
Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne plant diseases. The biosynthesis of 2,4-DAPG is strictly regulated by the RsmA family proteins RsmA and RsmE. However, mutation of both of rsmA and rsmE genes results in reduced bacterial growth.
RESULTS
In this study, we showed that overproduction of 2,4-DAPG in the rsmA rsmE double mutant influenced the growth of strain 2P24. This delay of growth could be partially reversal when the phlD gene was deleted or overexpression of the phlG gene encoding the 2,4-DAPG hydrolase in the rsmA rsmE double mutant. RNA-seq analysis of the rsmA rsmE double mutant revealed that a substantial portion of the P. fluorescens genome was regulated by RsmA family proteins. These genes are involved in the regulation of 2,4-DAPG production, cell motility, carbon metabolism, and type six secretion system.
CONCLUSIONS
These results suggest that RsmA and RsmE are the important regulators of genes involved in the plant-associated strain 2P24 ecologic fitness and operate a sophisticated mechanism for fine-tuning the concentration of 2,4-DAPG in the cells.
Topics: Bacterial Proteins; Carbon; Gene Deletion; Gene Expression Regulation, Bacterial; Methyltransferases; Mutation; Phloroglucinol; Pseudomonas fluorescens; RNA-Binding Proteins; Sequence Analysis, RNA
PubMed: 32615927
DOI: 10.1186/s12866-020-01880-x -
Food Microbiology Feb 2022In this study, P. fluorescens-infecting phages were isolated, characterized, and evaluated to their potential to control the bacterial counts and, consequently, the...
In this study, P. fluorescens-infecting phages were isolated, characterized, and evaluated to their potential to control the bacterial counts and, consequently, the proteolytic spoilage of raw milk during cold storage. The UFJF_PfDIW6 and UFJF_PfSW6 phages showed titers of 9.7 and 7.6 log PFU/ml; latent period of 115 and 25 min, and burst size of 145 and 25 PFU/infected cell, respectively. They also were highly specific to the host bacterium, morphologically classified as the Podoviridae family, stable at pH 5 to 11 and were not inactivated at 63 °C or 72 °C for 30 min. These phages found to be effective against P. fluorescens, reducing bacterial count throughout the entire exponential growth phase in broth formulated with milk at both 4 °C and 10 °C. This effect on bacteria growth led to inhibition by at least 2 days in proteases production, delaying the degradation of milk proteins. When applied together in raw milk stored at 4 °C, they reduced the total bacteria, psychrotrophic, and Pseudomonas by 3 log CFU/ml. This study's findings indicate that these phages have a great potential to prevent the growth of Pseudomonas and, consequently, to retard proteolytic spoilage of raw milk during chilled storage.
Topics: Animals; Bacteriophages; Cold Temperature; Food Contamination; Food Microbiology; Food Storage; Milk; Peptide Hydrolases; Pseudomonas fluorescens
PubMed: 34579852
DOI: 10.1016/j.fm.2021.103892 -
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 -
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 -
The Journal of General and Applied... Sep 2017The tea mosquito bug (TMB), Helopeltis spp. (Hemiptera: Miridae) is an insidious pest that poses a significant economical threat to tea plantations. Pseudomonas cultures...
The tea mosquito bug (TMB), Helopeltis spp. (Hemiptera: Miridae) is an insidious pest that poses a significant economical threat to tea plantations. Pseudomonas cultures are being used extensively for pest management which, however, resulting in a low mortality rate of insects and which has prompted us to search for a new microbial metabolite for TMB control. A chitinase purified from P. fluorescens and partially characterized by our group showed insecticidal activity against TMB. The mode of action behind chitinase toxicity is the enzymatic hydrolysis of chitin, which is a common constituent of the insect exoskeleton and gut lining of the peritrophic membrane. A chitinase-secreting strain MP-13 was characterized based on 16S rRNA sequencing and validated as Pseudomonas fluorescens. In the present study, purified chitinase (0.048 units/ml) enzyme from P. fluorescens MP-13 revealed 100% TMB mortality under in-vitro conditions. The results of this study can be utilized for future crop improvement programs and integrated pest management strategies.
Topics: Animals; Bacterial Proteins; Chitin; Chitinases; Heteroptera; Insecticides; Pest Control, Biological; Pseudomonas fluorescens; RNA, Ribosomal, 16S
PubMed: 28680004
DOI: 10.2323/jgam.2016.11.001 -
Molecules (Basel, Switzerland) Nov 2019The arylacetonitrilase from the bacterium EBC191 has been intensively studied as a model to understand the molecular basis for the substrate-, reaction-, and... (Comparative Study)
Comparative Study Review
The arylacetonitrilase from the bacterium EBC191 has been intensively studied as a model to understand the molecular basis for the substrate-, reaction-, and enantioselectivity of nitrilases. The nitrilase converts various aromatic and aliphatic nitriles to the corresponding acids and varying amounts of the corresponding amides. The enzyme has been analysed by site-specific mutagenesis and more than 50 different variants have been generated and analysed for the conversion of (,)-mandelonitrile and (,)-2-phenylpropionitrile. These comparative analyses demonstrated that single point mutations are sufficient to generate enzyme variants which hydrolyse (,)-mandelonitrile to ()-mandelic acid with an enantiomeric excess (ee) of 91% or to ()-mandelic acid with an ee-value of 47%. The conversion of (,)-2-phenylpropionitrile by different nitrilase variants resulted in the formation of either ()- or ()-2-phenylpropionic acid with ee-values up to about 80%. Furthermore, the amounts of amides that are produced from (,)-mandelonitrile and (,)-2-phenylpropionitrile could be changed by single point mutations between 2%-94% and <0.2%-73%, respectively. The present study attempted to collect and compare the results obtained during our previous work, and to obtain additional general information about the relationship of the amide forming capacity of nitrilases and the enantiomeric composition of the products.
Topics: Acetonitriles; Aminohydrolases; Mutation; Pseudomonas fluorescens; Substrate Specificity
PubMed: 31766372
DOI: 10.3390/molecules24234232 -
Molecules (Basel, Switzerland) Sep 20193-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The...
3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive ACCC 03870 and Gram-negative ATCC 13525 were studied. Scanning electron microscopy (SEM) examination and leakage of alkaline phosphatase (AKP) verified that 3-carene caused more obvious damage to the morphology and wall structure of than . The release of potassium ions and proteins, the reduction in membrane potential (MP), and fluorescein diacetate (FDA) staining further confirmed that the loss of the barrier function of the cell membrane and the leakage of cytoplasmic contents were due to the 3-carene treatment. Furthermore, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATP content indicated that 3-carene could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the results from the fluorescence analysis revealed that 3-carene could probably bind to bacterial DNA and affect the conformation and structure of genomic DNA. These results revealed that 3-carene had strong antibacterial activity against and via membrane damage, bacterial metabolic perturbations, and genomic DNA structure disruption, interfering in cellular functions and even causing cell death.
Topics: Anti-Bacterial Agents; Bicyclic Monoterpenes; Brochothrix; Cell Wall; DNA, Bacterial; Food Microbiology; Membrane Potentials; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Pseudomonas fluorescens
PubMed: 31489899
DOI: 10.3390/molecules24183246 -
FEMS Microbiology Letters Jul 2017Combined experimental evolutionary and molecular biology approaches have been used to investigate the adaptive radiation of Pseudomonas fluorescens SBW25 in static... (Review)
Review
Adaptive radiation of Pseudomonas fluorescens SBW25 in experimental microcosms provides an understanding of the evolutionary ecology and molecular biology of A-L interface biofilm formation.
Combined experimental evolutionary and molecular biology approaches have been used to investigate the adaptive radiation of Pseudomonas fluorescens SBW25 in static microcosms leading to the colonisation of the air-liquid interface by biofilm-forming mutants such as the Wrinkly Spreader (WS). In these microcosms, the ecosystem engineering of the early wild-type colonists establishes the niche space for subsequent WS evolution and colonisation. Random WS mutations occurring in the developing population that deregulate diguanylate cyclases and c-di-GMP homeostasis result in cellulose-based biofilms at the air-liquid interface. These structures allow Wrinkly Spreaders to intercept O2 diffusing into the liquid column and limit the growth of competitors lower down. As the biofilm matures, competition increasingly occurs between WS lineages, and niche divergence within the biofilm may support further diversification before system failure when the structure finally sinks. A combination of pleiotropic and epistasis effects, as well as secondary mutations, may explain variations in WS phenotype and fitness. Understanding how mutations subvert regulatory networks to express intrinsic genome potential and key innovations providing a selective advantage in novel environments is key to understanding the versatility of bacteria, and how selection and ecological opportunity can rapidly lead to substantive changes in phenotype and in community structure and function.
Topics: Adaptation, Physiological; Biofilms; Biological Evolution; Ecology; Ecosystem; Environment; Evolution, Molecular; Genotype; Mutation; Phenotype; Pseudomonas fluorescens; Radiation
PubMed: 28535292
DOI: 10.1093/femsle/fnx109