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Environmental Microbiology Dec 2022Biofilms are essential for plant-associated bacteria to colonize their host. In this work, we analysed the interaction of Azospirillum baldaniorum Sp245 and Pseudomonas...
Biofilms are essential for plant-associated bacteria to colonize their host. In this work, we analysed the interaction of Azospirillum baldaniorum Sp245 and Pseudomonas fluorescens A506 in mixed macrocolony biofilms. We identified certain culture conditions where A. baldaniorum Sp245 exploits P. fluorescens A506 to boost its growth. Azospirillum growth increased proportionally to the initial number of pseudomonads building the biofilm, which in turn were negatively affected in their growth. Physical contact with P. fluorescens A506 was essential for A. baldaniorum Sp245 growth increase. Biofilm ultrastructure analysis revealed that Pseudomonas produces a thick structure that hosts Azospirillum cells in its interior. Additional experimentation demonstrated that Azospirillum growth boost is compromised when interacting with biofilm-deficient Pseudomonas mutants, and that a low oxygen concentration strongly induce A. baldaniorum Sp245 growth, overriding Pseudomonas stimulation. In this line, we used a microaerophilia reporter strain of A. baldaniorum Sp245 to confirm that dual-species macrocolonies contain a higher number of cells under microaerophilic conditions. Taking all the results into consideration, we propose that A. baldaniorum Sp245 can benefit from P. fluorescens A506 partnership in mixed biofilms by taking advantage of the low oxygen concentration and scaffold made up of Pseudomonas-derived matrix, to expand its growth.
Topics: Pseudomonas fluorescens; Azospirillum brasilense; Biofilms; Pseudomonas; Oxygen
PubMed: 36063363
DOI: 10.1111/1462-2920.16195 -
International Journal of Systematic and... Sep 2020A Gram-stain-negative aerobic bacterium, strain 11K1, was isolated from a rhizosphere soil of broad bean collected from Qujing, Yunnan, PR China and characterized by...
A Gram-stain-negative aerobic bacterium, strain 11K1, was isolated from a rhizosphere soil of broad bean collected from Qujing, Yunnan, PR China and characterized by using polyphasic taxonomy. The bacterial cells of strain 11K1 were rod-shaped, motile by two polar flagella and positive for oxidase and catalase. Results of phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain had the highest similarities to DSM 13194 (99.52 %), CFBP 5737 (99.45 %), subsp. s NBRC 3904 (99.31 %), DSM 13647 (99.25 %) and JCM11938 (99.24 %). Multilocus sequence analysis using the 16S rRNA, , and gene sequences demonstrated that strain 11K1 was a member of the subgroup within the lineage, but was distant from all closely related species. The average nucleotide identity and DNA-DNA hybridization values were lower than recommended thresholds of 95 and 70 %, respectively, for species delineation. The major isoprenoid quinone of strain 11K1 was ubiquinone (Q-9) and the major cellular fatty acids were C, summed feature 3 (C ω7/C ω6), summed feature 8 (C ω7/C ω6) and C cyclo. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, aminophospholipid and two unidentified lipids. Based on the results of phenotypic characterization, phylogenetic analysis and genome comparison, strain 11K1 represents a novel species of the genus , for which the name sp. nov. is proposed. The type strain is 11K1 (=GDMCC 1.1743=KACC 21650).
Topics: Bacterial Typing Techniques; Base Composition; China; DNA, Bacterial; Fatty Acids; Genes, Bacterial; Nucleic Acid Hybridization; Phospholipids; Phylogeny; Pseudomonas; RNA, Ribosomal, 16S; Rhizosphere; Soil Microbiology; Ubiquinone; Vicia faba
PubMed: 32776868
DOI: 10.1099/ijsem.0.004373 -
International Journal of Systematic and... Nov 2019An aerobic, Gram-stain-negative, rod-shaped bacterium, designated DMKU BBB3-04, was isolated from bark of mango tree . Colonies were circular, convex with entire margins...
An aerobic, Gram-stain-negative, rod-shaped bacterium, designated DMKU BBB3-04, was isolated from bark of mango tree . Colonies were circular, convex with entire margins when grown on nutrient agar medium for 2 days. The bacterium was motile by means of lophotrichous flagella and produced black-brown pigment. The strain grew at 12-40 °C (optimum, 28-30 °C) and at pH 6.0-8.0 (pH 6.5). Growth was observed in the presence of up to 5 % (w/v) NaCl. Strain DMKU BBB3-04 showed the highest 16S rRNA gene sequence similarity to KF707 (97.1 %), NBRC 103045 (97.0 %), MA-69 (96.9 %) and 6H33b (96.8 %), suggesting that strain DMKU BBB3-04 should be classified within the genus . Analysis of strain DMKU BBB3-04 was also performed using three housekeeping genes (, and ) and further confirmed the phylogenetic assignment of the strain. The major fatty acids found in strain DMKU BBB3-04 were summed feature 8 (C ω7/C ω6), C and summed feature 3 (C ω7/C ω6) (35, 22 and 19 %, respectively). The major polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinone was Q-9. The DNA G+C content of the strain DMKU BBB3-04 was 67.6 mol%. On the basis of phenotypic characteristics, chemotaxonomic data and phylogenetic analysis, strain DMKU BBB3-04 is considered to represent a novel species in the genus . We propose the name sp. nov. for this novel species. The type strain of the novel species is DMKU BBB3-04 (=TBRC 7080=JCM 32061).
Topics: Bacterial Typing Techniques; Base Composition; DNA, Bacterial; Fatty Acids; Genes, Bacterial; Mangifera; Nucleic Acid Hybridization; Phospholipids; Phylogeny; Plant Bark; Pseudomonas; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Thailand; Ubiquinone
PubMed: 31429815
DOI: 10.1099/ijsem.0.003657 -
Microbiology Spectrum Feb 2023Flagellins are the main constituents of the flagellar filaments that provide bacterial motility, chemotactic ability, and host immune elicitation ability. Although the...
Flagellins are the main constituents of the flagellar filaments that provide bacterial motility, chemotactic ability, and host immune elicitation ability. Although the functions of flagellins have been extensively studied in bacteria with a single flagellin-encoding gene, the function of multiple flagellin-encoding genes in a single bacterial species is largely unknown. Here, the model plant-growth-promoting bacterium Pseudomonas kilonensis F113 was used to decipher the divergent functions of duplicated flagellins. We demonstrate that the two flagellins (FliC-1 and FliC-2) in 12 Pseudomonas strains, including F113, are evolutionarily distinct. Only the gene but not the gene in strain F113 is responsible for flagellar biogenesis, motility, and plant immune elicitation. The transcriptional expression of was significantly lower than that of in medium and , most likely due to variations in promoter activity. prediction revealed that all genes in the 12 Pseudomonas strains have a poorly conserved promoter motif. Compared to the Flg22-2 epitope (relative to FliC-2), Flg22-1 (relative to FliC-1) induced stronger FLAGELLIN SENSING 2 (FLS2)-mediated microbe-associated molecular pattern-triggered immunity and significantly inhibited plant root growth. A change in the 19th amino acid in Flg22-2 reduced its binding affinity to the FLS2/brassinosteroid insensitive 1-associated kinase 1 complex. Also, Flg22-2 epitopes in the other 11 Pseudomonas strains were presumed to have low binding affinity due to the same change in the 19th amino acid. These findings suggest that Pseudomonas has evolved duplicate flagellins, with only FliC-1 contributing to motility and plant immune elicitation. Flagellins have emerged as important microbial patterns. This work focuses on flagellin duplication in some plant-associated Pseudomonas. Our findings on the divergence of duplicated flagellins provide a conceptual framework for better understanding the functional determinant flagellin and its peptide in multiple-flagellin plant-growth-promoting rhizobacteria.
Topics: Flagellin; Pseudomonas; Plant Immunity
PubMed: 36629446
DOI: 10.1128/spectrum.03621-22 -
Journal of the Royal Society, Interface Mar 2023Quorum sensing is a widespread process in bacteria that controls collective behaviours in response to cell density. Populations of cells coordinate gene expression...
Quorum sensing is a widespread process in bacteria that controls collective behaviours in response to cell density. Populations of cells coordinate gene expression through the perception of self-produced chemical signals. Although this process is well-characterized genetically and biochemically, quantitative information about network properties, including induction dynamics and steady-state behaviour, is scarce. Here we integrate experiments with mathematical modelling to quantitatively analyse the LasI/LasR quorum sensing pathway in the opportunistic pathogen . We determine key kinetic parameters of the pathway and, using the parametrized model, show that quorum sensing behaves as a bistable hysteretic switch, with stable on and off states. We investigate the significance of feedback architecture and find that positive feedback on signal production is critical for induction dynamics and bistability, whereas positive feedback on receptor expression and negative feedback on signal production play a minor role. Taken together, our data-based modelling approach reveals fundamental and emergent properties of a bacterial quorum sensing circuit, and provides evidence that native quorum sensing can indeed function as the gene expression switch it is commonly perceived to be.
Topics: Pseudomonas; Pseudomonas aeruginosa; Quorum Sensing; Bacterial Proteins; Gene Expression; Gene Expression Regulation, Bacterial
PubMed: 36919437
DOI: 10.1098/rsif.2022.0825 -
Environmental Microbiology Reports Jun 2022Assistive eco-physiological traits are necessary for microbes to adapt and colonize at polluted niches, enabling efficient clean-up. To demarcate species distinctiveness...
Assistive eco-physiological traits are necessary for microbes to adapt and colonize at polluted niches, enabling efficient clean-up. To demarcate species distinctiveness and eco-physiological traits of aromatic compounds metabolizing Pseudomonas sp. CSV86 (earlier identified as Pseudomonas putida), an Indian isolate from a petrol station soil, comparative genome mining, taxono-genomic, and physiological analyses were performed. A 6.79 Mbp genome (62.72 G + C mol%) of CSV86 encodes 6798 CDS and 238 unique genes. Naphthalene metabolism and Co-Zn-Cd resistance gene clusters were part of distinct genomic islands. Abundance of transporters (aromatics, organic acids, amino acids, and metals) and mobile elements (integrases, transposases, conjugative proteins) differentiated CSV86 from its closest relatives. Enhanced siderophore production for Fe-uptake during aromatic metabolism, indole acetic acid production, and fusaric acid resistance wasvalidated by genomic attributes. Full-length 16S-rRNA phylogeny revealed Pseudomonas japonica WL as a closest relative of CSV86 . However, lower genomic indices (<97% gyrB-rpoB-rpoD homology, <90% ANI, <50% DNA-DNA relatedness) and taxonomic differences (assimilation of organic acids, amino acids, fatty acids composition) substantially differentiated CSV86 from its closest relatives, indicating it to be a novel species as Pseudomonas bharatica. Preferential metabolism of aromatics with advantageous eco-physiological traits renders CSV86 an ideal candidate for bioremediation and host for metabolic engineering.
Topics: Amino Acids; Bacterial Typing Techniques; DNA, Bacterial; Fatty Acids; Genes, Bacterial; Genomics; Phylogeny; Pseudomonas; Pseudomonas putida; RNA, Ribosomal, 16S; Sequence Analysis, DNA
PubMed: 35388632
DOI: 10.1111/1758-2229.13066 -
PLoS Genetics Jun 2024Bacteria use diverse strategies and molecular machinery to maintain copper homeostasis and to cope with its toxic effects. Some genetic elements providing copper...
Bacteria use diverse strategies and molecular machinery to maintain copper homeostasis and to cope with its toxic effects. Some genetic elements providing copper resistance are acquired by horizontal gene transfer; however, little is known about how they are controlled and integrated into the central regulatory network. Here, we studied two copper-responsive systems in a clinical isolate of Pseudomonas paraeruginosa and deciphered the regulatory and cross-regulation mechanisms. To do so, we combined mutagenesis, transcriptional fusion analyses and copper sensitivity phenotypes. Our results showed that the accessory CusRS two-component system (TCS) responds to copper and activates both its own expression and that of the adjacent nine-gene operon (the pcoA2 operon) to provide resistance to elevated levels of extracellular copper. The same locus was also found to be regulated by two core-genome-encoded TCSs-the copper-responsive CopRS and the zinc-responsive CzcRS. Although the target palindromic sequence-ATTCATnnATGTAAT-is the same for the three response regulators, transcriptional outcomes differ. Thus, depending on the operon/regulator pair, binding can result in different activation levels (from none to high), with the systems demonstrating considerable plasticity. Unexpectedly, although the classical CusRS and the noncanonical CopRS TCSs rely on distinct signaling mechanisms (kinase-based vs. phosphatase-based), we discovered cross-talk in the absence of the cognate sensory kinases. This cross-talk occurred between the proteins of these two otherwise independent systems. The cusRS-pcoA2 locus is part of an Integrative and Conjugative Element and was found in other Pseudomonas strains where its expression could provide copper resistance under appropriate conditions. The results presented here illustrate how acquired genetic elements can become part of endogenous regulatory networks, providing a physiological advantage. They also highlight the potential for broader effects of accessory regulatory proteins through interference with core regulatory proteins.
Topics: Copper; Pseudomonas; Gene Expression Regulation, Bacterial; Operon; Bacterial Proteins; Drug Resistance, Bacterial; Signal Transduction
PubMed: 38861577
DOI: 10.1371/journal.pgen.1011325 -
Journal of the Science of Food and... Aug 2019Pseudomonas are part of the indigenous microbiota of different foods, where they gradually cause spoilage. In fish meat, Pseudomonas fragi and Pseudomonas psychrophila...
BACKGROUND
Pseudomonas are part of the indigenous microbiota of different foods, where they gradually cause spoilage. In fish meat, Pseudomonas fragi and Pseudomonas psychrophila have been identified as important spoilers. The initial aim of this study was to investigate the physiological characteristics, adhesion, and biofilm of P. fragi and P. psychrophila under temperatures related to the fish-processing industry. The further aim was to define the problem of increased growth of pathogenic bacteria in the presence of spoilage bacteria in vitro and in fish meat.
RESULTS
Temperature dependence on physiological characteristics, adhesion, and biofilm was observed. Hydrophobicity and autoaggregation were most prominent at 15 °C, and at this temperature floating biofilm was also formed. The adhesion of these Pseudomonas was up to 2 log CFU cm more pronounced on stainless steel than polystyrene, with up to five times greater biofilm biomass production at 5 °C on polystyrene. This paralleled at least a 0.5 log CFU g increase in the pathogenic bacterium Escherichia coli in fish meat.
CONCLUSION
Pseudomonas fragi and P. psychrophila adhesion and biofilm depend on the temperature, and are stimulated by temperatures that can occur during the processing and storage of fish meat. Strong Pseudomonas biofilm formation under refrigeration conditions is protective for E. coli, potentially by providing more favorable conditions by ensuring a higher concentration of nutrients. Interactions between spoilage Pseudomonas and pathogenic bacteria can occur through different mechanisms, and an understanding of these is of particular importance to ensure the overall quality and safety of fish meat and other proteinaceous foods. © 2019 Society of Chemical Industry.
Topics: Animals; Biofilms; Colony Count, Microbial; Escherichia coli; Fishes; Food Handling; Food Microbiology; Pseudomonas; Seafood; Temperature
PubMed: 30895626
DOI: 10.1002/jsfa.9703 -
Infection, Genetics and Evolution :... Sep 2023Plant pathogenic Pseudomonas species use multiple classes of toxins and virulence factors during host infection. The genes encoding these pathogenicity factors are often...
Plant pathogenic Pseudomonas species use multiple classes of toxins and virulence factors during host infection. The genes encoding these pathogenicity factors are often located on plasmids and other mobile genetic elements, suggesting that they are acquired through horizontal gene transfer to confer an evolutionary advantage for successful adaptation to host infection. However, the genetic rearrangements that have led to mobilization of the pathogenicity genes are not fully understood. In this study, we have sequenced and analyzed the complete genome sequences of four Pseudomonas amygdali pv. aesculi (Pae), which infect European horse chestnut trees (Aesculus hippocastanum) and belong to phylogroup 3 of the P. syringae species complex. The four investigated genomes contain six groups of plasmids that all encode pathogenicity factors. Effector genes were found to be mostly associated with insertion sequence elements, suggesting that virulence genes are generally mobilized and potentially undergo horizontal gene transfer after transfer to a conjugative plasmid. We show that the biosynthetic gene cluster encoding the phytotoxin coronatine was recently transferred from a chromosomal location to a mobilizable plasmid that subsequently formed a co-integrate with a conjugative plasmid.
Topics: Pseudomonas; Plasmids; Virulence Factors
PubMed: 37541538
DOI: 10.1016/j.meegid.2023.105486 -
Applied and Environmental Microbiology Jan 2021Fluorescent spp. producing the antibiotic 2,4-diacetylphloroglucinol (DAPG) are ecologically important in the rhizosphere, as they can control phytopathogens and...
Fluorescent spp. producing the antibiotic 2,4-diacetylphloroglucinol (DAPG) are ecologically important in the rhizosphere, as they can control phytopathogens and contribute to disease suppression. DAPG can also trigger a systemic resistance response in plants and stimulate root exudation and branching as well as induce plant-beneficial activities in other rhizobacteria. While studies of DAPG-producing have predominantly focused on rhizosphere niches, the ecological role of DAPG as well as the distribution and dynamics of DAPG-producing bacteria remains less well understood for other environments, such as bulk soil and grassland, where the level of DAPG producers are predicted to be low. In this study, we constructed a whole-cell biosensor for detection of DAPG and DAPG-producing bacteria from environmental samples. The constructed biosensor contains a response module and either or genes as output modules assembled on a pSEVA plasmid backbone for easy transfer to different host species and to enable easy future genetic modifications. We show that the sensor is highly specific toward DAPG, with a sensitivity in the low nanomolar range (>20 nM). This sensitivity is comparable to the DAPG levels identified in rhizosphere samples by chemical analysis. The biosensor enables guided isolation of DAPG-producing Using the biosensor, we probed the same grassland soil sampling site to isolate genetically related DAPG-producing strains over a period of 12 months. Next, we used the biosensor to determine the frequency of DAPG-producing pseudomonads within three different grassland soil sites and showed that DAPG producers can constitute part of the population in the range of 0.35 to 17% at these sites. Finally, we showed that the biosensor enables detection of DAPG produced by non- species. Our study shows that a whole-cell biosensor for DAPG detection can facilitate isolation of bacteria that produce this important secondary metabolite and provide insight into the population dynamics of DAPG producers in natural grassland soil. The interest in bacterial biocontrol agents as biosustainable alternatives to pesticides to increase crop yields has grown. To date, we have a broad knowledge of antimicrobial compounds, such as DAPG, produced by bacteria growing in the rhizosphere surrounding plant roots. However, compared to the rhizosphere niches, the ecological role of DAPG as well as the distribution and dynamics of DAPG-producing bacteria remains less well understood for other environments, such as bulk and grassland soil. Currently, we are restricted to chemical methods with detection limits and time-consuming PCR-based and probe hybridization approaches to detect DAPG and its respective producer. In this study, we developed a whole-cell biosensor, which can circumvent the labor-intensive screening process as well as increase the sensitivity at which DAPG can be detected. This enables quantification of relative amounts of DAPG producers, which, in turn, increases our understanding of the dynamics and ecology of these producers in natural soil environments.
Topics: Biosensing Techniques; Grassland; Pest Control, Biological; Phloroglucinol; Pseudomonas; Soil; Soil Microbiology
PubMed: 33218996
DOI: 10.1128/AEM.01400-20