scholarly journals Rhizosphere Selection of Highly Motile Phenotypic Variants of Pseudomonas fluorescens with Enhanced Competitive Colonization Ability

2006 ◽  
Vol 72 (5) ◽  
pp. 3429-3434 ◽  
Author(s):  
Francisco Mart�nez-Granero ◽  
Rafael Rivilla ◽  
Marta Mart�n
Keyword(s):  
Pseudomonas Fluorescens ◽  
Type Strain ◽  
Wild Type Strain ◽  
Root Tip ◽  
Wild Type ◽  
Swimming Motility ◽  
Rhizosphere Colonization ◽  
Prolonged Cultivation ◽  
Genes Encoding ◽  
Different Populations

ABSTRACT Phenotypic variants of Pseudomonas fluorescens F113 showing a translucent and diffuse colony morphology show enhanced colonization of the alfalfa rhizosphere. We have previously shown that in the biocontrol agent P. fluorescens F113, phenotypic variation is mediated by the activity of two site-specific recombinases, Sss and XerD. By overexpressing the genes encoding either of the recombinases, we have now generated a large number of variants (mutants) after selection either by prolonged laboratory cultivation or by rhizosphere passage. All the isolated variants were more motile than the wild-type strain and appear to contain mutations in the gacA and/or gacS gene. By disrupting these genes and complementation analysis, we have observed that the Gac system regulates swimming motility by a repression pathway. Variants isolated after selection by prolonged cultivation formed a single population with a swimming motility that was equal to the motility of gac mutants, being 150% more motile than the wild type. The motility phenotype of these variants was complemented by the cloned gac genes. Variants isolated after rhizosphere selection belonged to two different populations: one identical to the population isolated after prolonged cultivation and the other comprising variants that besides a gac mutation harbored additional mutations conferring higher motility. Our results show that gac mutations are selected both in the stationary phase and during rhizosphere colonization. The enhanced motility phenotype is in turn selected during rhizosphere colonization. Several of these highly motile variants were more competitive than the wild-type strain, displacing it from the root tip within 2 weeks.

scholarly journals Involvement of RpoN in Regulating Motility, Biofilm, Resistance, and Spoilage Potential of Pseudomonas fluorescens

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiaoxiang Liu ◽  
Yifan Ye ◽  
Yin Zhu ◽  
Lifang Wang ◽  
Leyang Yuan ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory Function ◽  
Rna Seq ◽  
Wild Type ◽  
Swimming Motility ◽  
Cellular Processes ◽  
Food Quality And Safety

Pseudomonas fluorescens is a typical spoiler of proteinaceous foods, and it is characterized by high spoilage activity. The sigma factor RpoN is a well-known regulator controlling nitrogen assimilation and virulence in many pathogens. However, its exact role in regulating the spoilage caused by P. fluorescens is unknown. Here, an in-frame deletion mutation of rpoN was constructed to investigate its global regulatory function through phenotypic and RNA-seq analysis. The results of phenotypic assays showed that the rpoN mutant was deficient in swimming motility, biofilm formation, and resistance to heat and nine antibiotics, while the mutant increased the resistance to H2O2. Moreover, the rpoN mutant markedly reduced extracellular protease and total volatile basic nitrogen (TVB-N) production in sterilized fish juice at 4°C; meanwhile, the juice with the rpoN mutant showed significantly higher sensory scores than that with the wild-type strain. To identify RpoN-controlled genes, RNA-seq-dependent transcriptomics analysis of the wild-type strain and the rpoN mutant was performed. A total of 1224 genes were significantly downregulated, and 474 genes were significantly upregulated by at least two folds at the RNA level in the rpoN mutant compared with the wild-type strain, revealing the involvement of RpoN in several cellular processes, mainly flagellar mobility, adhesion, polysaccharide metabolism, resistance, and amino acid transport and metabolism; this may contribute to the swimming motility, biofilm formation, stress and antibiotic resistance, and spoilage activities of P. fluorescens. Our results provide insights into the regulatory role of RpoN of P. fluorescens in food spoilage, which can be valuable to ensure food quality and safety.

scholarly journals Pseudomonas fluorescens F113 Mutant with Enhanced Competitive Colonization Ability and Improved Biocontrol Activity against Fungal Root Pathogens

2011 ◽  
Vol 77 (15) ◽  
pp. 5412-5419 ◽  
Author(s):  
Emma Barahona ◽  
Ana Navazo ◽  
Francisco Martínez-Granero ◽  
Teresa Zea-Bonilla ◽  
Rosa María Pérez-Jiménez ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Secondary Metabolism ◽  
Type Strain ◽  
Wild Type Strain ◽  
Biocontrol Agents ◽  
Wild Type ◽  
Content Type ◽  
Rhizosphere Colonization ◽  
Biocontrol Activity ◽  
Colonization Ability

ABSTRACTMotility is one of the most important traits for efficient rhizosphere colonization byPseudomonas fluorescensF113rif (F113). In this bacterium, motility is a polygenic trait that is repressed by at least three independent pathways, including the Gac posttranscriptional system, the Wsp chemotaxis-like pathway, and the SadB pathway. Here we show that thekinBgene, which encodes a signal transduction protein that together with AlgB has been implicated in alginate production, participates in swimming motility repression through the Gac pathway, acting downstream of the GacAS two-component system. Gac mutants are impaired in secondary metabolite production and are unsuitable as biocontrol agents. However, thekinBmutant and a triple mutant affected inkinB,sadB, andwspR(KSW) possess a wild-type phenotype for secondary metabolism. The KSW strain is hypermotile and more competitive for rhizosphere colonization than the wild-type strain. We have compared the biocontrol activity of KSW with those of the wild-type strain and a phenotypic variant (F113v35 [V35]) which is hypermotile and hypercompetitive but is affected in secondary metabolism since it harbors agacSmutation. Biocontrol experiments in theFusarium oxysporumf. sp.radicis-lycopersici/Lycopersicum esculentum(tomato) andPhytophthora cactorum/Fragaria vesca(strawberry) pathosystems have shown that the three strains possess biocontrol activity. Biocontrol activity was consistently lower for V35, indicating that the production of secondary metabolites was the most important trait for biocontrol. Strain KSW showed improved biocontrol compared with the wild-type strain, indicating that an increase in competitive colonization ability resulted in improved biocontrol and that the rational design of biocontrol agents by mutation is feasible.

scholarly journals Expression and function of the cdgD gene, encoding a CHASE–PAS-DGC-EAL domain protein, in Azospirillum brasilense

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Francisco Cruz-Pérez ◽  
Roxana Lara-Oueilhe ◽  
Cynthia Marcos-Jiménez ◽  
Ricardo Cuatlayotl-Olarte ◽  
María Luisa Xiqui-Vázquez ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Soil Conditions ◽  
Wild Type ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Genes Encoding ◽  
In The Wild ◽  
Plant Growth Promoting

AbstractThe plant growth-promoting bacterium Azospirillum brasilense contains several genes encoding proteins involved in the biosynthesis and degradation of the second messenger cyclic-di-GMP, which may control key bacterial functions, such as biofilm formation and motility. Here, we analysed the function and expression of the cdgD gene, encoding a multidomain protein that includes GGDEF-EAL domains and CHASE and PAS domains. An insertional cdgD gene mutant was constructed, and analysis of biofilm and extracellular polymeric substance production, as well as the motility phenotype indicated that cdgD encoded a functional diguanylate protein. These results were correlated with a reduced overall cellular concentration of cyclic-di-GMP in the mutant over 48 h compared with that observed in the wild-type strain, which was recovered in the complemented strain. In addition, cdgD gene expression was measured in cells growing under planktonic or biofilm conditions, and differential expression was observed when KNO3 or NH4Cl was added to the minimal medium as a nitrogen source. The transcriptional fusion of the cdgD promoter with the gene encoding the autofluorescent mCherry protein indicated that the cdgD gene was expressed both under abiotic conditions and in association with wheat roots. Reduced colonization of wheat roots was observed for the mutant compared with the wild-type strain grown in the same soil conditions. The Azospirillum-plant association begins with the motility of the bacterium towards the plant rhizosphere followed by the adsorption and adherence of these bacteria to plant roots. Therefore, it is important to study the genes that contribute to this initial interaction of the bacterium with its host plant.

scholarly journals Comparative analysis and mutation effects of fpp2–fpp1 tandem genes encoding proteolytic extracellular enzymes of Flavobacterium psychrophilum

Microbiology ◽  
2011 ◽  
Vol 157 (4) ◽  
pp. 1196-1204 ◽  
Author(s):  
David Pérez-Pascual ◽  
Esther Gómez ◽  
Beatriz Álvarez ◽  
Jessica Méndez ◽  
Pilar Reimundo ◽  
...  
Keyword(s):  
Gene Function ◽  
Type Strain ◽  
Wild Type Strain ◽  
Proteolytic Enzymes ◽  
Function Analysis ◽  
Phenotypic Characterization ◽  
Pcr Analysis ◽  
Wild Type ◽  
Flavobacterium Psychrophilum ◽  
Genes Encoding

Flavobacterium psychrophilum is a very significant fish pathogen that secretes two biochemically characterized extracellular proteolytic enzymes, Fpp1 and Fpp2. The genes encoding these enzymes are organized as an fpp2–fpp1 tandem in the genome of strain F. psychrophilum THC02/90. Analysis of the corresponding encoded proteins showed that they belong to two different protease families. For gene function analysis, new genetic tools were developed in F. psychrophilum by constructing stable isogenic fpp1 and fpp2 mutants via single-crossover homologous recombination. RT-PCR analysis of wild-type and mutant strains suggested that both genes are transcribed as a single mRNA from the promoter located upstream of the fpp2 gene. Phenotypic characterization of the fpp2 mutant showed lack of caseinolytic activity and higher colony spreading compared with the wild-type strain. Both characteristics were recovered in the complemented strain. One objective of this work was to assess the contribution to virulence of these proteolytic enzymes. LD50 experiments using the wild-type strain and mutants showed no significant differences in virulence in a rainbow trout challenge model, suggesting instead a possible nutritional role. The gene disruption procedure developed in this work, together with the knowledge of the complete genome sequence of F. psychrophilum, open new perspectives for the study of gene function in this bacterium.

scholarly journals Effects of Deletion of Genes Encoding Fe-Only Hydrogenase of Desulfovibrio vulgaris Hildenborough on Hydrogen and Lactate Metabolism

2002 ◽  
Vol 184 (3) ◽  
pp. 679-686 ◽  
Author(s):  
Brant K. J. Pohorelic ◽  
Johanna K. Voordouw ◽  
Elisabeth Lojou ◽  
Alain Dolla ◽  
Jens Harder ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Electron Donor ◽  
Type Strain ◽  
Wild Type Strain ◽  
Physiological Role ◽  
Hydrogen Uptake ◽  
Desulfovibrio Vulgaris ◽  
Lactate Metabolism ◽  
Wild Type ◽  
Genes Encoding

ABSTRACT The physiological properties of a hyd mutant of Desulfovibrio vulgaris Hildenborough, lacking periplasmic Fe-only hydrogenase, have been compared with those of the wild-type strain. Fe-only hydrogenase is the main hydrogenase of D. vulgaris Hildenborough, which also has periplasmic NiFe- and NiFeSe-hydrogenases. The hyd mutant grew less well than the wild-type strain in media with sulfate as the electron acceptor and H2 as the sole electron donor, especially at a high sulfate concentration. Although the hyd mutation had little effect on growth with lactate as the electron donor for sulfate reduction when H2 was also present, growth in lactate- and sulfate-containing media lacking H2 was less efficient. The hyd mutant produced, transiently, significant amounts of H2 under these conditions, which were eventually all used for sulfate reduction. The results do not confirm the essential role proposed elsewhere for Fe-only hydrogenase as a hydrogen-producing enzyme in lactate metabolism (W. A. M. van den Berg, W. M. A. M. van Dongen, and C. Veeger, J. Bacteriol. 173:3688–3694, 1991). This role is more likely played by a membrane-bound, cytoplasmic Ech-hydrogenase homolog, which is indicated by the D. vulgaris genome sequence. The physiological role of periplasmic Fe-only hydrogenase is hydrogen uptake, both when hydrogen is and when lactate is the electron donor for sulfate reduction.

scholarly journals Insights into an alternative pathway for glycerol metabolism in a glycerol kinase deficientPseudomonas putidaKT2440

2019 ◽  
Author(s):  
Meg Walsh ◽  
William Casey ◽  
Shane T. Kenny ◽  
Tanja Narancic ◽  
Lars M. Blank ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Alternative Pathway ◽  
Glycerol Kinase ◽  
Glycerol Metabolism ◽  
Wild Type ◽  
Short Chain Length ◽  
Genes Encoding ◽  
In The Wild

AbstractPseudomonas putidaKT2440 is known to metabolise glycerol via glycerol-3-phosphate using glycerol kinase an enzyme previously described as critical for glycerol metabolism (1). However, when glycerol kinase was knocked out inP. putidaKT2440 it retained the ability to use glycerol as the sole carbon source, albeit with a much-extended lag period and 2 fold lower final biomass compared to the wild type strain. A metabolomic study identified glycerate as a major and the most abundant intermediate in glycerol metabolism in this mutated strain with levels 21-fold higher than wild type. Erythrose-4-phosphate was detected in the mutant strain, but not in the wild type strain. Glyceraldehyde and glycraldehyde-3-phosphate were detected at similar levels in the mutant strain and the wild type. Transcriptomic studies identified 191 genes that were more than 2-fold upregulated in the mutant compared to the wild type and 175 that were down regulated. The genes involved in short chain length fatty acid metabolism were highly upregulated in the mutant strain. The genes encoding 3-hydroxybutyrate dehydrogenase were 5.8-fold upregulated and thus the gene was cloned, expressed and purified to reveal it can act on glyceraldehyde but not glycerol as a substrate.

scholarly journals Redox-Dependent Gene Regulation inRhodobacter sphaeroides 2.4.1T: Effects on Dimethyl Sulfoxide Reductase (dor) Gene Expression

1998 ◽  
Vol 180 (21) ◽  
pp. 5612-5618 ◽  
Author(s):  
Nigel J. Mouncey ◽  
Samuel Kaplan
Keyword(s):  
Gene Expression ◽  
Dimethyl Sulfoxide ◽  
Type Strain ◽  
Wild Type Strain ◽  
Strictly Aerobic ◽  
Wild Type ◽  
Dmso Reductase ◽  
Regulatory Cascade ◽  
Expression Of Genes ◽  
Genes Encoding

ABSTRACT The ability of Rhodobacter sphaeroides2.4.1T to respire anaerobically with the alternative electron acceptor dimethyl sulfoxide (DMSO) or trimethylamineN-oxide (TMAO) is manifested by the molybdoenzyme DMSO reductase, which is encoded by genes of the dor locus. Previously, we have demonstrated that dor expression is regulated in response to lowered oxygen tensions and the presence of DMSO or TMAO in the growth medium. Several regulatory proteins have been identified as key players in this regulatory cascade: FnrL, DorS-DorR, and DorX-DorY. To further examine the role of redox potentiation in the regulation of dor expression, we measured DMSO reductase synthesis and β-galactosidase activity fromdor::lacZ fusions in strains containing mutations in the redox-active proteins CcoP and RdxB, which have previously been implicated in the generation of a redox signal affecting photosynthesis gene expression. Unlike the wild-type strain, both mutants were able to synthesize DMSO reductase under strictly aerobic conditions, even in the absence of DMSO. When cells were grown photoheterotrophically, dorC::lacZexpression was stimulated by increasing light intensity in the CcoP mutant, whereas it is normally repressed in the wild-type strain under such conditions. Furthermore, the expression of genes encoding the DorS sensor kinase and DorR response regulator proteins was also affected by the ccoP mutation. By using CcoP-DorR and CcoP-DorY double mutants, it was shown that the DorR protein is strictly required for altered dor expression in CcoP mutants. These results further demonstrate a role for redox-generated responses in the expression of genes encoding DMSO reductase in R. sphaeroides and identify the DorS-DorR proteins as a redox-dependent regulatory system controlling dorexpression.

scholarly journals Nitrite and Nitrous Oxide Reductase Regulation by Nitrogen Oxides in Rhodobacter sphaeroides f. sp.denitrificans IL106

1999 ◽  
Vol 181 (19) ◽  
pp. 6028-6032 ◽  
Author(s):  
Monique Sabaty ◽  
Carole Schwintner ◽  
Sandrine Cahors ◽  
Pierre Richaud ◽  
Andre Verméglio
Keyword(s):  
Nitrous Oxide ◽  
Nitrate Reductase ◽  
Rhodobacter Sphaeroides ◽  
Type Strain ◽  
Biochemical Analysis ◽  
Wild Type Strain ◽  
Nitrous Oxide Reductase ◽  
Wild Type ◽  
Genes Encoding ◽  
Membrane Bound

ABSTRACT We have cloned the nap locus encoding the periplasmic nitrate reductase in Rhodobacter sphaeroides f. sp.denitrificans IL106. A mutant with this enzyme deleted is unable to grow under denitrifying conditions. Biochemical analysis of this mutant shows that in contrast to the wild-type strain, the level of synthesis of the nitrite and N2O reductases is not increased by the addition of nitrate. Growth under denitrifying conditions and induction of N oxide reductase synthesis are both restored by the presence of a plasmid containing the genes encoding the nitrate reductase. This demonstrates that R. sphaeroides f. sp. denitrificans IL106 does not possess an efficient membrane-bound nitrate reductase and that nitrate is not the direct inducer for the nitrite and N2O reductases in this species. In contrast, we show that nitrite induces the synthesis of the nitrate reductase.

scholarly journals Nine Mutants of Chlorobium tepidum Each Unable To Synthesize a Different Chlorosome Protein Still Assemble Functional Chlorosomes

2004 ◽  
Vol 186 (3) ◽  
pp. 646-653 ◽  
Author(s):  
Niels-Ulrik Frigaard ◽  
Hui Li ◽  
Kirstin J. Milks ◽  
Donald A. Bryant
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Protein Composition ◽  
Chlorobium Tepidum ◽  
Protein Species ◽  
Wild Type ◽  
Absorbance Maximum ◽  
Genes Encoding ◽  
Green Sulfur ◽  
Photosynthetic Antenna

ABSTRACT Chlorosomes of the green sulfur bacterium Chlorobium tepidum comprise mostly bacteriochlorophyll c (BChl c), small amounts of BChl a, carotenoids, and quinones surrounded by a lipid-protein envelope. These structures contain 10 different protein species (CsmA, CsmB, CsmC, CsmD, CsmE, CsmF, CsmH, CsmI, CsmJ, and CsmX) but contain relatively little total protein compared to other photosynthetic antenna complexes. Except for CsmA, which has been suggested to bind BChl a, the functions of the chlorosome proteins are not known. Nine mutants in which a single csm gene was inactivated were created; these mutants included genes encoding all chlorosome proteins except CsmA. All mutants had BChl c contents similar to that of the wild-type strain and had growth rates indistinguishable from or within ∼90% (CsmC− and CsmJ−) of those of the wild-type strain. Chlorosomes isolated from the mutants lacked only the protein whose gene had been inactivated and were generally similar to those from the wild-type strain with respect to size, shape, and BChl c, BChl a, and carotenoid contents. However, chlorosomes from the csmC mutant were about 25% shorter than those from the wild-type strain, and the BChl c absorbance maximum was blue-shifted about 8 nm, indicating that the structure of the BChl c aggregates in these chlorosomes is altered. The results of the present study establish that, except with CsmA, when the known chlorosome proteins are eliminated individually, none of them are essential for the biogenesis, light harvesting, or structural organization of BChl c and BChl a within the chlorosome. These results demonstrate that chlorosomes are remarkably robust structures that can tolerate considerable changes in protein composition.

scholarly journals The adnA Transcriptional Factor Affects Persistence and Spread of Pseudomonas fluorescens under Natural Field Conditions

2001 ◽  
Vol 67 (2) ◽  
pp. 852-857 ◽  
Author(s):  
Bonnie Marshall ◽  
Eduardo A. Robleto ◽  
Richard Wetzler ◽  
Peter Kulle ◽  
Paul Casaz ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Type Strain ◽  
Wild Type Strain ◽  
Transcriptional Factor ◽  
Field Conditions ◽  
Insertion Mutant ◽  
Wild Type ◽  
Natural Field ◽  
Fitness Advantage ◽  
Inoculation Site

ABSTRACT A soil plot was inoculated with a mixture of Pseudomonas fluorescens Pf0-2, the wild type, and Pf0-5a, a Tn5insertion mutant in adnA, at 7.84 log CFU/g of soil. Over a period of 231 days, culturable populations of both strains were measured at selected times below and away from the point of inoculation. Pf0-5a did not spread as fast and attained significantly lower populations than Pf0-2. At sample depths below the inoculation site, the adnA mutant showed a significant decrease in CFU/g of soil as compared to Pf0-2. Pf0-2 was first detected at the 1.5-cm annular site at 3 days after inoculation, whereas Pf0-5a required 7 days to travel the same distance. At this distance, the wild-type strain could be detected at a 21.5- to 25-cm depth, whereas Pf0-5a could be detected only as deep as 15.5 to 18 cm. At 4.5 cm from the site of inoculation and in soil fractions corresponding to 13 to 18 cm, Pf0-2 was the only strain detected. These results suggest that the transcription factor AdnA provides a fitness advantage in P. fluorescens, allowing it to spread and survive in soil under field conditions.

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