A Two-Component System Plays an Important Role in the Root-Colonizing Ability of <i>Pseudomonas fluorescens</i> Strain WCS365

Dekkers, Linda C.; Bloemendaal, C.-J. P.; Weger, Letty A. de; Wijffelman, C. A.; Spaink, H. P.; Lugtenberg, Ben

doi:10.1094/mpmi.1998.11.1.45

Cited by 106 publications

(117 citation statements)

References 58 publications

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“…In line with this, it was shown that transposition of the catabolic transposon Tn4652 in nutrient-starved Pseudomonas putida (104) is triggered by environmental cues through a two-component system, ColR-ColS. This signal relay system was previously identified as an important root colonization factor in Pseudomonas fluorescens (49).…”

Section: Genes Involved In Transposition Andmentioning

confidence: 77%

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

Rediers

Rainey

Vanderleyden

et al. 2005

Microbiol Mol Biol Rev

140

120

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A major challenge for microbiologists is to elucidate the strategies deployed by microorganisms to adapt to and thrive in highly complex and dynamic environments. In vitro studies, including those monitoring genomewide changes, have proven their value, but they can, at best, mimic only a subset of the ensemble of abiotic and biotic stimuli that microorganisms experience in their natural habitats. The widely used gene-to-phenotype approach involves the identification of altered niche-related phenotypes on the basis of gene inactivation. However, many traits contributing to ecological performance that, upon inactivation, result in only subtle or difficult to score phenotypic changes are likely to be overlooked by this otherwise powerful approach. Based on the premise that many, if not most, of the corresponding genes will be induced or upregulated in the environment under study, ecologically significant genes can alternatively be traced using the promoter trap techniques differential fluorescence induction and in vivo expression technology (IVET). The potential and limitations are discussed for the different IVET selection strategies and system-specific variants thereof. Based on a compendium of genes that have emerged from these promoter-trapping studies, several functional groups have been distinguished, and their physiological relevance is illustrated with follow-up studies of selected genes. In addition to confirming results from largely complementary approaches such as signature-tagged mutagenesis, some unexpected parallels as well as distinguishing features of microbial phenotypic acclimation in diverse environmental niches have surfaced. On the other hand, by the identification of a large proportion of genes with unknown function, these promoter-trapping studies underscore how little we know about the secret lives of bacteria and other microorganisms

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Section: Genes Involved In Transposition Andmentioning

confidence: 77%

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

Rediers

Rainey

Vanderleyden

et al. 2005

Microbiol Mol Biol Rev

140

120

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“…Motility was tested as described by Dekkers et al (5). Briefly, KB was diluted 20-fold, semisolidified with 0.3% agar (Select agar), and poured into petri dishes.…”

Section: Methodsmentioning

confidence: 99%

Generation of Enhanced Competitive Root-Tip-Colonizing Pseudomonas Bacteria through Accelerated Evolution

et al. 2004

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A recently published procedure to enrich for efficient competitive root tip colonizers (I. Kuiper, G. V. Bloemberg, and B. J. J. Lugtenberg, Mol. Plant-Microbe Interact. 14:1197-1205) after bacterization of seeds was applied to isolate efficient competitive root tip colonizers for both the dicotyledenous plant tomato and the monocotyledenous plant grass from a random Tn5luxAB mutant bank of the good root colonizer Pseudomonas fluorescens WCS365. Unexpectedly, the best-colonizing mutant, strain PCL1286, showed a strongly enhanced competitive root-tip-colonizing phenotype. Sequence analyses of the Tn5luxAB flanking regions showed that the transposon had inserted in a mutY homolog. This gene is involved in the repair of A ⅐ G mismatches caused by spontaneous oxidation of guanine. We hypothesized that, since the mutant is defective in repairing its mismatches, its cells harbor an increased number of mutations and therefore can adapt faster to the environment of the root system. To test this hypothesis, we constructed another mutY mutant and analyzed its competitive root tip colonization behavior prior to and after enrichment. As a control, a nonmutated wild type was subjected to the enrichment procedure. The results of these analyses showed (i) that the enrichment procedure did not alter the colonization ability of the wild type, (ii) that the new mutY mutant was strongly impaired in its colonization ability, but (iii) that after three enrichment cycles it colonized significantly better than its wild type. Therefore it is concluded that both the mutY mutation and the selection procedure are required to obtain an enhanced root-tip-colonizing mutant.Competitive root tip colonization by Pseudomonas strains can play an important role in the efficient control of soilborne crop diseases caused by fungi (17,30,36,40). Inadequate colonization is often the limiting factor in biocontrol (3,30,39). Pseudomonas fluorescens WCS365 is an excellent colonizer of various plant root systems. To study competitive root tip colonization, we decided to characterize colonization traits and genes. The results of multiple studies have recently been reviewed by Lugtenberg et al. (18). Among the colonization mutants a mutant was found which is impaired in competitive root tip colonization and mutated in a gene with homology to the sss gene from Pseudomonas aeruginosa (7). This gene encodes a protein belonging to the integrase family of sitespecific recombinases involved in DNA rearrangements. The role of the sss homologue in colonization is proposed to be through genetic rearrangements causing different phenotypes. This colonization mutant is assumed to be locked in a phase that is not suitable for competitive colonization in the rhizosphere. Introduction of the sss gene into the poor colonizer P. fluorescens WCS307 and into the good colonizer P. fluorescens F113 improved competitive root-tip-colonizing abilities of these strains (6). These results show that it is possible to improve colonization through genetic engineering (6).Efficient colo...

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“…To measure motility, semisolid (0.35% agar) agar plates containing King B medium diluted 1:20 were used (4). Growth in competition in SSM was carried out as described by Dekkers et al (27).…”

Section: Methodsmentioning

confidence: 99%

A site-specific recombinase is required for competitive root colonization by Pseudomonas fluorescens WCS365

Dekkers

Phoelich

Fits

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

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129

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A colonization mutant of the efficient rootcolonizing biocontrol strain Pseudomonas fluorescens WCS365 is described that is impaired in competitive root-tip colonization of gnotobiotically grown potato, radish, wheat, and tomato, indicating a broad host range mutation. The colonization of the mutant is also impaired when studied in potting soil, suggesting that the defective gene also plays a role under more natural conditions. A DNA fragment that is able to complement the mutation for colonization revealed a multicistronic transcription unit composed of at least six ORFs with similarity to lppL, lysA, dapF, orf235͞233, xerC͞sss, and the largely incomplete orf238. The transposon insertion in PCL1233 appeared to be present in the orf235͞233 homologue, designated orf240. Introduction of a mutation in the xerC͞sss homologue revealed that the xerC͞sss gene homologue rather than orf240 is crucial for colonization. xerC in Escherichia coli and sss in Pseudomonas aeruginosa encode proteins that belong to the integrase family of site-specific recombinases, which play a role in phase variation caused by DNA rearrangements. The function of the xerC͞sss homologue in colonization is discussed in terms of genetic rearrangements involved in the generation of different phenotypes, thereby allowing a bacterial population to occupy various habitats. Mutant PCL1233 is assumed to be locked in a phenotype that is not well suited to compete for colonization in the rhizosphere. Thus we show the importance of phase variation in microbe-plant interactions.The use of microorganisms, including fluorescent Pseudomonas spp., to protect plants against soil-borne diseases is an alternative for the use of chemical pesticides. The biocontrol activity of these strains usually results from the production of one or more antifungal factors. The application of fluorescent Pseudomonas spp. and other plant-growth-promoting rhizobacteria is hampered by inconsistency of performance in the field (1, 2). Although the mechanisms underlying biocontrol are complex and diverse, the need to bring the plant-growthpromoting rhizobacteria cells and their antifungal factors to the right sites at the right time is universal. The importance of this process, designated as root colonization, is underscored in two studies. Schippers et al. (1) showed that inadequate colonization leads to decreased biocontrol activity, and Bull et al. (3) reported an inverse relation between the number of bacteria present on the wheat root and the number of take-all lesions seen on the plant. For these and other reasons, root colonization is often considered the limiting factor for biocontrol in the rhizosphere (1, 2).Two approaches were used in our laboratory to identify traits involved in root colonization. The first approach is to guess which traits are involved in colonization, isolate mutants in these traits, and then test these mutants for colonization in competition with the parental strain. With this approach, motility (4) and synthesis of the O-antigen of lipopolysa...

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A Two-Component System Plays an Important Role in the Root-Colonizing Ability of Pseudomonas fluorescens Strain WCS365

Cited by 106 publications

References 58 publications

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

Generation of Enhanced Competitive Root-Tip-Colonizing Pseudomonas Bacteria through Accelerated Evolution

A site-specific recombinase is required for competitive root colonization by Pseudomonas fluorescens WCS365

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