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Costa-Gutierrez SB, Raimondo EE, Vincent PA, de Cristóbal RE. Importance of biofilm formation for promoting plant growth under salt stress in Pseudomonas putida KT2440. J Basic Microbiol 2023; 63:1219-1232. [PMID: 37537345 DOI: 10.1002/jobm.202300215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/20/2023] [Accepted: 07/12/2023] [Indexed: 08/05/2023]
Abstract
An underutilized experimental design was employed to isolate adapted mutants of the model bacterium Pseudomonas putida KT2440. The design involved subjecting a random pool of mini-Tn5 mutants of P. putida KT2440 to multiple rounds of selection in the rhizosphere of soybean plants irrigated with a NaCl solution. The isolated adapted mutants, referred to as MutAd, exhibited a mutation in the gene responsible for encoding the membrane-binding protein LapA, which plays a role in the initial stages of biofilm formation on abiotic surfaces. Two MutAd bacteria, MutAd160 and MutAd185, along with a lapA deletion mutant, were selected for further investigation to examine the impact of this gene on salt tolerance, rhizosphere fitness, production of extracellular polymeric substances (EPS), and promotion of plant growth. Despite the mutants' inability to form biofilms, they were able to attach to soybean seeds and roots. The MutAd bacteria demonstrated an elevated production of EPS when cultivated under saline conditions, which likely compensated for the absence of biofilm formation. MutAd185 bacteria exhibited enhanced root attachment and promoted the growth of soybean plants in slightly saline soils. The proposed experimental design holds promise for expediting bacterial adaptation to the rhizosphere of plants under specific environmental conditions, identifying genetic mutations that enhance bacterial fitness in those conditions, and thereby increasing their capacity to promote plant growth.
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Affiliation(s)
- Stefanie Bernardette Costa-Gutierrez
- Instituto Superior de Investigaciones Biológicas (INSIBIO, CONICET-UNT) e Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Miguel de Tucumán, Tucumán, Argentina
| | - Enzo Emanuel Raimondo
- Planta Piloto de Procesos Industriales Microbiológicos (PROIMI-CONICET), Avenida Belgrano y Pasaje Caseros, San Miguel de Tucumán, Tucumán, Argentina
- Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Miguel de Tucumán, Tucumán, Argentina
| | - Paula Andrea Vincent
- Instituto Superior de Investigaciones Biológicas (INSIBIO, CONICET-UNT) e Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Miguel de Tucumán, Tucumán, Argentina
| | - Ricardo Ezequiel de Cristóbal
- Instituto Superior de Investigaciones Biológicas (INSIBIO, CONICET-UNT) e Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Miguel de Tucumán, Tucumán, Argentina
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Afordoanyi DM, Diabankana RGC, Komissarov EN, Kuchaev ES, Validov SZ. Characterization of a Novel Bacillus glycinifermentans Strain MGMM1 Based on Full Genome Analysis and Phenotypic Properties for Biotechnological Applications. Microorganisms 2023; 11:1410. [PMID: 37374912 DOI: 10.3390/microorganisms11061410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 05/18/2023] [Accepted: 05/24/2023] [Indexed: 06/29/2023] Open
Abstract
Bacillus species have gained much attention based on their phenotypic characteristics and their genetic architecture as biological control agents and plant growth-promotor with bioremediation potential. In this study, we analyzed the whole genome of a novel strain, Bacillus glycinifermentans MGMM1, isolated from the rhizosphere of a weed plant (Senna occidentalis) and assayed its phenotypic characteristics, as well as antifungal and biocontrol ability. The whole genome analysis of MGMM1 identified 4259 putative coding sequences, with an encoding density of 95.75% attributed to biological functions, including genes involved in stimulating plant growth, such as acetolactate synthase, alsS, and genes involved in the resistance to heavy metal antimony (arsB and arsC). AntiSMASH revealed the presence of biosynthetic gene clusters plipastatin, fengycin, laterocidine, geobacillin II, lichenysin, butirosin A and schizokinen. Tests in vitro confirmed that MGMM1 exhibited antifungal activity against Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407, Alternaria alternata, F. graminearum and F. spp. and produce protease, lipase amylase and cellulase. Bacillus glycinifermentans MGMM1 demonstrated proteolytic (4.82 ± 1.04 U/mL), amylolytic (0.84 ± 0.05 U/mL) and cellulosic (0.35 ± 0.02 U/mL) enzymatic activities, as well as indole-3-acetic acid production (48.96 ± 1.43 μg/mL). Moreover, the probiotic strain MGMM1 demonstrated a high biocontrol potential of inhibiting (up to 51.45 ± 8.08%) the development of tomato disease caused by Forl ZUM2407. These results suggest that B. glycinifermentans MGMM1 has significant potential as a biocontrol, plant growth-promoting agent in agriculture.
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Affiliation(s)
- Daniel Mawuena Afordoanyi
- Laboratory of Molecular Genetics and Microbiology Methods, Kazan Scientific Center of Russian Academy of Sciences, 420111 Kazan, Russia
- Tatar Scientific Research Institute of Agricultural Chemistry and Soil Science, FRC Kazan Scientific Center, Russian Academy of Sciences, 420111 Kazan, Russia
| | - Roderic Gilles Claret Diabankana
- Laboratory of Molecular Genetics and Microbiology Methods, Kazan Scientific Center of Russian Academy of Sciences, 420111 Kazan, Russia
| | - Ernest Nailevich Komissarov
- Laboratory of Molecular Genetics and Microbiology Methods, Kazan Scientific Center of Russian Academy of Sciences, 420111 Kazan, Russia
| | - Evgenii Sergeyevich Kuchaev
- Laboratory of Molecular Genetics and Microbiology Methods, Kazan Scientific Center of Russian Academy of Sciences, 420111 Kazan, Russia
| | - Shamil Zavdatovich Validov
- Laboratory of Molecular Genetics and Microbiology Methods, Kazan Scientific Center of Russian Academy of Sciences, 420111 Kazan, Russia
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Tovi N, Orevi T, Grinberg M, Kashtan N, Hadar Y, Minz D. Pairwise Interactions of Three Related Pseudomonas Species in Plant Roots and Inert Surfaces. Front Microbiol 2021; 12:666522. [PMID: 34335497 PMCID: PMC8320352 DOI: 10.3389/fmicb.2021.666522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
Bacteria are social organisms that interact extensively within and between species while responding to external stimuli from their environments. Designing synthetic microbial communities can enable efficient and beneficial microbiome implementation in many areas. However, in order to design an efficient community, one must consider the interactions between their members. Using a reductionist approach, we examined pairwise interactions of three related Pseudomonas species in various microenvironments including plant roots and inert surfaces. Our results show that the step between monoculture and co-culture is already very complex. Monoculture root colonization patterns demonstrate that each isolate occupied a particular location on wheat roots, such as root tip, distance from the tip, or scattered along the root. However, pairwise colonization outcomes on the root did not follow the bacterial behavior in monoculture, suggesting various interaction patterns. In addition, we show that interspecies interactions on a microscale on inert surface take part in co-culture colonization and that the interactions are affected by the presence of root extracts and depend on its source. The understanding of interrelationships on the root may contribute to future attempts to manipulate and improve bacterial colonization and to intervene with root microbiomes to construct and design effective synthetic microbial consortia.
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Affiliation(s)
- Nesli Tovi
- Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization - Volcani Center, Rishon LeZion, Israel.,Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Tomer Orevi
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Maor Grinberg
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Nadav Kashtan
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Yitzhak Hadar
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Dror Minz
- Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization - Volcani Center, Rishon LeZion, Israel
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Perera M, Wijayarathna D, Wijesundera S, Chinthaka M, Seneviratne G, Jayasena S. Biofilm mediated synergistic degradation of hexadecane by a naturally formed community comprising Aspergillus flavus complex and Bacillus cereus group. BMC Microbiol 2019; 19:84. [PMID: 31035915 PMCID: PMC6489202 DOI: 10.1186/s12866-019-1460-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 04/17/2019] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The hydrophobic nature of hydrocarbons make them less bioavailable to microbes, generally leading to low efficiency in biodegradation. Current bioremediation strategies for hydrocarbon contamination, uses induced mixed microbial cultures. This in-vitro study demonstrates the utilization of naturally occurring communities in suitable habitats for achieving highly efficient, synergistic degradation of hydrocarbons in a simple community structure without additives. METHODS Enrichment media supplemented with 1% (7652.53 mg/L) hexadecane (HXD) as the sole carbon source were inoculated with samples of soil with waste polythene, collected from a municipal landfill in order to isolate microbial communities. Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed on HXD grown co-cultures and individual counterparts after 14 days incubation and percentage degradation was calculated. Microbes were identified using 16S rRNA gene and Internal Transcribed Spacer region sequencing. Biofilm formation was confirmed through scanning electron microscopy, in the most efficient community. RESULTS Three mixed communities (C1, C2 and C3) that demonstrated efficient visual disintegration of the HXD layer in the static liquid cultures were isolated. The C1 community showed the highest activity, degrading > 99% HXD within 14 days. C1 comprised of a single fungus and a bacterium and they were identified as a Bacillus sp. MM1 and an Apsergillus sp. MM1. The co-culture and individual counterparts of the C1 community were assayed for HXD degradation by GC-MS. Degradation by the fungal and bacterial monocultures were 52.92 ± 8.81% and 9.62 ± 0.71% respectively, compared to 99.42 ± 0.38% by the co-culture in 14 days. This proved the synergistic behavior of the community. Further, this community demonstrated the formation of a biofilm in oil-water interface in the liquid medium. This was evidenced from scanning electron microscopy (SEM) showing the Bacillus cells attached on to Aspergillus mycelia. CONCLUSIONS This study demonstrates the utilization of naturally formed fungal-bacterial communities for enhanced biodegradation of hydrocarbons such as hexadecane and reports for the first time, synergistic degradation of hexadecane through biofilm formation, by a community comprising of Bacillus cereus group and Aspergillus flavus complex.
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Affiliation(s)
- Madushika Perera
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Colombo 08, Sri Lanka
| | | | - Sulochana Wijesundera
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Colombo 08, Sri Lanka
| | - Manoj Chinthaka
- Department of Chemistry, Faculty of Applied Sciences, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Gamini Seneviratne
- National Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka
| | - Sharmila Jayasena
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Colombo 08, Sri Lanka.
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Convergent gain and loss of genomic islands drive lifestyle changes in plant-associated Pseudomonas. ISME JOURNAL 2019; 13:1575-1588. [PMID: 30787396 DOI: 10.1038/s41396-019-0372-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/04/2019] [Accepted: 01/31/2019] [Indexed: 01/07/2023]
Abstract
Host-associated bacteria can have both beneficial and detrimental effects on host health. While some of the molecular mechanisms that determine these outcomes are known, little is known about the evolutionary histories of pathogenic or mutualistic lifestyles. Using the model plant Arabidopsis, we found that closely related strains within the Pseudomonas fluorescens species complex promote plant growth and occasionally cause disease. To elucidate the genetic basis of the transition between commensalism and pathogenesis, we developed a computational pipeline and identified genomic islands that correlate with outcomes for plant health. One island containing genes for lipopeptide biosynthesis and quorum-sensing is required for pathogenesis. Conservation of the quorum-sensing machinery in this island allows pathogenic strains to eavesdrop on quorum signals in the environment and coordinate pathogenic behavior. We found that genomic loci associated with both pathogenic and commensal lifestyles were convergently gained and lost in multiple lineages through homologous recombination, possibly constituting an early step in the differentiation of pathogenic and commensal lifestyles. Collectively this work provides novel insights into the evolution of commensal and pathogenic lifestyles within a single clade of host-associated bacteria.
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Kim YC, Anderson AJ. Rhizosphere pseudomonads as probiotics improving plant health. MOLECULAR PLANT PATHOLOGY 2018; 19:2349-2359. [PMID: 29676842 PMCID: PMC6638116 DOI: 10.1111/mpp.12693] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 04/08/2018] [Accepted: 04/18/2018] [Indexed: 05/25/2023]
Abstract
Many root-colonizing microbes are multifaceted in traits that improve plant health. Although isolates designated as biological control agents directly reduce pathogen growth, many exert additional beneficial features that parallel changes induced in animal and other hosts by health-promoting microbes termed probiotics. Both animal and plant probiotics cause direct antagonism of pathogens and induce systemic immunity in the host to pathogens and other stresses. They also alter host development and improve host nutrition. The probiotic root-colonizing pseudomonads are generalists in terms of plant hosts, soil habitats and the array of stress responses that are ameliorated in the plant. This article illustrates how the probiotic pseudomonads, nurtured by the carbon (C) and nitrogen (N) sources released by the plant in root exudates, form protective biofilms on the root surface and produce the metabolites or enzymes to boost plant health. The findings reveal the multifunctional nature of many of the microbial metabolites in the plant-probiotic interplay. The beneficial effects of probiotics on plant function can contribute to sustainable yield and quality in agricultural production.
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Affiliation(s)
- Young Cheol Kim
- Department of Applied Biology, College of Agriculture and Life SciencesChonnam National UniversityGwangju 61186South Korea
| | - Anne J. Anderson
- Department of Biological EngineeringUtah State UniversityLoganUT 84322‐4105USA
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Abstract
Microbes in nature often live in unfavorable conditions. To survive, they have to occupy niches close to food sources and efficiently utilize nutrients that are often present in very low concentrations. Moreover, they have to possess an arsenal of attack and defense mechanisms against competing bacteria. In this review, we will discuss strategies used by microbes to compete with each other in the rhizosphere and on fruits, with a focus on mechanisms of inter- and intra-species antagonism. Special attention will be paid to the recently discovered roles of volatile organic compounds. Several microbes with proven capabilities in the art of warfare are being applied in products used for the biological control of plant diseases, including post-harvest control of fruits and vegetables.
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Affiliation(s)
- Ben Lugtenberg
- Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, Netherlands
| | - Daniel E Rozen
- Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, Netherlands
| | - Faina Kamilova
- Koppert Biological Systems, Veilingweg 14, PO Box 155, 2650 AD Berkel en Rodenrijs, Netherlands
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Tikhonovich IA, Andronov EE, Borisov AY, Dolgikh EA, Zhernakov AI, Zhukov VA, Provorov NA, Roumiantseva ML, Simarov BV. The principle of genome complementarity in the enhancement of plant adaptive capacities. RUSS J GENET+ 2015. [DOI: 10.1134/s1022795415090124] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Prieto P, Schilirò E, Maldonado-González MM, Valderrama R, Barroso-Albarracín JB, Mercado-Blanco J. Root hairs play a key role in the endophytic colonization of olive roots by Pseudomonas spp. with biocontrol activity. MICROBIAL ECOLOGY 2011; 62:435-45. [PMID: 21347721 PMCID: PMC3155037 DOI: 10.1007/s00248-011-9827-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 02/08/2011] [Indexed: 05/05/2023]
Abstract
The use of indigenous bacterial root endophytes with biocontrol activity against soil-borne phytopathogens is an environmentally-friendly and ecologically-efficient action within an integrated disease management framework. The earliest steps of olive root colonization by Pseudomonas fluorescens PICF7 and Pseudomonas putida PICP2, effective biocontrol agents (BCAs) against Verticillium wilt of olive (Olea europaea L.) caused by the fungus Verticillium dahliae Kleb., are here described. A gnotobiotic study system using in vitro propagated olive plants, differential fluorescent-protein tagging of bacteria, and confocal laser scanning microscopy analysis have been successfully used to examine olive roots-Pseudomonas spp. interactions at the single-cell level. In vivo simultaneous visualization of PICF7 and PICP2 cells on/in root tissues enabled to discard competition between the two bacterial strains during root colonization. Results demonstrated that both BCAs are able to endophytically colonized olive root tissues. Moreover, results suggest a pivotal role of root hairs in root colonization by both biocontrol Pseudomonas spp. However, colonization of root hairs appeared to be a highly specific event, and only a very low number of root hairs were effectively colonized by introduced bacteria. Strains PICF7 and PICP2 can simultaneously colonize the same root hair, demonstrating that early colonization of a given root hair by one strain did not hinder subsequent attachment and penetration by the other. Since many environmental factors can affect the number, anatomy, development, and physiology of root hairs, colonization competence and biocontrol effectiveness of BCAs may be greatly influenced by root hair's fitness. Finally, the in vitro study system here reported has shown to be a suitable tool to investigate colonization processes of woody plant roots by microorganisms with biocontrol potential.
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Affiliation(s)
- Pilar Prieto
- Departamento de Mejora Genética, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas (CSIC), Alameda del Obispo s/n, Apdo. 4084, 14080 Córdoba, Spain
| | - Elisabetta Schilirò
- Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas (CSIC), Alameda del Obispo s/n, Apdo. 4084, 14080 Córdoba, Spain
| | - María Mercedes Maldonado-González
- Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas (CSIC), Alameda del Obispo s/n, Apdo. 4084, 14080 Córdoba, Spain
| | - Raquel Valderrama
- Departamento de Biología Experimental, Universidad de Jaén, 23071 Jaén, Spain
| | | | - Jesús Mercado-Blanco
- Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas (CSIC), Alameda del Obispo s/n, Apdo. 4084, 14080 Córdoba, Spain
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Lebeau T. Bioaugmentation for In Situ Soil Remediation: How to Ensure the Success of Such a Process. SOIL BIOLOGY 2011. [DOI: 10.1007/978-3-642-19769-7_7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Dennis PG, Miller AJ, Hirsch PR. Are root exudates more important than other sources of rhizodeposits in structuring rhizosphere bacterial communities? FEMS Microbiol Ecol 2010; 72:313-27. [PMID: 20370828 DOI: 10.1111/j.1574-6941.2010.00860.x] [Citation(s) in RCA: 350] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
This review evaluates the importance of root exudates in determining rhizosphere bacterial community structure. We present evidence that indicates that: (1) the direct influence of root exudates on rhizosphere bacterial communities is limited to small spatiotemporal windows related to root apices; (2) upon rapid assimilation by microorganisms, root exudates are modified, independent of plant influences, before rerelease into the rhizosphere by the microorganisms themselves--thus, at short distances from root apices, rhizosphere carbon pools are unlikely to be dominated by root exudates; and (3) many of the major compounds found in root exudates are ubiquitous in the rhizosphere as they are found in other pools of rhizodeposits and in microbial exudates. Following this argument, we suggest that the importance of root exudates in structuring rhizosphere bacterial communities needs to be considered in the context of the wider contribution of other rhizosphere carbon pools. Finally, we discuss the implications of rhizosphere bacterial distribution trends for the development of effective strategies to manage beneficial plant-microorganism interactions.
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Couillerot O, Prigent-Combaret C, Caballero-Mellado J, Moënne-Loccoz Y. Pseudomonas fluorescensand closely-related fluorescent pseudomonads as biocontrol agents of soil-borne phytopathogens. Lett Appl Microbiol 2009; 48:505-12. [DOI: 10.1111/j.1472-765x.2009.02566.x] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Transcriptional organization of the region encoding the synthesis of the flagellar filament in Pseudomonas fluorescens. J Bacteriol 2008; 190:4106-9. [PMID: 18375555 DOI: 10.1128/jb.00178-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas fluorescens F113 is motile by means of type b flagella. Analysis of the region encoding the synthesis of the flagellar filament has shown a transcriptional organization different from that of type a flagella. Additionally to the promoters driving fliC, fliD, and fleQ expression, we have found promoters upstream of the flaG gene and the fliST operon. These promoters were functional in vivo. Both promoters have been mapped and appear to be dependent on the vegetative sigma factor and independent of FleQ, the master regulator of flagellum synthesis.
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14
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Saumaa S, Tover A, Tark M, Tegova R, Kivisaar M. Oxidative DNA damage defense systems in avoidance of stationary-phase mutagenesis in Pseudomonas putida. J Bacteriol 2007; 189:5504-14. [PMID: 17545288 PMCID: PMC1951809 DOI: 10.1128/jb.00518-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Oxidative damage of DNA is a source of mutation in living cells. Although all organisms have evolved mechanisms of defense against oxidative damage, little is known about these mechanisms in nonenteric bacteria, including pseudomonads. Here we have studied the involvement of oxidized guanine (GO) repair enzymes and DNA-protecting enzyme Dps in the avoidance of mutations in starving Pseudomonas putida. Additionally, we examined possible connections between the oxidative damage of DNA and involvement of the error-prone DNA polymerase (Pol)V homologue RulAB in stationary-phase mutagenesis in P. putida. Our results demonstrated that the GO repair enzymes MutY, MutM, and MutT are involved in the prevention of base substitution mutations in carbon-starved P. putida. Interestingly, the antimutator effect of MutT was dependent on the growth phase of bacteria. Although the lack of MutT caused a strong mutator phenotype under carbon starvation conditions for bacteria, only a twofold increased effect on the frequency of mutations was observed for growing bacteria. This indicates that MutT has a backup system which efficiently complements the absence of this enzyme in actively growing cells. The knockout of MutM affected only the spectrum of mutations but did not change mutation frequency. Dps is known to protect DNA from oxidative damage. We found that dps-defective P. putida cells were more sensitive to sudden exposure to hydrogen peroxide than wild-type cells. At the same time, the absence of Dps did not affect the accumulation of mutations in populations of starved bacteria. Thus, it is possible that the protective role of Dps becomes essential for genome integrity only when bacteria are exposed to exogenous agents that lead to oxidative DNA damage but not under physiological conditions. Introduction of the Y family DNA polymerase PolV homologue rulAB into P. putida increased the proportion of A-to-C and A-to-G base substitutions among mutations, which occurred under starvation conditions. Since PolV is known to perform translesion synthesis past damaged bases in DNA (e.g., some oxidized forms of adenine), our results may imply that adenine oxidation products are also an important source of mutation in starving bacteria.
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Affiliation(s)
- Signe Saumaa
- Department of Genetics, Institute of Molecular and Cell Biology, Tartu University and Estonian Biocentre, 23 Riia Street, 51010 Tartu, Estonia
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15
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Validov S, Kamilova F, Qi S, Stephan D, Wang JJ, Makarova N, Lugtenberg B. Selection of bacteria able to control Fusarium oxysporum f. sp. radicis-lycopersici in stonewool substrate. J Appl Microbiol 2007; 102:461-71. [PMID: 17241352 DOI: 10.1111/j.1365-2672.2006.03083.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS Tomato foot and root rot (TFRR), caused by Fusariumoxysporum f. sp. radicis-lycopersici (Forl), is an economically important disease of tomato. The aim of this study was to develop an efficient protocol for the isolation of bacteria, which controls TFRR based on selection of enhanced competitive root-colonizing bacteria from total rhizosphere soil samples. METHODS AND RESULTS A total of 216 potentially enhanced bacterial strains were isolated from 17 rhizosphere soil samples after applying a procedure to enrich for enhanced root tip colonizers. Amplified ribosomal DNA restriction analysis, in combination with determination of phenotypic traits, was introduced to evaluate the presence of siblings. One hundred sixteen strains were discarded as siblings. Thirty-eight strains were discarded as potential pathogens based on the sequence of their 16S rDNA. Of the remaining strains, 24 performed equally well or better than the good root colonizer Pseudomonas fluorescens WCS365 in a competitive tomato root tip colonization assay. Finally, these enhanced colonizers were tested for their ability to control TFRR in stonewool, which resulted in seven new biocontrol strains. CONCLUSIONS The new biocontrol strains, six Gram-negative and one Gram-positive bacteria, were identified as three Pseudomonas putida strains and one strain each of Delftia tsuruhatensis, Pseudomonas chlororaphis, Pseudomonas rhodesiae and Paenibacillus amylolyticus. SIGNIFICANCE AND IMPACT OF THE STUDY We describe a fast method for the isolation of bacteria able to suppress TFRR in stonewool, an industrial plant growth substrate. The procedure minimizes the laborious screens that are a common feature in the isolation of biocontrol strains.
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Affiliation(s)
- S Validov
- Clusius Laboratory, Institute of Biology, Leiden University, Leiden, Netherlands.
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de Weert S, Dekkers LC, Bitter W, Tuinman S, Wijfjes AHM, van Boxtel R, Lugtenberg BJJ. The two-component colR/S system of Pseudomonas fluorescens WCS365 plays a role in rhizosphere competence through maintaining the structure and function of the outer membrane. FEMS Microbiol Ecol 2006; 58:205-13. [PMID: 17064262 DOI: 10.1111/j.1574-6941.2006.00158.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Pseudomonas fluorescens strain PCL1210, a competitive tomato root tip colonization mutant of the efficient root colonizing wild type strain WCS365, is impaired in the two-component sensor-response regulator system ColR/ColS. Here we show that a putative methyltransferase/wapQ operon is located downstream of colR/colS and that this operon is regulated by ColR/ColS. Since wapQ encodes a putative lipopolysaccharide (LPS) phosphatase, the possibility was studied that the integrity of the outer membrane of PCL1210 was altered. Indeed, it was shown that mutant PCL1210 is more resistant to various chemically unrelated antibiotics which have to pass the outer membrane for their action. In contrast, the mutant is more sensitive to the LPS-binding antibiotic polymyxin B. Mutant PCL1210 loses growth in competition with its wild type when grown in tomato root exudate. Mutants in the methyltransferase/wapQ operon are also altered in their outer membrane permeability and are defective in competitive tomato root tip colonization. A model for the altered outer membrane of PCL1210 is discussed.
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Affiliation(s)
- Sandra de Weert
- Institute of Biology, Leiden University, AL Leiden, The Netherlands.
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Martínez-Granero F, Rivilla R, Martín M. Rhizosphere selection of highly motile phenotypic variants of Pseudomonas fluorescens with enhanced competitive colonization ability. Appl Environ Microbiol 2006; 72:3429-34. [PMID: 16672487 PMCID: PMC1472367 DOI: 10.1128/aem.72.5.3429-3434.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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.
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Affiliation(s)
- Francisco Martínez-Granero
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, c/Darwin 2, 28049 Madrid, Spain
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Kamilova F, Validov S, Azarova T, Mulders I, Lugtenberg B. Enrichment for enhanced competitive plant root tip colonizers selects for a new class of biocontrol bacteria. Environ Microbiol 2006; 7:1809-17. [PMID: 16232295 DOI: 10.1111/j.1462-2920.2005.00889.x] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Our group studies tomato foot and root rot, a plant disease caused by the fungus Forl (Fusarium oxysporum f.sp. radicis-lycopersici ). Several bacteria have been described to be able to control the disease, using different mechanisms. Here we describe a method that enables us to select, after application of a crude rhizobacterial mixture on a sterile seedling, those strains that reach the root tip faster than our best tomato root colonizer tested so far, the Pseudomonas fluorescens biocontrol strain WCS365. Of the five tested new isolates, four appeared to be able to reduce the number of diseased plants. Analysis of one of these strains, P. fluorescens PCL1751, suggests that it controls the disease through the mechanism 'competition for nutrients and niches', a mechanism novel for biocontrol bacteria. Moreover, this is the first report describing a method to enrich for biocontrol strains from a crude mixture of rhizobacteria. Another advantage of the method is that four out of five strains do not produce antifungal metabolites, which is preferential for registration as a commercial product.
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Affiliation(s)
- Faina Kamilova
- Institute Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, the Netherlands.
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Davidsen T, Bjørås M, Seeberg EC, Tønjum T. Antimutator role of DNA glycosylase MutY in pathogenic Neisseria species. J Bacteriol 2005; 187:2801-9. [PMID: 15805527 PMCID: PMC1070393 DOI: 10.1128/jb.187.8.2801-2809.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Genome alterations due to horizontal gene transfer and stress constantly generate strain on the gene pool of Neisseria meningitidis, the causative agent of meningococcal (MC) disease. The DNA glycosylase MutY of the base excision repair pathway is involved in the protection against oxidative stress. MC MutY expressed in Escherichia coli exhibited base excision activity towards DNA substrates containing A:7,8-dihydro-8-oxo-2'-deoxyguanosine and A:C mismatches. Expression in E. coli fully suppressed the elevated spontaneous mutation rate found in the E. coli mutY mutant. An assessment of MutY activity in lysates of neisserial wild-type and mutY mutant strains showed that both MC and gonococcal (GC) MutY is expressed and active in vivo. Strikingly, MC and GC mutY mutants exhibited 60- to 140-fold and 20-fold increases in mutation rates, respectively, compared to the wild-type strains. Moreover, the differences in transitions and transversions in rpoB conferring rifampin resistance observed with the wild type and mutants demonstrated that the neisserial MutY enzyme works in preventing GC-->AT transversions. These findings are important in the context of models linking mutator phenotypes of disease isolates to microbial fitness.
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Affiliation(s)
- T Davidsen
- Centre for Molecular Biology and Neuroscience and Institute of Microbiology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
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