Editorial

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2 pages, 188 KiB

Open AccessEditorial

Editorial for Special Issue “Interactions between Plant Beneficial Pseudomonas spp. and Their Host”

by Martin Filion

Microorganisms 2023, 11(10), 2591; https://doi.org/10.3390/microorganisms11102591 - 20 Oct 2023

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Abstract

Plant-beneficial Pseudomonas spp [...] Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

Research

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15 pages, 3636 KiB

Open AccessArticle

Identification and Characterization of Bacteria-Derived Antibiotics for the Biological Control of Pea Aphanomyces Root Rot

by Xiao Lai, Dhirendra Niroula, Mary Burrows, Xiaogang Wu and Qing Yan

Microorganisms 2022, 10(8), 1596; https://doi.org/10.3390/microorganisms10081596 - 08 Aug 2022

Cited by 3 | Viewed by 1757

Abstract

Antibiosis has been proposed to contribute to the beneficial bacteria-mediated biocontrol against pea Aphanomyces root rot caused by the oomycete pathogen Aphanomyces euteiches. However, the antibiotics required for disease suppression remain unknown. In this study, we found that the wild type strains [...] Read more.

Antibiosis has been proposed to contribute to the beneficial bacteria-mediated biocontrol against pea Aphanomyces root rot caused by the oomycete pathogen Aphanomyces euteiches. However, the antibiotics required for disease suppression remain unknown. In this study, we found that the wild type strains of Pseudomonas protegens Pf-5 and Pseudomonas fluorescens 2P24, but not their mutants that lack 2,4-diacetylphloroglucinol, strongly inhibited A. euteiches on culture plates. Purified 2,4-diacetylphloroglucinol compound caused extensive hyphal branching and stunted hyphal growth of A. euteiches. Using a GFP-based transcriptional reporter assay, we found that expression of the 2,4-diacetylphloroglucinol biosynthesis gene phlA_Pf-5 is activated by germinating pea seeds. The 2,4-diacetylphloroglucinol producing Pf-5 derivative, but not its 2,4-diacetylphloroglucinol non-producing mutant, reduced disease severity caused by A. euteiches on pea plants in greenhouse conditions. This is the first report that 2,4-diacetylphloroglucinol produced by strains of Pseudomonas species plays an important role in the biocontrol of pea Aphanomyces root rot. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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11 pages, 1207 KiB

Open AccessArticle

Bacterial Volatiles Known to Inhibit Phytophthora infestans Are Emitted on Potato Leaves by Pseudomonas Strains

by Aurélie Gfeller, Pascal Fuchsmann, Mout De Vrieze, Katia Gindro and Laure Weisskopf

Microorganisms 2022, 10(8), 1510; https://doi.org/10.3390/microorganisms10081510 - 26 Jul 2022

Cited by 8 | Viewed by 1478

Abstract

Bacterial volatiles play important roles in mediating beneficial interactions between plants and their associated microbiota. Despite their relevance, bacterial volatiles are mostly studied under laboratory conditions, although these strongly differ from the natural environment bacteria encounter when colonizing plant roots or shoots. In [...] Read more.

Bacterial volatiles play important roles in mediating beneficial interactions between plants and their associated microbiota. Despite their relevance, bacterial volatiles are mostly studied under laboratory conditions, although these strongly differ from the natural environment bacteria encounter when colonizing plant roots or shoots. In this work, we ask the question whether plant-associated bacteria also emit bioactive volatiles when growing on plant leaves rather than on artificial media. Using four potato-associated Pseudomonas, we demonstrate that potato leaves offer sufficient nutrients for the four strains to grow and emit volatiles, among which 1-undecene and Sulfur compounds have previously demonstrated the ability to inhibit the development of the oomycete Phytophthora infestans, the causative agent of potato late blight. Our results bring the proof of concept that bacterial volatiles with known plant health-promoting properties can be emitted on the surface of leaves and warrant further studies to test the bacterial emission of bioactive volatiles in greenhouse and field-grown plants. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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11 pages, 4328 KiB

Open AccessArticle

Effects of Humic Substances on the Growth of Pseudomonas plecoglossicida 2,4-D and Wheat Plants Inoculated with This Strain

by Arina Feoktistova, Margarita Bakaeva, Maxim Timergalin, Darya Chetverikova, Aliya Kendjieva, Timur Rameev, Gaisar Hkudaygulov, Aleksey Nazarov, Guzel Kudoyarova and Sergey Chetverikov

Microorganisms 2022, 10(5), 1066; https://doi.org/10.3390/microorganisms10051066 - 22 May 2022

Cited by 9 | Viewed by 1832

Abstract

Both rhizosphere bacteria and humic substances (HSs) can promote plant growth when applied individually and even greater effects of their combination have been demonstrated. We aimed to elucidate the relative importance of the stimulating effects of HSs on bacterial growth and the effects [...] Read more.

Both rhizosphere bacteria and humic substances (HSs) can promote plant growth when applied individually and even greater effects of their combination have been demonstrated. We aimed to elucidate the relative importance of the stimulating effects of HSs on bacterial growth and the effects of the combination of bacteria and HSs on plants themselves. The effects of humic (HA) and fulvic acids (FA) (components of humic substances) on the growth of Pseudomonas plecoglossicida 2,4-D in vitro were studied. We also studied the effects of this bacterial strain and HSs applied individually or in combination on the growth of wheat plants. Although the 2,4-D strain showed low ability to use HSs as the sole source of nutrition, the bacterial growth rate was increased by FA and HA, when other nutrients were available. HSs increased root colonization with bacteria, the effect being greater in the case of HA. The effects on roots and shoots increased when bacteria were associated with HSs. FA+ 2,4-D was more effective in stimulating shoot growth, while HA + 2,4-D was in the case of root growth. The latter effect is likely to be beneficial under edaphic stresses. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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12 pages, 1579 KiB

Open AccessArticle

The Effects of Rhizosphere Inoculation with Pseudomonas mandelii on Formation of Apoplast Barriers, HvPIP2 Aquaporins and Hydraulic Conductance of Barley

by Tatiana Arkhipova, Guzel Sharipova, Guzel Akhiyarova, Ludmila Kuzmina, Ilshat Galin, Elena Martynenko, Oksana Seldimirova, Tatyana Nuzhnaya, Arina Feoktistova, Maxim Timergalin and Guzel Kudoyarova

Microorganisms 2022, 10(5), 935; https://doi.org/10.3390/microorganisms10050935 - 29 Apr 2022

Cited by 14 | Viewed by 1612

Abstract

Pseudomonas mandelii strain IB-Ki14 has recently been shown to strengthen the apoplastic barriers of salt-stressed plants, which prevents the entry of toxic sodium. It was of interest to find out whether the same effect manifests itself in the absence of salinity and how [...] Read more.

Pseudomonas mandelii strain IB-Ki14 has recently been shown to strengthen the apoplastic barriers of salt-stressed plants, which prevents the entry of toxic sodium. It was of interest to find out whether the same effect manifests itself in the absence of salinity and how this affects the hydraulic conductivity of barley plants. Berberine staining confirmed that the bacterial treatment enhanced the deposition of lignin and suberin and formation of Casparian bands in the roots of barley plants. The calculation of hydraulic conductance by relating transpiration to leaf water potential showed that it did not decrease in bacteria-treated plants. We hypothesized that reduced apoplastic conductivity could be compensated by the higher conductivity of the water pathway across the membranes. This assumption was confirmed by the results of the immunolocalization of HvPIP2;5 aquaporins with specific antibodies, showing their increased abundance around the areas of the endodermis and exodermis of bacteria-treated plants. The immunolocalization with antibodies against auxins and abscisic acid revealed elevated levels of these hormones in the roots of plants treated with bacteria. This root accumulation of hormones is likely to be associated with the ability of Pseudomonas mandelii IB-Ki14 to synthesize these hormones. The involvement of abscisic acid in the control of aquaporin abundance and auxins—in the regulation of and formation of apoplast barriers—is discussed. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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17 pages, 3312 KiB

Open AccessArticle

Interplay between Arabidopsis thaliana Genotype, Plant Growth and Rhizosphere Colonization by Phytobeneficial Phenazine-Producing Pseudomonas chlororaphis

by Antoine Zboralski, Hara Saadia, Amy Novinscak and Martin Filion

Microorganisms 2022, 10(3), 660; https://doi.org/10.3390/microorganisms10030660 - 19 Mar 2022

Cited by 3 | Viewed by 2592

Abstract

Rhizosphere colonization by phytobeneficial Pseudomonas spp. is pivotal in triggering their positive effects on plant health. Many Pseudomonas spp. Determinants, involved in rhizosphere colonization, have already been deciphered. However, few studies have explored the role played by specific plant genes in rhizosphere colonization [...] Read more.

Rhizosphere colonization by phytobeneficial Pseudomonas spp. is pivotal in triggering their positive effects on plant health. Many Pseudomonas spp. Determinants, involved in rhizosphere colonization, have already been deciphered. However, few studies have explored the role played by specific plant genes in rhizosphere colonization by these bacteria. Using isogenic Arabidopsis thaliana mutants, we studied the effect of 20 distinct plant genes on rhizosphere colonization by two phenazine-producing P. chlororaphis strains of biocontrol interest, differing in their colonization abilities: DTR133, a strong rhizosphere colonizer and ToZa7, which displays lower rhizocompetence. The investigated plant mutations were related to root exudation, immunity, and root system architecture. Mutations in smb and shv3, both involved in root architecture, were shown to positively affect rhizosphere colonization by ToZa7, but not DTR133. While these strains were not promoting plant growth in wild-type plants, increased plant biomass was measured in inoculated plants lacking fez, wrky70, cbp60g, pft1 and rlp30, genes mostly involved in plant immunity. These results point to an interplay between plant genotype, plant growth and rhizosphere colonization by phytobeneficial Pseudomonas spp. Some of the studied genes could become targets for plant breeding programs to improve plant-beneficial Pseudomonas rhizocompetence and biocontrol efficiency in the field. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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15 pages, 2511 KiB

Open AccessArticle

In Tuber Biocontrol of Potato Late Blight by a Collection of Phenazine-1-Carboxylic Acid-Producing Pseudomonas spp.

by Geneviève Léger, Amy Novinscak, Adrien Biessy, Simon Lamarre and Martin Filion

Microorganisms 2021, 9(12), 2525; https://doi.org/10.3390/microorganisms9122525 - 07 Dec 2021

Cited by 8 | Viewed by 2237

Abstract

Phenazine-1-carboxylic acid (PCA) produced by plant-beneficial Pseudomonas spp. is an antibiotic with antagonistic activities against Phytophthora infestans, the causal agent of potato late blight. In this study, a collection of 23 different PCA-producing Pseudomonas spp. was confronted with P. infestans in potato [...] Read more.

Phenazine-1-carboxylic acid (PCA) produced by plant-beneficial Pseudomonas spp. is an antibiotic with antagonistic activities against Phytophthora infestans, the causal agent of potato late blight. In this study, a collection of 23 different PCA-producing Pseudomonas spp. was confronted with P. infestans in potato tuber bioassays to further understand the interaction existing between biocontrol activity and PCA production. Overall, the 23 strains exhibited different levels of biocontrol activity. In general, P. orientalis and P. yamanorum strains showed strong disease reduction, while P. synxantha strains could not effectively inhibit the pathogen’s growth. No correlation was found between the quantities of PCA produced and biocontrol activity, suggesting that PCA cannot alone explain P. infestans’ growth inhibition by phenazine-producing pseudomonads. Other genetic determinants potentially involved in the biocontrol of P. infestans were identified through genome mining in strains displaying strong biocontrol activity, including siderophores, cyclic lipopeptides and non-ribosomal peptide synthase and polyketide synthase hybrid clusters. This study represents a step forward towards better understanding the biocontrol mechanisms of phenazine-producing Pseudomonas spp. against potato late blight. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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18 pages, 2071 KiB

Open AccessArticle

Phenazine-1-carboxylic Acid Produced by Pseudomonas chlororaphis YL-1 Is Effective against Acidovorax citrulli

by Youzhou Liu, Yaqiu Zhou, Junqing Qiao, Wenjie Yu, Xiayan Pan, Tingting Zhang, Yongfeng Liu and Shi-En Lu

Microorganisms 2021, 9(10), 2012; https://doi.org/10.3390/microorganisms9102012 - 23 Sep 2021

Cited by 5 | Viewed by 2246

Abstract

The bacterial pathogen Acidovorax citrulli causes the destructive fruit blotch (BFB) on cucurbit plants. Pseudomonas chlororaphis YL-1 is a bacterial strain isolated from Mississippi soil and its genome harbors some antimicrobial-related gene clusters, such as phenazine, pyrrolnitrin, and pyoverdine. Here, we evaluated the [...] Read more.

The bacterial pathogen Acidovorax citrulli causes the destructive fruit blotch (BFB) on cucurbit plants. Pseudomonas chlororaphis YL-1 is a bacterial strain isolated from Mississippi soil and its genome harbors some antimicrobial-related gene clusters, such as phenazine, pyrrolnitrin, and pyoverdine. Here, we evaluated the antimicrobial activity of strain YL-1 as compared with its deficient mutants of antimicrobial-related genes, which were obtained using a sacB-based site-specific mutagenesis strategy. We found that only phenazine-deficient mutants ΔphzE and ΔphzF almost lost the inhibitory effects against A. citrulli in LB plates compared with the wild-type strain YL-1, and that the main antibacterial compound produced by strain YL-1 in LB medium was phenazine-1-carboxylic acid (PCA) based on the liquid chromatography-mass spectrometry (LC-MS) analysis. Gene expression analyses revealed that PCA enhanced the accumulation of reactive oxygen species (ROS) and increased the activity of catalase (CAT) in A. citrulli. The inhibition effect of PCA against A. citrulli was lowered by adding exogenous CAT. PCA significantly upregulated the transcript level of katB from 6 to 10 h, which encodes CAT that helps to protect the bacteria against oxidative stress. Collectively, the findings of this research suggest PCA is one of the key antimicrobial metabolites of bacterial strain YL-1, a promising biocontrol agent for disease management of BFB of cucurbit plants. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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15 pages, 1949 KiB

Open AccessArticle

Transcriptome Signatures in Pseudomonas simiae WCS417 Shed Light on Role of Root-Secreted Coumarins in Arabidopsis-Mutualist Communication

by Ke Yu, Ioannis A. Stringlis, Sietske van Bentum, Ronnie de Jonge, Basten L. Snoek, Corné M. J. Pieterse, Peter A. H. M. Bakker and Roeland L. Berendsen

Microorganisms 2021, 9(3), 575; https://doi.org/10.3390/microorganisms9030575 - 11 Mar 2021

Cited by 13 | Viewed by 3930

Abstract

Pseudomonas simiae WCS417 is a root-colonizing bacterium with well-established plant-beneficial effects. Upon colonization of Arabidopsis roots, WCS417 evades local root immune responses while triggering an induced systemic resistance (ISR) in the leaves. The early onset of ISR in roots shows similarities with the [...] Read more.

Pseudomonas simiae WCS417 is a root-colonizing bacterium with well-established plant-beneficial effects. Upon colonization of Arabidopsis roots, WCS417 evades local root immune responses while triggering an induced systemic resistance (ISR) in the leaves. The early onset of ISR in roots shows similarities with the iron deficiency response, as both responses are associated with the production and secretion of coumarins. Coumarins can mobilize iron from the soil environment and have a selective antimicrobial activity that impacts microbiome assembly in the rhizosphere. Being highly coumarin-tolerant, WCS417 induces the secretion of these phenolic compounds, likely to improve its own niche establishment, while providing growth and immunity benefits for the host in return. To investigate the possible signaling function of coumarins in the mutualistic Arabidopsis-WCS417 interaction, we analyzed the transcriptome of WCS417 growing in root exudates of coumarin-producing Arabidopsis Col-0 and the coumarin-biosynthesis mutant f6′h1. We found that coumarins in F6′H1-dependent root exudates significantly affected the expression of 439 bacterial genes (8% of the bacterial genome). Of those, genes with functions related to transport and metabolism of carbohydrates, amino acids, and nucleotides were induced, whereas genes with functions related to cell motility, the bacterial mobilome, and energy production and conversion were repressed. Strikingly, most genes related to flagellar biosynthesis were down-regulated by F6′H1-dependent root exudates and we found that application of selected coumarins reduces bacterial motility. These findings suggest that coumarins’ function in the rhizosphere as semiochemicals in the communication between the roots and WCS417. Collectively, our results provide important novel leads for future functional analysis of molecular processes in the establishment of plant-mutualist interactions. Full article

(This article belongs to the Special Issue Interactions between Plant Beneficial Pseudomonas spp. and Their Host)

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