Special Issue "Symbiotic Plant-Bacterial Endospheric Interactions"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: closed (20 October 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Sharon Lafferty Doty

School of Environmental and Forest Sciences, University of Washington, Seattle, USA
Website | E-Mail
Interests: Symbiosis, plant-microbe interactions, early-successional plant species, N-fixation, plant stress tolerance, inter-kingdom molecular communication

Special Issue Information

Dear Colleagues,

While plant-microbe symbioses, involving root nodules (Rhizobia and Frankia) or the root-soil interface (rhizosphere), have been well-studied, the intimate interaction of the phytobiota, endophytes and epiphytes, with the plant host is a relatively new field of research. Nutrient acquisition, phytohormone production and modulation, antimicrobials and other defense-related compounds, and native and xenobiotic chemical detoxification are all ways in which the phytobiome can impact plant health. These interactions may be essential to how plants in their native environments survive and thrive, especially in challenging environments. This Special Issue highlights recent research on the importance of the phytobiome to plant health and growth, with an emphasis on native plant-microbe interactions.

Prof. Dr. Sharon Lafferty Doty
Guest Editor

Manuscript Submission Information

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Keywords

  • N-fixation
  • non-nodulating
  • non-actinorhizal
  • plant growth-promoting bacteria
  • native associations
  • hostile environments

Published Papers (7 papers)

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Editorial

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Open AccessEditorial Symbiotic Plant-Bacterial Endospheric Interactions
Microorganisms 2018, 6(2), 28; https://doi.org/10.3390/microorganisms6020028
Received: 15 March 2018 / Revised: 15 March 2018 / Accepted: 20 March 2018 / Published: 22 March 2018
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Abstract
While plant-microbe symbioses involving root nodules (Rhizobia and Frankia) or the root-soil interface (rhizosphere) have been well studied, the intimate interaction of microbial endophytes with the plant host is a relatively new field of research.[...] Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)

Research

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Open AccessArticle Fungal Disease Prevention in Seedlings of Rice (Oryza sativa) and Other Grasses by Growth-Promoting Seed-Associated Endophytic Bacteria from Invasive Phragmites australis
Microorganisms 2018, 6(1), 21; https://doi.org/10.3390/microorganisms6010021
Received: 26 January 2018 / Revised: 28 February 2018 / Accepted: 2 March 2018 / Published: 8 March 2018
Cited by 3 | PDF Full-text (10466 KB) | HTML Full-text | XML Full-text
Abstract
Non-cultivated plants carry microbial endophytes that may be used to enhance development and disease resistance of crop species where growth-promoting and protective microbes may have been lost. During seedling establishment, seedlings may be infected by several fungal pathogens that are seed or soil [...] Read more.
Non-cultivated plants carry microbial endophytes that may be used to enhance development and disease resistance of crop species where growth-promoting and protective microbes may have been lost. During seedling establishment, seedlings may be infected by several fungal pathogens that are seed or soil borne. Several species of Fusarium, Pythium and other water moulds cause seed rots during germination. Fusarium blights of seedlings are also very common and significantly affect seedling development. In the present study we screened nine endophytic bacteria isolated from the seeds of invasive Phragmites australis by inoculating onto rice, Bermuda grass (Cynodon dactylon), or annual bluegrass (Poa annua) seeds to evaluate plant growth promotion and protection from disease caused by Fusarium oxysporum. We found that three bacteria belonging to genus Pseudomonas spp. (SLB4-P. fluorescens, SLB6-Pseudomonas sp. and SY1-Pseudomonas sp.) promoted seedling development, including enhancement of root and shoot growth, and stimulation of root hair formation. These bacteria were also found to increase phosphate solubilization in in vitro experiments. Pseudomonas sp. (SY1) significantly protected grass seedlings from Fusarium infection. In co-culture experiments, strain SY1 strongly inhibited fungal pathogens with 85.71% growth inhibition of F. oxysporum, 86.33% growth inhibition of Curvularia sp. and 82.14% growth inhibition of Alternaria sp. Seedlings previously treated with bacteria were found much less infected by F. oxysporum in comparison to non-treated controls. On microscopic observation we found that bacteria appeared to degrade fungal mycelia actively. Metabolite products of strain SY1 in agar were also found to inhibit fungal growth on nutrient media. Pseudomonas sp. (SY1) was found to produce antifungal volatiles. Polymerase chain reaction (PCR) amplification using specific primers for pyrrolnitirin synthesis and HCN (hydrogen cyanide) production suggested presence of genes for both compounds in the genome of SY1. HCN was detected in cultures of SY1. We conclude that microbes from non-cultivated plants may provide disease protection and promote growth of crop plants. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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Open AccessArticle Bacterial Microbiota of Rice Roots: 16S-Based Taxonomic Profiling of Endophytic and Rhizospheric Diversity, Endophytes Isolation and Simplified Endophytic Community
Microorganisms 2018, 6(1), 14; https://doi.org/10.3390/microorganisms6010014
Received: 20 November 2017 / Revised: 23 January 2018 / Accepted: 8 February 2018 / Published: 11 February 2018
Cited by 5 | PDF Full-text (2368 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Rice is currently the most important food crop in the world and we are only just beginning to study the bacterial associated microbiome. It is of importance to perform screenings of the core rice microbiota and also to develop new plant-microbe models and [...] Read more.
Rice is currently the most important food crop in the world and we are only just beginning to study the bacterial associated microbiome. It is of importance to perform screenings of the core rice microbiota and also to develop new plant-microbe models and simplified communities for increasing our understanding about the formation and function of its microbiome. In order to begin to address this aspect, we have performed a 16S rDNA taxonomic bacterial profiling of the rhizosphere and endorhizosphere of two high-yield rice cultivars—Pionero 2010 FL and DANAC SD20A—extensively grown in Venezuela in 2014. Fifteen putative bacterial endophytes were then isolated from surface-sterilized roots and further studied in vitro and in planta. We have then performed inoculation of rice seedlings with a simplified community composed by 10 of the isolates and we have tracked them in the course of 30 days in greenhouse cultivation. The results obtained suggest that a set was able to significantly colonize together the rice endorhizospheres, indicating possible cooperation and the ability to form a stable multispecies community. This approach can be useful in the development of microbial solutions for a more sustainable rice production. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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Open AccessArticle Inoculation with Azospirillum sp. and Herbaspirillum sp. Bacteria Increases the Tolerance of Maize to Drought Stress
Microorganisms 2017, 5(3), 41; https://doi.org/10.3390/microorganisms5030041
Received: 28 April 2017 / Revised: 10 July 2017 / Accepted: 24 July 2017 / Published: 26 July 2017
Cited by 9 | PDF Full-text (2326 KB) | HTML Full-text | XML Full-text
Abstract
Stress drought is an important abiotic factor that leads to immense losses in crop yields around the world. Strategies are urgently needed to help plants adapt to drought in order to mitigate crop losses. Here we investigated the bioprotective effects of inoculating corn [...] Read more.
Stress drought is an important abiotic factor that leads to immense losses in crop yields around the world. Strategies are urgently needed to help plants adapt to drought in order to mitigate crop losses. Here we investigated the bioprotective effects of inoculating corn grown under drought conditions with two types of plant growth-promoting rhizobacteria (PGPR), A. brasilense, strain SP-7, and H. seropedicae, strain Z-152. Plants inoculated with the bacteria were grown in a greenhouse with perlite as a substrate. Two hydric conditions were tested: normal well-watered conditions and drought conditions. Compared to control non-inoculated plants, those that were inoculated with PGPR bacteria showed a higher tolerance to the negative effects of water stress in drought conditions, with higher biomass production; higher carbon, nitrogen, and chlorophyll levels; and lower levels of abscisic acid and ethylene, which are plant hormones that affect the stress response. The oxidative stress levels of these plants were similar to those of non-inoculated plants grown in well-watered conditions, showing fewer injuries to the cell membrane. We also noted higher relative water content in the vegetal tissue and better osmoregulation in drought conditions in inoculated plants, as reflected by significantly lower proline content. Finally, we observed lower gene expression of ZmVP14 in the inoculated plants; notably, ZmVP14 is involved in the biosynthesis of abscisic acid. Taken together, these results demonstrate that these bacteria could be used to help plants cope with the negative effects of drought stress conditions. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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Review

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Open AccessReview Bacterial Endophyte Colonization and Distribution within Plants
Microorganisms 2017, 5(4), 77; https://doi.org/10.3390/microorganisms5040077
Received: 3 November 2017 / Revised: 21 November 2017 / Accepted: 23 November 2017 / Published: 25 November 2017
Cited by 11 | PDF Full-text (1687 KB) | HTML Full-text | XML Full-text
Abstract
The plant endosphere contains a diverse group of microbial communities. There is general consensus that these microbial communities make significant contributions to plant health. Both recently adopted genomic approaches and classical microbiology techniques continue to develop the science of plant-microbe interactions. Endophytes are [...] Read more.
The plant endosphere contains a diverse group of microbial communities. There is general consensus that these microbial communities make significant contributions to plant health. Both recently adopted genomic approaches and classical microbiology techniques continue to develop the science of plant-microbe interactions. Endophytes are microbial symbionts residing within the plant for the majority of their life cycle without any detrimental impact to the host plant. The use of these natural symbionts offers an opportunity to maximize crop productivity while reducing the environmental impacts of agriculture. Endophytes promote plant growth through nitrogen fixation, phytohormone production, nutrient acquisition, and by conferring tolerance to abiotic and biotic stresses. Colonization by endophytes is crucial for providing these benefits to the host plant. Endophytic colonization refers to the entry, growth and multiplication of endophyte populations within the host plant. Lately, plant microbiome research has gained considerable attention but the mechanism allowing plants to recruit endophytes is largely unknown. This review summarizes currently available knowledge about endophytic colonization by bacteria in various plant species, and specifically discusses the colonization of maize plants by Populus endophytes. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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Open AccessReview Combating Fusarium Infection Using Bacillus-Based Antimicrobials
Microorganisms 2017, 5(4), 75; https://doi.org/10.3390/microorganisms5040075
Received: 14 October 2017 / Revised: 14 November 2017 / Accepted: 16 November 2017 / Published: 22 November 2017
Cited by 6 | PDF Full-text (3188 KB) | HTML Full-text | XML Full-text
Abstract
Despite efforts to control toxigenic Fusarium species, wilt and head-blight infections are destructive and economically damaging diseases that have global effects. The utilization of biological control agents in disease management programs has provided an effective, safe, and sustainable means to control Fusarium-induced [...] Read more.
Despite efforts to control toxigenic Fusarium species, wilt and head-blight infections are destructive and economically damaging diseases that have global effects. The utilization of biological control agents in disease management programs has provided an effective, safe, and sustainable means to control Fusarium-induced plant diseases. Among the most widely used microbes for biocontrol agents are members of the genus Bacillus. These species influence plant and fungal pathogen interactions by a number of mechanisms such as competing for essential nutrients, antagonizing pathogens by producing fungitoxic metabolites, or inducing systemic resistance in plants. The multivariate interactions among plant-biocontrol agent-pathogen are the subject of this study, in which we survey the advances made regarding the research on the Bacillus-Fusarium interaction and focus on the principles and mechanisms of action among plant-growth promoting Bacillus species. In particular, we highlight their use in limiting and controlling Fusarium spread and infestations of economically important crops. This knowledge will be useful to define strategies for exploiting this group of beneficial bacteria for use as inoculants by themselves or in combination with other microbes for enhanced crop protection. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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Open AccessReview Transmission of Bacterial Endophytes
Microorganisms 2017, 5(4), 70; https://doi.org/10.3390/microorganisms5040070
Received: 20 October 2017 / Revised: 6 November 2017 / Accepted: 7 November 2017 / Published: 10 November 2017
Cited by 15 | PDF Full-text (1650 KB) | HTML Full-text | XML Full-text
Abstract
Plants are hosts to complex communities of endophytic bacteria that colonize the interior of both below- and aboveground tissues. Bacteria living inside plant tissues as endophytes can be horizontally acquired from the environment with each new generation, or vertically transmitted from generation to [...] Read more.
Plants are hosts to complex communities of endophytic bacteria that colonize the interior of both below- and aboveground tissues. Bacteria living inside plant tissues as endophytes can be horizontally acquired from the environment with each new generation, or vertically transmitted from generation to generation via seed. A better understanding of bacterial endophyte transmission routes and modes will benefit studies of plant–endophyte interactions in both agricultural and natural ecosystems. In this review, we provide an overview of the transmission routes that bacteria can take to colonize plants, including vertically via seeds and pollen, and horizontally via soil, atmosphere, and insects. We discuss both well-documented and understudied transmission routes, and identify gaps in our knowledge on how bacteria reach the inside of plants. Where little knowledge is available on endophytes, we draw from studies on bacterial plant pathogens to discuss potential transmission routes. Colonization of roots from soil is the best studied transmission route, and probably the most important, although more studies of transmission to aerial parts and stomatal colonization are needed, as are studies that conclusively confirm vertical transfer. While vertical transfer of bacterial endophytes likely occurs, obligate and strictly vertically transferred symbioses with bacteria are probably unusual in plants. Instead, plants appear to benefit from the ability to respond to a changing environment by acquiring its endophytic microbiome anew with each generation, and over the lifetime of individuals. Full article
(This article belongs to the Special Issue Symbiotic Plant-Bacterial Endospheric Interactions)
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