rhizosphere colonization
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2022 ◽  
Vol 8 (1) ◽  
Author(s):  
Esther Blanco-Romero ◽  
David Durán ◽  
Daniel Garrido-Sanz ◽  
Rafael Rivilla ◽  
Marta Martín ◽  
...  

Rhizosphere colonization by bacteria involves molecular and cellular mechanisms, such as motility and chemotaxis, biofilm formation, metabolic versatility, or biosynthesis of secondary metabolites, among others. Nonetheless, there is limited knowledge concerning the main regulatory factors that drive the rhizosphere colonization process. Here we show the importance of the AmrZ and FleQ transcription factors for adaption in the plant growth-promoting rhizobacterium (PGPR) and rhizosphere colonization model Pseudomonas ogarae F113. RNA-Seq analyses of P. ogarae F113 grown in liquid cultures either in exponential and stationary growth phase, and rhizosphere conditions, revealed that rhizosphere is a key driver of global changes in gene expression in this bacterium. Regarding the genetic background, this work has revealed that a mutation in fleQ causes considerably more alterations in the gene expression profile of this bacterium than a mutation in amrZ under rhizosphere conditions. The functional analysis has revealed that in P. ogarae F113, the transcription factors AmrZ and FleQ regulate genes involved in diverse bacterial functions. Notably, in the rhizosphere, these transcription factors antagonistically regulate genes related to motility, biofilm formation, nitrogen, sulfur, and amino acid metabolism, transport, signalling, and secretion, especially the type VI secretion systems. These results define the regulon of two important bifunctional transcriptional regulators in pseudomonads during the process of rhizosphere colonization.


2022 ◽  
Vol 12 ◽  
Author(s):  
Peng Shi ◽  
Jianli Zhang ◽  
Xingyue Li ◽  
Liyun Zhou ◽  
Hui Luo ◽  
...  

Efficient screening method is the prerequisite for getting plant growth-promoting (PGP) rhizobacteria (PGPR) which may play an important role in sustainable agriculture from the natural environment. Many current traditional preliminary screening criteria based on knowledge of PGP mechanisms do not always work well due to complex plant–microbe interactions and may lead to the low screening efficiency. More new screening criteria should be evaluated to establish a more effective screening system. However, the studies focused on this issue were not enough, and few new screening criteria had been proposed. The aim of this study was to analyze the correlation between the metabolic phenotypes of rhizobacterial isolates and their PGP ability. The feasibility of using these phenotypes as preliminary screening criteria for PGPR was also evaluated. Twenty-one rhizobacterial isolates were screened for their PGP ability, traditional PGP traits, and multiple metabolic phenotypes that are not directly related to PGP mechanisms, but are possibly related to rhizosphere colonization. Correlations between the PGP traits or metabolic phenotypes and increases in plant agronomic parameters were analyzed to find the indicators that are most closely related to PGP ability. The utilization of 11 nutrient substrates commonly found in root exudates, such as D-salicin, β-methyl-D-glucoside, and D-cellobiose, was significantly positively correlated with the PGP ability of the rhizobacterial isolates. The utilization of one amino acid and two organic acids, namely L-aspartic acid, α-keto-glutaric acid, and formic acid, was negatively correlated with PGP ability. There were no significant correlations between four PGP traits tested in this study and the PGP ability. The ability of rhizobacterial isolates to metabolize nutrient substrates that are identical or similar to root exudate components may act as better criteria than PGP traits for the primary screening of PGPR, because rhizosphere colonization is a prerequisite for PGPR to affect plants.


2021 ◽  
Author(s):  
Christina L Wiesmann ◽  
Yue Zhang ◽  
Morgan Alford ◽  
David Thoms ◽  
Melanie Dostert ◽  
...  

Members of the bacterial genus Pseudomonas form mutualistic, commensal and pathogenic associations with diverse hosts. The prevalence of host association across the genus suggests that symbiosis may be a conserved ancestral trait and that distinct symbiotic lifestyles may be more recently evolved. Here we show that the ColR/S two-component system, part of the Pseudomonas core genome, is functionally conserved between Pseudomonas aeruginosa and Pseudomonas fluorescens. Using plant rhizosphere colonization and virulence in a murine abscess model, we show that colR is required for commensalism with plants and virulence in animals. Comparative transcriptomics revealed that the ColR regulon has diverged between P. aeruginosa and P. fluorescens and deleting components of the ColR regulon revealed strain-specific, but not host specific, requirements for ColR-dependent genes. Collectively, our results suggest that ColR/S allows Pseudomonas to sense and respond to a host, but that the ColR-regulon has diverged between Pseudomonas strains with distinct lifestyles.


2021 ◽  
Author(s):  
Peng Shi ◽  
Jianli Zhang ◽  
Xingyue Li ◽  
Liyun Zhou ◽  
Hui Luo ◽  
...  

Abstract Aims Most preliminary screening criteria for plant growth-promoting (PGP) rhizobacteria (PGPR) are based on traditional knowledge of PGP mechanisms and do not always work well due to complex plant–microbe interactions. The aim of this study was to analyze the correlation between the metabolic phenotypes of rhizobacterial isolates and their PGP ability. The feasibility of using these phenotypes as preliminary screening criteria for PGPR was also evaluated. Methods Twenty-one rhizobacterial isolates were screened for their PGP ability, traditional PGP traits, and multiple metabolic phenotypes that are not directly related to PGP mechanisms, but are possibly related to rhizosphere colonization. Correlations between the PGP traits or metabolic phenotypes and increases in plant agronomic parameters were analyzed to find the indicators that are most closely related to PGP ability. Results The utilization of 11 nutrient substrates commonly found in root exudates, such as D-salicin, β-methyl-D-glucoside, D-cellobiose, D-maltose, D-trehalose, and dextrin, was significantly positively correlated with the PGP ability of the rhizobacterial isolates. The utilization of one amino acid and two organic acids, namely L-aspartic acid, α-keto-glutaric acid, and formic acid, was negatively correlated with PGP ability. There were no significant correlations between four PGP traits tested in this study and the PGP ability. Conclusion The ability of rhizobacterial isolates to metabolize nutrient substrates that are identical or similar to root exudate components may act as better criteria than PGP traits for the primary screening of PGPR, because rhizosphere colonization is a prerequisite for PGPR to affect plants.


2021 ◽  
Author(s):  
Tao Tian ◽  
Bingbing Sun ◽  
Haowen Shi ◽  
Tantan Gao ◽  
Yinghao He ◽  
...  

AbstractBeneficial rhizobacteria promote plant growth and protect plants against phytopathogens. Effective colonization on plant roots is critical for the rhizobacteria to exert beneficial activities. How bacteria migrate swiftly in the soil of semisolid or solid nature remains unclear. Here we report that sucrose, a disaccharide ubiquitously deployed by photosynthetic plants for fixed carbon transport and storage, and abundantly secreted from plant roots, promotes solid surface motility (SSM) and root colonization by Bacillus subtilis through a previously uncharacterized mechanism. Sucrose induces robust SSM by triggering a signaling cascade, first through extracellular synthesis of polymeric levan, which in turn stimulates strong production of surfactin and hyper-flagellation of the cells. B. subtilis poorly colonizes the roots of Arabidopsis thaliana mutants deficient in root-exudation of sucrose, while exogenously added sucrose selectively shapes the rhizomicrobiome associated with the tomato plant roots, promoting specifically bacilli and pseudomonad. We propose that sucrose activates a signaling cascade to trigger SSM and promote rhizosphere colonization by B. subtilis. Our findings also suggest a practicable approach to boost prevalence of beneficial Bacillus species in plant protection.


2020 ◽  
Author(s):  
Erqin Li ◽  
Henan Jiang ◽  
Corné M.J. Pieterse ◽  
Alexandre Jousset ◽  
Peter A.H.M. Bakker ◽  
...  

AbstractBeneficial plant root-associated microorganisms carry out a range of functions that are essential for plant performance. Establishment of a bacterium on plant roots, however, requires overcoming several challenges, including the ability to outcompete neighboring microorganisms and suppression of plant immunity. Forward and reverse genetics approaches have led to the identification of diverse mechanisms that are used by beneficial microorganisms to overcome these challenges such as the production of iron-chelating compounds, biofilm formation, or downregulation of plant immunity. However, how such mechanisms have developed from an evolutionary perspective is much less understood. In an attempt to study bacterial adaptation in the rhizosphere, we employed an experimental evolution approach to track the physiological and genetic dynamics of root-dwelling Pseudomonas protegens CHA0 in the Arabidopsis thaliana rhizosphere under axenic conditions. This simplified binary one plant, and one bacterium system allows for the amplification of key adaptive mechanisms for bacterial rhizosphere colonization. We found that mutations in global regulators, as well as in genes for siderophore production, cell surface decoration, attachment, and motility accumulated in parallel in our evolutionary experiment, underlining several different strategies of bacterial adaptation to the rhizosphere. In total we identified 35 mutations, including single-nucleotide polymorphisms, smaller indels and larger deletions, distributed over 28 genes in total. Altogether these results underscore the strength of experimental evolution to identify key genes and pathways for bacterial rhizosphere colonization, as well as highlighting a methodology for the development of elite beneficial microorganisms with enhanced root-colonizing capacities that can support sustainable agriculture in the future.


2020 ◽  
Vol 150 ◽  
pp. 104347 ◽  
Author(s):  
Federico Rivas-Franco ◽  
John G. Hampton ◽  
Josefina Narciso ◽  
Michael Rostás ◽  
Per Wessman ◽  
...  

2020 ◽  
Vol 3 (2) ◽  
pp. 187-197
Author(s):  
Mayara Silva Barbosa ◽  
Elisete Pains Rodrigues ◽  
Renata Stolf-Moreira ◽  
Cesar Augusto Tischer ◽  
André Luiz Martinez de Oliveira

2020 ◽  
Vol 8 (1) ◽  
pp. 71
Author(s):  
Xiyang Gao ◽  
Tao Li ◽  
Wenliang Liu ◽  
Yan Zhang ◽  
Di Shang ◽  
...  

1-aminocyclopropane-1-carboxylic acid (ACC) is a strong metabolism-dependent chemoattractant for the plant beneficial rhizobacterium Pseudomonas sp. UW4. It is unknown whether enhancing the metabolic rate of ACC can intensify the chemotaxis activity towards ACC and rhizocompetence. In this study, we selected four promoters to transcribe the UW4 ACC deaminase (AcdS) gene in the UW4 ΔAcdS mutant. PA is the UW4 AcdS gene promoter, PB20, PB10 and PB1 are synthetic promoters. The order of the AcdS gene expression level and AcdS activity of the four strains harboring the promoters were PB20 > PA > PB10 > PB1. Interestingly, the AcdS activity of the four strains and their parent strain UW4 was significantly positively correlated with their chemotactic activity towards ACC, rhizosphere colonization, roots elongation and dry weight promotion. The results released that enhancing the AcdS activity of PGPRenable them to achieve strong chemotactic responses to ACC, rhizocompetence and plant growth promotion.


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