-
Frontiers in Plant Science 2020Used mainly for sucrose production, sugar beet is one of the most important crops in Castilla y León (Spain). Several studies have demonstrated the benefits of...
Used mainly for sucrose production, sugar beet is one of the most important crops in Castilla y León (Spain). Several studies have demonstrated the benefits of microorganisms in different crop management programs, among which Plant Growth Promoting Rhizobacteria (PGPR). This research aims to assess the beneficial effects of two PGPRs strains ( Pf0-1 and CECT 462) on sugar beet () production. Three treatments: a PGPRs co-inoculation assay of untreated seeds without any chemical treatment (TB), a conventional treatment with commercial seeds and fungicide application (TT); and a control with seeds without protective coating, bacterial inoculation and chemical treatment (ST). The efficacy of PGPRs inoculation on sugar beet production was determined measuring periodically the photosynthetic status of plants, and the final yield and quality of tubers. Aerial and root plant biomass, maximum beet perimeter, polarization, and sugar values of the sugar beet plants inoculated with PGPRs showed higher values and significant differences to sugar beet subjected to other treatments. We could see that PGPRs inoculation (TB treatment) produced significant differences in the quantum yield of PSII (ΦPSII). TB showed the highest value for ΦPSII and the NPQ (non-photochemical quenching), the lowest value, even though the PSII (maximum quantum yield of photosystem II) was very similar in all treatments. The two assayed PGPR strains triggered a significant increase in sugar beet production yield and quality. PGPRs inoculation techniques could be used in different crops and they could be applied as biofertilizers, improving the agricultural production.
PubMed: 33414799
DOI: 10.3389/fpls.2020.604898 -
Frontiers in Plant Science 2020Application of plant growth promoting bacteria may induce plant salt stress tolerance, however the underpinning microbial and plant mechanisms remain poorly understood....
Application of plant growth promoting bacteria may induce plant salt stress tolerance, however the underpinning microbial and plant mechanisms remain poorly understood. In the present study, the specific role of phenazine production by rhizosphere-colonizing in mediating the inhibitory effects of salinity on wheat seed germination and seedling growth in four different varieties was investigated using 30-84 (wild type) and isogenic derivatives deficient or enhanced in phenazine production. The results showed that varieties differed in how they responded to the salt stress treatment and the benefits derived from colonization by 30-84. In all varieties, the salt stress treatment significantly reduced seed germination, and in seedlings, reduced relative water content, increased reactive oxygen species (ROS) levels in leaves, and in three of four varieties, reduced shoot and root production compared to the no salt stress treatment. Inoculation of seeds with 30-84 wild type or derivatives promoted salt-stress tolerance in seedlings of the four commercial winter wheat varieties tested, but the salt-stress tolerance phenotype was not entirely due to phenazine production. For example, all derivatives (including the phenazine-producing mutant) significantly improved relative water content in two varieties, Iba and CV 1, for which the salt stress treatment had a large impact. Importantly, all derivatives enabled the salt inhibited wheat varieties studied to maintain above ground productivity in saline conditions. However, only phenazine-producing derivatives enhanced the shoot or root growth of seedlings of all varieties under nonsaline conditions. Notably, ROS accumulation was reduced, and antioxidant enzyme (catalase) activity enhanced in the leaves of seedlings grown in saline conditions that were seed-treated with phenazine-producing derivatives as compared to noninoculated seedlings. The results demonstrate the capacity of to improve salt tolerance in wheat seedlings by promoting plant growth and reducing osmotic stress and a role for bacterial phenazine production in reducing redox stress.
PubMed: 33133116
DOI: 10.3389/fpls.2020.575314 -
Molecular Microbiology Aug 2021Pseudomonas chlororaphis HT66 exhibits strong antagonistic activity against various phytopathogenic fungi due to its main antibiotic phenazine-1-carboxamide (PCN). PCN...
Lon protease downregulates phenazine-1-carboxamide biosynthesis by degrading the quorum sensing signal synthase PhzI and exhibits negative feedback regulation of Lon itself in Pseudomonas chlororaphis HT66.
Pseudomonas chlororaphis HT66 exhibits strong antagonistic activity against various phytopathogenic fungi due to its main antibiotic phenazine-1-carboxamide (PCN). PCN gene cluster consists of phzABCDEFG, phzH, phzI, and phzR operons. phzABCDEFG transcription is activated by the PhzI/R quorum sensing system. Deletion of the lon gene encoding an ATP-dependent protease resulted in significant enhancement of PCN production in strain HT66. However, the regulatory pathway and mechanism of Lon on PCN biosynthesis remain unknown. Here, lon mutation was shown to significantly improve antimicrobial activity of strain HT66. The N-acyl-homoserine lactone synthase PhzI mediates the negative regulation of PCN biosynthesis and phzABCDEFG transcription by Lon. Western blot showed that PhzI protein abundance and stability were significantly enhanced by lon deletion. The in vitro degradation assay suggested that Lon could directly degrade PhzI protein. However, Lon with an amino acid replacement (S -A) could not degrade PhzI protein. Lon-recognized region was located within the first 50 amino acids of PhzI. In addition, Lon formed a new autoregulatory feedback circuit to modulate its own degradation by other potential proteases. In summary, we elucidated the Lon-regulated pathway mediated by PhzI during PCN biosynthesis and the molecular mechanism underlying the degradation of PhzI by Lon in P. chlororaphis HT66.
Topics: Antifungal Agents; Bacterial Proteins; Down-Regulation; Feedback, Physiological; Gene Deletion; Gene Expression Regulation, Bacterial; Phenazines; Protease La; Pseudomonas chlororaphis; Quorum Sensing
PubMed: 34097792
DOI: 10.1111/mmi.14764 -
Microbiological Research Jan 2024Pseudomonas chlororaphis PCL1606 (PcPCL1606) is a model rhizobacterium used to study beneficial bacterial interactions with the plant rhizosphere. Many of its beneficial...
Pseudomonas chlororaphis PCL1606 (PcPCL1606) is a model rhizobacterium used to study beneficial bacterial interactions with the plant rhizosphere. Many of its beneficial phenotypes depend on the production of the antifungal compound 2-hexyl, 5-propyl resorcinol (HPR). Transcriptomic analysis of PcPCL1606 and the deletional mutant in HPR production ΔdarB strain, assigned an additional regulatory role to HPR, and allowed the detection of differentially expressed genes during the bacterial interaction with the avocado rhizosphere. Interestingly, the putative genes phaG (PCL1606_46820) and phaI (PCL1606_56560), with a predicted role in polyhydroxyalkanoate biosynthesis, were detected to be under HPR control. Both putative genes were expressed in the HPR-producing wild-type strain, but strongly repressed in the derivative mutant ΔdarB, impaired in HPR production. Thus, a derivative mutant impaired in the phaG gene was constructed, characterized and compared with the wild-type strain PcPCL1606 and with the derivative mutant ΔdarB. The phaG mutant had strongly reduced PHA production by PcPCL1606, and displayed altered phenotypes involved in bacterial survival on the plant roots, such as tolerance to high temperature and hydrogen peroxide, and decreased root survival, in a similar way that the ΔdarB mutant. On the other hand, the phaG mutant does not have altered resistance to desiccation, motility, biofilm formation or adhesion phenotypes, as displayed by the HPR-defective ΔdarB mutant have. Interestingly, the mutant defective in PHA production also lacked a biocontrol phenotype against the soilborne pathogenic fungus Rosellinia necatrix, even when the derivative mutant still produced the antifungal HPR compound, demonstrating that the final biocontrol phenotype of PcPCL1606 first requires bacterial survival and adaptation traits to the soil and rhizosphere environment.
Topics: Pseudomonas chlororaphis; Antifungal Agents; Plant Roots; Bacterial Proteins
PubMed: 37863020
DOI: 10.1016/j.micres.2023.127527 -
Frontiers in Plant Science 2023The management of soybean rust (SBR) caused by the obligate fungus mostly relies on the use of synthetic fungicides, especially in areas where the disease inflicts...
The management of soybean rust (SBR) caused by the obligate fungus mostly relies on the use of synthetic fungicides, especially in areas where the disease inflicts serious yield losses. The reliance on synthetic fungicides to manage this disease has resulted in resistance of populations to most fungicides. In this study, bacteria isolated from diverse environments were evaluated for their biocontrol potential against using soybean detached-leaf method and on-plant in the growth chamber, greenhouse, and field. Among 998 bacterial isolates evaluated using the detached-leaf method; 58% were isolated from plant-related materials, 27% from soil, 10% from insects, and 5% from other environments. Of the isolates screened, 73 were active (they had ⪖ 75% rust reduction) with an active rate of 7.3%. From the active isolates, 65 isolates were re-tested on-plant in the growth chamber for activity confirmation. In the confirmation test, 49 bacteria isolated from plant-related materials maintained their activity with a confirmation rate of 75%. The majority of bacteria with confirmed activity belonged to the taxonomic classes Bacilli and Gammaproteobacteria (70%). Active isolates were prioritized for greenhouse and field testing based on activity in the initial screen and confirmation test. Six bacterial isolates AFS000009 (), AFS032321 (), AFS042929 (), AFS065981 (), AFS090698 (), and AFS097295 () were selected from those bacteria that maintained activity in the confirmation test and were evaluated in the greenhouse, and five among them were evaluated in the field. From the Alabama field evaluation, all bacterial isolates reduced rust infection as well as azoxystrobin (Quadris at 0.3 L/ha) used as the fungicide control ( > 0.05). Moreover, the scanning electron micrographs demonstrated evidence of antagonistic activity of AFS000009 and AFS032321 against urediniospores. Bacterial isolates that consistently showed activity comparable to that of azoxystrobin can be improved through fermentation and formulation optimization, developed, and deployed. These bacteria strains would provide a valuable alternative to the synthetic fungicides and could play a useful role in integrated disease management programs for this disease.
PubMed: 36818841
DOI: 10.3389/fpls.2023.1080116 -
Polymers Dec 2021Alginate is a common agent used for microencapsulation; however, the formed capsule is easily damaged. Therefore, alginate requires blending with other biopolymers to...
Alginate is a common agent used for microencapsulation; however, the formed capsule is easily damaged. Therefore, alginate requires blending with other biopolymers to reduce capsule vulnerability. Whey protein is one polymer that can be incorporated with alginate to improve microcapsule structure. In this study, three different encapsulation methods (extrusion, emulsification, and spray drying) were tested for their ability to stabilize microencapsulated strain VUPF506. Extrusion and emulsification methods enhanced encapsulation efficiency by up to 80% and gave the best release patterns over two months. A greenhouse experiment using potato plants treated with alginate-whey protein microcapsules showed a decrease in disease intensity of up to 70%. This is because whey protein is rich in amino acids and can serve as a resistance induction agent for the plant. In this study, the use of CNT in the ALG-WP system increased the rooting and proliferation and reduced physiological complication. The results of this study showed that the technique used in encapsulation could have a significant effect on the efficiency and persistence of probiotic bacteria. Whole genome sequence analysis of strain VUPF506 identified it as and revealed some genes that control pathogens.
PubMed: 34883770
DOI: 10.3390/polym13234269 -
Molecules (Basel, Switzerland) Nov 2023Polycyclic aromatic hydrocarbons (PAHs) are common xenobiotics that are detrimental to the environment and human health. Bacterial endophytes, having the capacity to...
Polycyclic aromatic hydrocarbons (PAHs) are common xenobiotics that are detrimental to the environment and human health. Bacterial endophytes, having the capacity to degrade PAHs, and plant growth promotion (PGP) may facilitate their biodegradation. In this study, phenanthrene (PHE) utilization of a newly isolated PGP endophytic strain of 23aP and factors affecting the process were evaluated. The data obtained showed that strain 23aP utilized PHE in a wide range of concentrations (6-100 ppm). Ethyl-acetate-extractable metabolites obtained from the PHE-enriched cultures were analyzed by gas chromatography-mass spectrometry (GC-MS) and thin-layer chromatography (HPTLC). The analysis identified phthalic acid, 3-(1-naphthyl)allyl alcohol, 2-hydroxybenzalpyruvic acid, -naphthol, and 2-phenylbenzaldehyde, and allowed us to propose that the PHE degradation pathway of strain 23aP is initiated at the 1,2-, 3,4-carbon positions, while the 9,10-C pathway starts with non-enzymatic oxidation and is continued by the downstream phthalic pathway. Moreover, the production of the biosurfactants, mono- (Rha-C-C, Rha-C-C, Rha-C-C, and Rha-C-C) and dirhamnolipids (Rha-Rha-C-C), was confirmed using direct injection-electrospray ionization-mass spectrometry (DI-ESI-MS) technique. Changes in the bacterial surface cell properties in the presence of PHE of increased hydrophobicity were assessed with the microbial adhesion to hydrocarbons (MATH) assay. Altogether, this suggests the strain 23aP might be used in bioaugmentation-a biological method supporting the removal of pollutants from contaminated environments.
Topics: Humans; Pseudomonas chlororaphis; Phenanthrenes; Polycyclic Aromatic Hydrocarbons; Spectrometry, Mass, Electrospray Ionization; Bacteria; Biodegradation, Environmental
PubMed: 38005303
DOI: 10.3390/molecules28227581 -
Frontiers in Microbiology 2019The specific role of phenazines produced by rhizosphere-colonizing in mediating wheat seedling drought-stress tolerance and recovery from water deficit was investigated...
The specific role of phenazines produced by rhizosphere-colonizing in mediating wheat seedling drought-stress tolerance and recovery from water deficit was investigated using 30-84 and isogenic derivatives deficient or enhanced in phenazine production compared to wild type. Following a 7-day water deficit, seedlings that received no-inoculum or were colonized by the phenazine mutant wilted to collapse, whereas seedlings colonized by phenazine producers displayed less severe symptoms. After a 7-day recovery period, survival of seedlings colonized by phenazine-producing strains exceeded 80%, but was less than 60% for no-inoculum controls. A second 7-day water deficit reduced overall survival rates to less than 10% for no-inoculum control seedlings, whereas survival was ∼50% for seedlings colonized by phenazine-producers. The relative water content of seedlings colonized by phenazine-producers was 10-20% greater than for the no-inoculum controls at every stage of water deficit and recovery, resulting in higher recovery indices than observed for the no-inoculum controls. For 10-day water deficits causing the collapse of all seedlings, survival rates remained high for plants colonized by phenazine-producers, especially the enhanced phenazine producer (∼74%), relative to the no-inoculum control (∼25%). These observations indicate that seedlings colonized by the phenazine-producing strains suffered less from dehydration during water deficit and recovered better, potentially contributing to better resilience from a second drought/recovery cycle. Seedlings colonized by phenazine-producing strains invested more in root systems and produced 1.5 to 2 fold more root tips than seedlings colonized by the phenazine mutant or the no-inoculum controls when grown with or without water deficit. The results suggest that the presence of phenazine-producing bacteria in the rhizosphere provides wheat seedlings with a longer adjustment period resulting in greater drought-stress avoidance and resilience.
PubMed: 31354678
DOI: 10.3389/fmicb.2019.01590 -
Microorganisms Jul 2023Causing major health and ecological disturbances, polychlorinated biphenyls (PCBs) are persistent organic pollutants still recovered all over the world. Microbial PCB...
Causing major health and ecological disturbances, polychlorinated biphenyls (PCBs) are persistent organic pollutants still recovered all over the world. Microbial PCB biotransformation is a promising technique for depollution, but the involved molecular mechanisms remain misunderstood. Ligninolytic enzymes are suspected to be involved in many PCB transformations, but their assessments remain scarce. To further inventory the capabilities of microbes to transform PCBs through their ligninolytic enzymes, we investigated the role of oxidase and peroxidase among a set of microorganisms isolated from a historically PCB-contaminated site. Among 29 isolated fungi and 17 bacteria, this work reports for the first time the PCB-transforming capabilities from fungi affiliated to , , , , , , and genera and bacteria affiliated to , , , , , sp., , and . In the same way, this is the first report of fungal isolates affiliated to the specie and genus that displayed oxidase (putatively laccase) and peroxidase activity, respectively, enhanced in the presence of PCBs (more than 4-fold and 20-fold, respectively, compared to controls). Based on these results, the observed activities are suspected to be involved in PCB transformation.
PubMed: 37630447
DOI: 10.3390/microorganisms11081887 -
Biotechnologia 2023Zinc is a vital micronutrient for all life forms, and Zn-solubilizing bacteria (ZSB) present in the soil convert inorganic zinc into forms available for plants. This...
Zinc is a vital micronutrient for all life forms, and Zn-solubilizing bacteria (ZSB) present in the soil convert inorganic zinc into forms available for plants. This study assessed ZSB isolated from cow dung for their plant growth-promoting (PGP) characteristics and potential to enhance tomato plant growth. The experiment assayed a total of 30 bacteria from cow dung for Zn-solubilization using insoluble ZnO and ZnCO. Atomic absorption spectroscopy quantitatively evaluated Zn-solubilization, and the isolates were further studied for Zn-solubilization and plant growth in . The CDS7 and CDS27 isolates were the most significant Zn-solubilizing strains. CDS7 exhibited increased ZnO solubility (32.1 mg/l) compared to CDS21 (23.7 mg/l). PGP trait quantitative results revealed that the CDS7 and CDS21 bacterial strains solubilized insoluble phosphate (287.2 and 217.7 μg/ml, respectively) and produced indole acetic acid (22.1 and 14.8 μg/ml, respectively). Based on 16S rRNA gene sequencing, CDS7 and CDS21 were identified as and , and 16S rDNA sequences were submitted to the GenBank database. Furthermore, ZSB strains were administered to tomato seeds under a pot study. The treatments with CDS7 inoculant and a consortium of both isolates were reported with maximum plant development (stem length 63.16 and 59.89 cm, respectively) and zinc content (3.13 and 2.36 mg/100 g, respectively) in tomato fruit compared to the control. In conclusion, microorganisms isolated from cow dung with PGP activity can improve Zn bioavailability and plant growth sustainably. They can be used as biofertilizers in agricultural fields to improve plant growth and production.
PubMed: 37427026
DOI: 10.5114/bta.2023.127205