Characterization of cellular, biochemical and genomic features of the diazotrophic plant growth-promoting bacterium Azospirillum sp. UENF-412522, a novel member of the Azospirillum genus

Given their remarkable beneficial effects on plant growth, several Azospirillum isolates currently integrate the formulations of various commercial inoculants. Our research group isolated a new strain, Azospirillum sp. UENF-412522, from passion fruit rhizoplane. This isolate uses carbon sources that are partially distinct from closely-related Azospirillum isolates. Scanning electron microscopy analysis and population counts demonstrate the ability of Azospirillum sp. UENF-412522 to colonize the surface of passion fruit roots. In vitro assays demonstrate the ability of Azospirillum sp. UENF-412522 to fix atmospheric nitrogen, to solubilize phosphate and to produce indole-acetic acid. Passion fruit plantlets inoculated with Azospirillum sp. UENF-41255 showed increased shoot and root fresh matter, as well as root dry matter, further highlighting its biotechnological potential for agriculture. We sequenced the genome of Azospirillum sp. UENF-412522 to investigate the genetic basis of its plant-growth promotion properties. We identified the key nif genes for nitrogen fixation, the complete PQQ operon for phosphate solubilization, the acdS gene that alleviates ethylene effects on plant growth, and the napCAB operon, which produces nitrite under anoxic conditions. We also found several genes conferring resistance to common soil antibiotics, which are critical for Azospirillum sp. UENF-412522 survival in the rhizosphere. Finally, we also assessed the Azospirillum pangenome and highlighted key genes involved in plant growth promotion. A phylogenetic reconstruction of the genus was also conducted. Our results support Azospirillum sp. UENF-412522 as a good candidate for bioinoculant formulations focused on plant growth promotion in sustainable systems.

Download Full-text

EFFICACY OF RHIZOBACTERIA ON PLANT GROWTH PROMOTION AND DISEASE SUPPRESSION IN VITRO

Acta Horticulturae ◽

10.17660/actahortic.2012.961.69 ◽

2012 ◽

pp. 525-532 ◽

Cited By ~ 1

Author(s):

S. Velivelli ◽

E. O'Herlihy ◽

B. Janczura ◽

B. Doyle Prestwich ◽

J. Ghyselinck ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Disease Suppression

Download Full-text

Exploitation of endophytic Pseudomonas sp. for plant growth promotion and colonization in rice

Journal of Applied and Natural Science ◽

10.31018/jans.v9i3.1359 ◽

2017 ◽

Vol 9 (3) ◽

pp. 1310-1316

Author(s):

Gurjot Kaur ◽

Poonam Sharma ◽

Deepika Chhabra ◽

Kailash Chand ◽

Gurjit Singh Mangat

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Acc Deaminase ◽

Pseudomonas Sp ◽

Bacterial Isolates ◽

Pgp Traits ◽

P Solubilization ◽

Fluorescent Pigment

The present investigation was carried out to exploit bacterial endophytes associated with root and leaf tissue of rice plant for plant growth promotion (PGP) and colonization study in vitro. Total 10 endophytic bacterial isolates (Pseudomonas sp.) were evaluate for PGP traits like P solubilization, production of Indole acetic acid (IAA), siderophore, ACC deaminase, protease, cellulase, fluorescent pigment, urease and denitrification activity. Out of 10 endophytic bacteria 30 %, 60 %, 20 %, 70 %, 10 % and 10 % were positive for siderophore, protease, cellulase, fluorescent pigment, urease and denitrification respectively. Maximum IAA production was recorded with isolate LRBLE7 (18.8 μgml-1) followed by LRBRE4 (16.0 μgml-1) and maximum P-solubilization was recorded with isolate LRBRE4 (5.8 mg 100 ml-1) followed by LRBLE7 (4.4 mg 100 ml-1). ACC deaminase production was recorded with isolate LRBLE6 (O.D=0.352 nm) followed by LRBRE5 (O.D=0.324nm). Three potential isolates (LRBRE4, LRBRE6 and LRBLE7) were selected on the basis of multiple PGP traits and were subjected to colonization study of rice seedling in vitro. Potential bacterial isolates can be exploited for improving growth and productivity in rice under sustainable management system.

Download Full-text

Potential for Plant Growth Promotion of Rhizobacteria Associated withSalicorniaGrowing in Tunisian Hypersaline Soils

BioMed Research International ◽

10.1155/2013/248078 ◽

2013 ◽

Vol 2013 ◽

pp. 1-13 ◽

Cited By ~ 84

Author(s):

Francesca Mapelli ◽

Ramona Marasco ◽

Eleonora Rolli ◽

Marta Barbato ◽

Hanene Cherif ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Crop Production ◽

Denaturing Gradient Gel Electrophoresis ◽

Growth Promotion ◽

Arid Ecosystems ◽

Acetic Acid Production ◽

Halotolerant Bacteria ◽

Microbiome Composition

Soil salinity and drought are among the environmental stresses that most severely affect plant growth and production around the world. In this study the rhizospheres ofSalicorniaplants and bulk soils were collected fromSebkhetandChotthypersaline ecosystems in Tunisia. Depiction of bacterial microbiome composition by Denaturing Gradient Gel Electrophoresis unveiled the occurrence of a high bacterial diversity associated withSalicorniaroot system. A large collection of 475 halophilic and halotolerant bacteria was established fromSalicorniarhizosphere and the surrounding bulk soil, and the bacteria were characterized for the resistance to temperature, osmotic and saline stresses, and plant growth promotion (PGP) features. TwentyHalomonasstrains showed resistance to a wide set of abiotic stresses and were able to perform different PGP activitiesin vitroat 5% NaCl, including ammonia and indole-3-acetic acid production, phosphate solubilisation, and potential nitrogen fixation. By using agfp-labelled strain it was possible to demonstrate thatHalomonasis capable of successfully colonisingSalicorniaroots in the laboratory conditions. Our results indicated that the culturable halophilic/halotolerant bacteria inhabiting salty and arid ecosystems have a potential to contribute to promoting plant growth under the harsh salinity and drought conditions. These halophilic/halotolerant strains could be exploited in biofertilizer formulates to sustain crop production in degraded and arid lands.

Download Full-text

Isolation, Biochemical and Genomic Characterization of Glyphosate Tolerant Bacteria to Perform Microbe-Assisted Phytoremediation

Frontiers in Microbiology ◽

10.3389/fmicb.2020.598507 ◽

2021 ◽

Vol 11 ◽

Author(s):

Francisco Massot ◽

Panagiotis Gkorezis ◽

Jonathan Van Hamme ◽

Damian Marino ◽

Bojana Spirovic Trifunovic ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Large Scale ◽

Agricultural Soils ◽

Growth Promotion ◽

Sole Source ◽

Bacterial Strains ◽

Positive Effects ◽

Assisted Phytoremediation

The large-scale use of the herbicide glyphosate leads to growing ecotoxicological and human health concerns. Microbe-assisted phytoremediation arises as a good option to remove, contain, or degrade glyphosate from soils and waterbodies, and thus avoid further spreading to non-target areas. To achieve this, availability of plant-colonizing, glyphosate-tolerant and -degrading strains is required and at the same time, it must be linked to plant-microorganism interaction studies focusing on a substantive ability to colonize the roots and degrade or transform the herbicide. In this work, we isolated bacteria from a chronically glyphosate-exposed site in Argentina, evaluated their glyphosate tolerance using the minimum inhibitory concentration assay, their in vitro degradation potential, their plant growth-promotion traits, and performed whole genome sequencing to gain insight into the application of a phytoremediation strategy to remediate glyphosate contaminated agronomic soils. Twenty-four soil and root-associated bacterial strains were isolated. Sixteen could grow using glyphosate as the sole source of phosphorous. As shown in MIC assay, some strains tolerated up to 10000 mg kg–1 of glyphosate. Most of them also demonstrated a diverse spectrum of in vitro plant growth-promotion traits, confirmed in their genome sequences. Two representative isolates were studied for their root colonization. An isolate of Ochrobactrum haematophilum exhibited different colonization patterns in the rhizoplane compared to an isolate of Rhizobium sp. Both strains were able to metabolize almost 50% of the original glyphosate concentration of 50 mg l–1 in 9 days. In a microcosms experiment with Lotus corniculatus L, O. haematophilum performed better than Rhizobium, with 97% of glyphosate transformed after 20 days. The results suggest that L. corniculatus in combination with to O. haematophilum can be adopted for phytoremediation of glyphosate on agricultural soils. An effective strategy is presented of linking the experimental data from the isolation of tolerant bacteria with performing plant-bacteria interaction tests to demonstrate positive effects on the removal of glyphosate from soils.

Download Full-text

An In vitro Study of Bio-Control and Plant Growth Promotion Potential of Salicaceae Endophytes

Frontiers in Microbiology ◽

10.3389/fmicb.2017.00386 ◽

2017 ◽

Vol 8 ◽

Cited By ~ 50

Author(s):

Shyam L. Kandel ◽

Andrea Firrincieli ◽

Pierre M. Joubert ◽

Patricia A. Okubara ◽

Natalie D. Leston ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

In Vitro Study ◽

Vitro Study

Download Full-text

Enhancement of verticillium wilt resistance in tomato transplants by in vitro co-culture of seedlings with a plant growth promoting rhizobacterium (Pseudomonas sp. strain PsJN)

Canadian Journal of Microbiology ◽

10.1139/w98-017 ◽

1998 ◽

Vol 44 (6) ◽

pp. 528-536 ◽

Cited By ~ 67

Author(s):

V K Sharma ◽

J Nowak

Keyword(s):

Plant Growth ◽

Verticillium Wilt ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Disease Suppression ◽

Pseudomonas Sp ◽

Plant Growth Promoting ◽

Growth Promoting

The potential utilization of a plant growth promoting rhizobacterium, Pseudomonas sp. strain PsJN, to enhance the resistance of tomato transplants to verticillium wilt was investigated. Plant growth and disease development were tested on the disease-susceptible cultivar Bonny Best after Verticillium dahliae infection of tissue culture plantlets bacterized in vitro (by co-culturing with the bacterium) and seedlings bacterized in vivo (after 3 weeks growth in the greenhouse). Significant differences in both disease suppression and plant growth were obtained between in vitro bacterized and nonbacterized (control) plants. The degree of protection afforded by in vitro bacterization depended on the inoculum density of V. dahliae; the best and worst protection occurred at the lowest (103 conidia ·mL-1) and highest (106 conidia ·mL-1) levels, respectively. In contrast, the in vivo bacterized tomatoes did not show plant growth promotion when compared to the nonbacterized control plants. When challenged with Verticillium, significant growth differences between in vivo bacterized plants (26.8% for shoot height) and nonbacterized controls were only seen at the 3rd week after inoculation. Compared with the in vitro inoculation, there was no delay in the verticillium wilt symptom expression, even at the lowest concentration of V. dahliae, by in vivo PsJN inoculation. These results suggest that endophytic colonization of tomato tissues is required for the Verticillium-resistance responses. Plant growth promotion preceeds the disease-resistance responses and may depend on the colonization thresholds and subsequent sensitization of hosts.Key words: Pseudomonas sp., plant growth promoting rhizobacterium, Verticillium dahliae, tomato, colonization, plant growth promotion, disease suppression.

Download Full-text

Inoculum density, temperature, and genotype effects on in vitro growth promotion and epiphytic and endophytic colonization of tomato (Lycopersicon esculentum L.) seedlings inoculated with a pseudomonad bacterium

Canadian Journal of Microbiology ◽

10.1139/m97-049 ◽

1997 ◽

Vol 43 (4) ◽

pp. 354-361 ◽

Cited By ~ 135

Author(s):

V. K. Pillay ◽

J. Nowak

Keyword(s):

Lycopersicon Esculentum ◽

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Bacterial Colonization ◽

Root Surface ◽

Inoculum Density ◽

Dual Culture ◽

Pseudomonas Sp

The effects of inoculum density (0, 4.6 × 107, 4.2 × 108, and 8.8 × 108 cfu∙mL−1), temperature (10, 20, and 30 °C), and plant genotype (cultivars Celebrity, Blazer, Scotia, and Mountain Delight) on bacterial colonization and plant growth promotion were investigated in a gnotobiotic system. An in vitro dual culture of tomato (Lycopersicon esculentum L.) plantlets and a Pseudomonas sp., strain PsJN, were used. Epiphytic (external) and endophytic (internal) bacterial populations were determined to evaluate plantlet colonization. Shoot and root biomass of bacterized plantlets was significantly higher (p ≤ 0.05) than that of nonbacterized controls. Growth promotion was best with inoculum densities of 3 × 108 – 7 × 108 cfu∙mL−1 at 20 °C, particularly in the early maturing cultivars Blazer and Scotia. Lower inoculum densities were required to maximize root growth (approximately 1 × 108 cfu∙mL−1) than shoot growth (approximately 3 × 108 cfu∙mL−1). Shoot surface populations did not vary with inoculum density or temperature, but the bacterium colonized the shoot exterior of cultivars Celebrity, Mountain Delight, and Scotia better than cultivar Blazer. The root surface populations increased linearly with increasing inoculum density (within a range of 107–108 cfu∙mL−1), decreased with increasing temperatures (from 10 to 30 °C), and were higher for the main season cultivar Celebrity than for cultivars Blazer, Scotia, and Mountain Delight. Populations of shoot endophytes did not vary with initial inoculum density or genotype but were affected by temperature; the highest colonization was at 10 °C. The number of root endophytes was also highest at 10 °C at the inoculum density of approximately 4 × 108 cfu∙mL−1 and did not vary with genotypes. The experiments clearly indicate that there was no relationship between root surface colonization and plant growth promotion. However, the range of inoculum levels (3 × 108 – 7 × 108 cfu∙mL−1) that promoted colonization of the inner root tissues (endophytic) also best promoted plant growth. A possible biostimulation threshold within the tissues of the inoculated plants under conditions favourable to the growth of tomato is proposed.Key words: Pseudomonas sp., tomato, colonization, growth promotion.

Download Full-text

Compost Inoculated with Fungi from a Mangrove Habitat Improved the Growth and Disease Defense of Vegetable Plants

Sustainability ◽

10.3390/su13010124 ◽

2020 ◽

Vol 13 (1) ◽

pp. 124

Author(s):

Fuad Ameen ◽

Ali A. Al-Homaidan

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

C:N Ratio ◽

Chemical Properties ◽

Plant Diseases ◽

Mangrove Forests ◽

Mangrove Fungi ◽

Disease Defense

Municipal organic wastes could be exploited as fertilizers, having been given the ability to suppress plant diseases by the inoculation of the waste with certain fungi in the composting process. Our aim was to develop a novel fertilizer using composting in combination with fungi associated with mangrove forests. Nine fungal species were isolated from a mangrove forest habitat and screened for their activity against five phytopathogenic fungi, their plant-growth promotion ability, and their phosphate solubilization ability. Two fungal isolates, Penicillium vinaceum and Eupenicillium hirayama, were inoculated into organic waste before the composting experiment. After 90 days, the physico-chemical properties of the compost (color, moisture, pH, C:N ratio and cation exchange capacity (CEC)) indicated the maturity of the compost. The C:N ratio decreased and the CEC value increased most in the compost with the inoculum of both mangrove fungi. The vegetable plants grown in the mangrove fungi-inoculated composts had a higher vigor index than those grown in the control compost. The seeds collected from the plants grown in the fungi-inoculated composts had higher disease defense ability than the seeds collected from the control compost. The results indicated that the properties of the fungi shown in vitro (antagonistic and plant-growth promotion) remained in the mature compost. The seeds of the plants acquired disease defense ability, which is a remarkable observation that is useful in sustainable agriculture.

Download Full-text

Profiling of Metabolites of Bacillus spp. and Their Application in Sustainable Plant Growth Promotion and Biocontrol

Frontiers in Sustainable Food Systems ◽

10.3389/fsufs.2021.605195 ◽

2021 ◽

Vol 5 ◽

Author(s):

Izzah Shahid ◽

Jun Han ◽

Sharoon Hanooq ◽

Kauser A. Malik ◽

Christoph H. Borchers ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Fungal Pathogens ◽

Extracellular Enzymes ◽

Nutrient Management ◽

Growth Promotion ◽

Antimicrobial Activities ◽

Ionization Mass ◽

Antifungal Metabolites

Bacillus spp. are well-characterized as efficient bioinoculants for sustainable plant growth promotion and biocontrol of phytopathogens. Members of this spp. exhibit the multifaceted beneficial traits that are involved in plant nutrition and antimicrobial activities against phytopathogens. Keeping in view their diverse potential, this study targeted the detailed characterization of three root-colonizing Bacillus strains namely B. amyloliquefaciens, B. subtilis, and B. tequilensis, characterized based on 16S rRNA sequencing homology. The strains exhibited better plant growth promotion and potent broad-spectrum antifungal activities and exerted 43–86% in-vitro inhibition of growth of eight fungal pathogens. All strains produced indole acetic acid (IAA) in the range of 0.067–0.147 μM and were positive for the production of extracellular enzymes such as cellulase, lipase, and protease. Ultra-performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (UPLC-ESI-MS/MS) analysis revealed the production of antifungal metabolites (AFMs) such as surfactins, iturins, fengycins, macrolactins, bacillomycin-D, and catechol-based siderophore bacillibactin which were further confirmed by amplifying the genes involved in the biosynthesis of these antimicrobial lipopeptides. When compared for the amounts of different cyclic-peptides produced by three Bacillus strains, B. amyloliquefaciens SB-1 showed the most noticeable amounts of all the antifungal compounds. Plant experiment results revealed that inoculation with phytohormone producing Bacillus spp. strains demonstrated substantial growth improvement of wheat biomass, number of spikes, and dry weight of shoots and roots. Results of this study indicate the biocontrol and biofertilizer potential of Bacillus spp. for sustainable plant nutrient management, growth promotion, and effective biocontrol of crop plants, particularly cultivated in the South Asian region.

Download Full-text

Genomic Analysis of the Endophytic Stenotrophomonas Strain 169 Reveals Features Related to Plant-Growth Promotion and Stress Tolerance

Frontiers in Microbiology ◽

10.3389/fmicb.2021.687463 ◽

2021 ◽

Vol 12 ◽

Author(s):

Kristina Ulrich ◽

Michael Kube ◽

Regina Becker ◽

Volker Schneck ◽

Andreas Ulrich

Keyword(s):

Plant Growth ◽

Stress Tolerance ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Whole Genome Sequence ◽

Plant Colonization ◽

Rrna Gene ◽

Promote Plant Growth ◽

Physiological Tests

Plant-associated Stenotrophomonas isolates have great potential for plant growth promotion, especially under stress conditions, due to their ability to promote tolerance to abiotic stresses such as salinity or drought. The endophytic strain Stenotrophomonas sp. 169, isolated from a field-grown poplar, increased the growth of inoculated in vitro plants, with a particular effect on root development, and was able to stimulate the rooting of poplar cuttings in the greenhouse. The strain produced high amounts of the plant growth-stimulating hormone auxin under in vitro conditions. The comparison of the 16S rRNA gene sequences and the phylogenetic analysis of the core genomes showed a close relationship to Stenotrophomonas chelatiphaga and a clear separation from Stenotrophomonas maltophilia. Whole genome sequence analysis revealed functional genes potentially associated with attachment and plant colonization, growth promotion, and stress protection. In detail, an extensive set of genes for twitching motility, chemotaxis, flagella biosynthesis, and the ability to form biofilms, which are connected with host plant colonization, could be identified in the genome of strain 169. The production of indole-3-acetic acid and the presence of genes for auxin biosynthesis pathways and the spermidine pathway could explain the ability to promote plant growth. Furthermore, the genome contained genes encoding for features related to the production of different osmoprotective molecules and enzymes mediating the regulation of stress tolerance and the ability of bacteria to quickly adapt to changing environments. Overall, the results of physiological tests and genome analysis demonstrated the capability of endophytic strain 169 to promote plant growth. In contrast to related species, strain 169 can be considered non-pathogenic and suitable for biotechnology applications.

Download Full-text