Assessment of antagonistic and plant growth promoting activities of tomato endophytic bacteria in challenging with Verticillium dahliae under in-vitro and in- vivo conditions

Introduction: In recent years, there has been a considerable interest in the use of biological approaches, as an alternative to chemical fertilizers and pesticides to management of plant pathogens and improvement of crop productivity. Recently, endophytic bacteria have gained attention due to their efficient bio-control and plant growth promoting potentials. The objective of this study was to evaluate bio control and plant growth promoting ability of endophytic bacteria in challenging with Verticillium dahliae under in-vitro and greenhouse conditions. Materials and methods: Endophytic bacteria were isolated from tomato plants and their bio-control activity was screened based on dual culture method. Antifungal and their plant growth promoting traits such as production of volatile compounds, antibiotics, proteases, chitinases, hydrogen cyanide, siderophore, indole acetic acid and phosphate solubilizing were evaluated. Their effects on seed germination and growth parameters of seedlings under in-vitro condition and on the control of disease and tomato growth were evaluated in greenhouse. Results: In dual culture tests, FS67, FS167, FS300 and FS339 isolates showed significant antifungal activity and they were identified as Pseudomonas mosselli, P. fuorescence, Stenotrophomonas maltophilia and Acinetobacter calcoaceticus, respectively. All strains produced several kinds of antifungal and growth promoting agents under in-vitro conditions. They increased seed germination and growth parameters of seedlings. They also reduced the disease and improved the growth parameters of the plants in challenging with V. dahliae in greenhouse. Discussion and conclusion: The present study has shown that these endophytic bacteria have the bio-control and bio-fertilizer potentials, which make them suitable candidates as an alternative tool of chemicals in management of V. dahliae. Results indicated they might enhance tomato plant growth and health via various mechanisms and most of them probably employ more than one of these mechanisms

Detection of Beta-lactamase gene in the culturable bacteria isolated from agricultural, pasture and mining soils around mines in Hamedan, Iran

Introduction: Growing evidence exists that agriculture affects antibiotic resistance in human pathogens. Beta-lactam antibiotics are the most commonly used antimicrobial agents in many countries. The abundance of beta-lactamase encoding genes can be used as an indicator of antibiotic resistance in the environment. So, to determine the beta-lactamase resistance genes, the abundance of culturable bacteria having bla-TEM genesin the soils under different land uses wasexamined. Materials and methods: 44 Gram-positive and 34 Gram-negative bacteria plated on nutrient agar were isolated from agricultural, pasture and mining soils and selected to study the presence of TEM-class gene using PCR amplification. Antibiotic sensitivity test of bla-TEM+isolateswas done adopting the Kirby-Bauer disk diffusion method and antibiotic discs used were: ampicillin, amoxicillin, vancomicin, streptomycin, tetracycline and gentamicin. Finally, five multi-drug resistant and bla-TEM+ isolates were identified using universal primers. Results: The highest level of beta-lactamase genes was observed in the Gram-positive and Gram-negative isolates from the pasture soils. In the agricultural and mining soils, a high abundance of bla-TEM+ isolateswasfound which also showed resistance to beta-lactam antibiotics. The identified multi-drug resistant and bla-TEM+ isolates were from these genera: Achromobacter, Bacillus, Brevibacillus, Aminobacter and Brevundimonas. Discussion and conclusion: The high number of bla-TEM+ bacteria in all the soils may be attributed to the other important feature of bla genes which is their capability to extrude toxic compounds like heavy metals in contaminated environments. Sensitivity of some bla-TEM+ bacteria to beta-lactam antibiotics was interesting. This result shows that bla-TEM genes confer resistance to beta-lactamase inhibitors in a different degree. Some of the identified isolates were pathogen. These pathogens in soils can transfer to plants and human which induce health problems. A high abundance of bla-TEM+ bacteria in the agricultural soil indicates the inefficiency of beta-lactam antibiotics

Expression of Cre recombinase during transient phage infection permits efficient marker removal in Streptomyces

We report a system for the efficient removal of a marker flanked by two loxP sites in Streptomyces coelicolor, using a derivative of the temperate phage φC31 that expresses Cre recombinase during a transient infection. As the test case for this recombinant phage (called Cre-phage), we present the construction of an in-frame deletion of a gene, pglW, required for phage growth limitation or Pgl in S.coelicolor. Cre-phage was also used for marker deletion in other strains of S.coelicolor

Expression of Cre recombinase during transient phage infection permits efficient marker removal in Streptomyces

We report a system for the efficient removal of a marker flanked by two loxP sites in Streptomyces coelicolor, using a derivative of the temperate phage φC31 that expresses Cre recombinase during a transient infection. As the test case for this recombinant phage (called Cre-phage), we present the construction of an in-frame deletion of a gene, pglW, required for phage growth limitation or Pgl in S.coelicolor. Cre-phage was also used for marker deletion in other strains of S.coelicolor

Rhizosphere Bacterial Composition of the Sugar Beet Using SDS-PAGE Methodology

ABSTRACT The rhizosphere zone has been defined as the volume of soil directly influenced by the presence of living plant roots or soil compartment influenced by the root. During the growing season of 2014, the rhizobacteria of 23 sugar beet plants sampled from 12 sites in the west and north west of Iran were inventoried. Using a cultivation-dependent approach, a total of 217 bacteria were isolated from the rhizosphere. The bacterial isolates were tentatively grouped and documented based on polyacrylamide gel electrophoresis of whole-cell proteins and were found to represent 43 different protein electrotypes. The majority of the fingerprint types were found only on a single occasion. Fifty-nine percent of the strains belonged to the five bacterial species and identified as Stenotrophomonas maltophilia, Pseudomonas fluorescens, Pseudomonas aeruginosa, Stenotrophomonas rhizophila and Serratia marcescens. Minor occurring fingerprint types were identified as Flavobacterium spp, Erwinia spp, Acetobacter spp, Agrobacterium spp, Enterobacter spp, Aeromonas spp and Bacillus spp

Endophytic Bacteria Suppress Bacterial Wilt of Tomato Caused by Ralstonia solanacearum and Activate Defense-related Metabolites

Introduction: Phytopathogenic microorganisms affect plant health and burden a major threat to food production and ecosystem stability. Increasing the use of chemical pesticides for plant diseases control causes several negative effects on human and environment health. Furthermore, increasing public awareness about the side effects of them led to a research to find alternatives for these products. One of the alternative methods is bio-control utilizing plant associated antagonistic microorganisms. Materials and methods: In this study, 80 endophytic bacteria were isolated from tomato tissues. Their antagonistic activity screened based on agar diffusion test, against tomato bacterial wilt disease (Ralstonia solanacearum). They were identified based on the morphological, biochemical properties and 16s rRNA sequence analyses. These strains were evaluated in greenhouse and tested for their ability to induce the production of defense-related enzymes in plants e.g. Peroxidase (PO), polyphenoloxidase (PPO) and phenolics based on spectrophotometer method. Results: Results showed FS67, FS167 and FS184 strains had maximum inhibition zone forming. They identified as Pseudomonas mossellii, P. fuorescence and P. brassicacearum respectively. FS67 and FS167 strains significantly reduced disease in greenhouse. There was a significant increase in the activity of PO, PPO and phenolics in tomato plants treated with FS67, FS167 and pathogen. Discussion and conclusion: The present study has shown that P. mosselli and P. fuorescence might have the potential to control R. solanacearum. However, the good results obtained in vitro cannot be gained the same as those in greenhouse or field conditions. So, further experiments are needed to determine the effectiveness of these isolates under field conditions.This work support the view that increased defense enzymes activities could be involved, at least in part, in the beneficial effects of endophytic bacteria on plants growth in interaction of pathogens. This is the first report of antagonistic activity of Pseudomonas mossellii from Iran

Diversity and phylogeny of the bacterial strains isolated from nodules of fenugreek (Trigonella foenum-graecum L.) in Iran

8 páginas, 3 figuras, 2 tablasThe diversity of fenugreek (Trigonella foenum-graecum L.) microsymbionts has been barely studied even though it is of great interest for being a spice and a medicinal plant. Here, we analyzed 59 bacterial strains isolated from fenugreek nodules originating from different geographic and climatic areas of Iran. Most of these strains exhibit phenotypic characteristics compatible with rhizobia and they nodulate fenugreek. Analysis of the recA and atpD genes shows that representative strains of ERIC-BOX-PCR groups cluster with the type strains of Ensifer meliloti and E. kummerowiae as well as with strains capable of nodulating different Trigonella species found in other countries. The closeness of E. meliloti and E. kummerowiae suggests there is a need to revise the taxonomic status of the latter species. The nodC gene analysis shows that most Trigonella-nodulating strains belong to the symbiovar meliloti except those nodulating Trigonella arcuata in China, which belong to the symbiovar rigiduloides. This analysis shows that the type strains of E. kummerowiae, E. meliloti, and E. medicae belonged to three well-defined groups within the symbiovar meliloti, with the Iranian strains belonging to the E. kummerowiae subgroup. The small group of strains unable to nodulate fenugreek isolated in this study belong to Enterobacter cloacae, reported for the first time as being a possible endophyte of fenugreek nodules.Excellence Unit of the ‘Instituto de Investigación en Agrobiotecnología’ (CIALE) (CLU-2018–04) from the Regional Government of Castilla and León (Spain).Peer reviewe

Characterization of Potential Plant Growth-Promoting Rhizobacteria Isolated from Sunflower (Helianthus annuus L.) in Iran

Purpose: This study aims to characterize plant growth-promoting rhizobacteria (PGPR) in sunflowers growing in different locations at North-West of Iran. Materials and methods: Sunflower plants were collected from different regions of West-Azerbaijan, and rhizospheric bacterial strains were isolated and screened for PGP traits. Identification and characterization of the PGPR were conducted based on 16s rDNA sequences and phenotypic analysis, the strains clustered for genetic diversity by rep-PCR method. Results: Among the 80 bacterial isolates, 20 showed PGP traits and were selected for other potentials. All the selected isolates produced indole-3-acetic acid at the rate of 9.2–33.7 mg/ml. In addition, 13, 15, 12, and 16 were positive for phosphate solubilization, siderephore, hydrogen cyanide, and ammonia production, respectively. The results from a subsequent pot experiment indicated that PGPRs distinctly increased sun flower shoot and root length, shoot and root fresh weight, as well as shoot and root dry weight. Based on 16s rDNA sequences and biochemical and physiological characteristics, 20 PGPRs were identified as Pseudomonas fluorescens (five isolates), Pseudomonas aeruginosa (four isolates), Pseudomonas geniculata (one isolate), Bacillus subtilis (four isolates), Bacillus pumilus (two isolates), Stenotrophomonas maltophilia (two isolates), and Brevibacterium frigoritolerans (two isolates). In rep-PCR, PGPR isolates were differentiated into seven clusters (A–G) at 65% similarity level. These results demonstrated the existence of a considerable species richness and genetic diversity among PGPRs isolated from different regions of North-West of Iran. Conclusions: To the best of our knowledge, this is the first report for the identification and characterization of B. frigoritolerans as PGPR in sunflower plants

Biological control of Fusarium graminearum on wheat by antagonistic bacteria

Bacillus subtilis strains 53 and 71, Pseudomonas fluorescens biov1 strain 32 and Streptomyces sp. Strain 3 were evaluated as potential biological agents for control of fusarium head blight (FHB) caused by Fusarium graminearum. Mycelial growth of the pathogen was reduced by cell free and volatile metabolites of bacterial antagonists by 37%-97%. Streptomyces sp. Strain 3 reduced disease severity of FHB 21 d after inoculation. The yield of wheat from plants treated with Streptomyces sp. strain 3 and F. graminearum was significantly greater than in controls inoculated with the pathogen alone. Treatments with Streptomyces sp. alone increased the yield of wheat compared to the uninoculated controls

Characterization and molecular diversity of Iranian rhizobia isolated from faba bean

The diversity and phylogeny of 30 rhizobia isolated from nodules of faba bean plants grown on 5 geographic regions located in the East Azerbaijan province of Iran were examined using rep-PCR fingerprinting, sequence analysis of 16S rRNA accompanied with nodC genes. Based on cluster analysis of rep-PCR fingerprints, faba bean rhizobia isolates were differentiated into five clusters (A to E) at 80% similarity level. The cophenetic correlation coefficient for the dendrogram obtained from the combined dataset of BOX and ERIC primers was 0.942. The percentage of polymorphic loci was 59.2% using the BOX-PCR primer and 67.3% using the ERIC-PCR primers. The data obtained by rep-PCR fingerprinting showed high apparent correlation between genetic diversity and geographical origin of the isolates. The phylogenetic analysis based on 16S rRNA and nodC sequences showed that representative isolates were closely related to R. leguminosarum bv. viciae and R. fabae. To the best of our knowledge, this is first report of isolation and characterization of R. fabae from Iran