Pantoea Sp Research Articles

Screening, identification and phosphate-solubilizing characteristics of phosphate-solubilizing bacteria strain D2 (Pantoea sp.)in rhizosphere of Pinus tabuliformis in iron tailings yard.

Two strains of phosphate-solubilizing bacteria were isolated from the rhizosphere of Pinus tabuliformis in iron tailings vegetation restoration areas in Malan Town, Qianan City, Hebei Pro-vince. The bacterial strain D2 with strong phosphate-solubilizing capacity was obtained via screening with plate and shake flask. Based on the morphology, physiology and biochemistry, and the sequence analysis of 16S rDNA, the D2 was identified as a member of Pantoea sp. A fermentation experiment was conducted to investigate the effect of carbon and nitrogen sources on the phosphate-solubilizing capacity of the strain D2; under different nitrogen sources, the organic acids in liquid culture, as well as their types and contents were determined by high performance liquid chromatography. The results showed that the strain D2 was capable of efficiently solubilizing tricalcium phosphate, and the highest value of available phosphorus was up to 392.13 mg·L-1 in liquid culture. The strain D2 displayed the strongest phosphate-solubilizing capability when glucose and ammonium sulfate were used as carbon and nitrogen sources in the culture media, respectively. Under varied nitrogen sources, the resulting organic acids and their types and contents were different. When the nitrogen source in culture media was ammonium sulfate, ammonium chloride, potassium nitrate, sodium nitrate or ammonium nitrate, all four organic acids, including oxalic acid, formic acid, acetic acid and citric acid, were produced. In addition, malic acid was uniquely produced when ammonium sulfate, ammonium chloride or ammonium nitrate was used as the nitrogen source. By Pearson's correlation analysis, a significant positive correlation between the acetic acid content and the available phosphorus content was found (r=0.886, P<0.05), suggesting that acetic acid produced by strain D2 played an important role in promoting inorganic phosphorus dissolution, which was most likely to be one of the important phosphate-solubilizing mechanisms of the strain.

Killing Two Birds with One Stone: Natural Rice Rhizospheric Microbes Reduce Arsenic Uptake and Blast Infections in Rice.

Our recent work has shown that a rice thizospheric natural isolate, a Pantoea sp (hereafter EA106) attenuates Arsenic (As) uptake in rice. In parallel, yet another natural rice rhizospheric isolate, a Pseudomonas chlororaphis (hereafter EA105), was shown to inhibit rice blast pathogen Magnaporthe oryzae. Considering the above, we envisaged to evaluate the importance of mixed stress regime in rice plants subjected to both As toxicity and blast infections. Plants subjected to As regime showed increased susceptibility to blast infections compared to As-untreated plants. Rice blast pathogen M. oryzae showed significant resistance against As toxicity compared to other non-host fungal pathogens. Interestingly, plants treated with EA106 showed reduced susceptibility against blast infections in plants pre-treated with As. This data also corresponded with lower As uptake in plants primed with EA106. In addition, we also evaluated the expression of defense related genes in host plants subjected to As treatment. The data showed that plants primed with EA106 upregulated defense-related genes with or without As treatment. The data shows the first evidence of how rice plants cope with mixed stress regimes. Our work highlights the importance of natural association of plant microbiome which determines the efficacy of benign microbes to promote the development of beneficial traits in plants.

Identification of bacterial contaminants in polyherbal medicines used for the treatment of tuberculosis in Amatole District of the Eastern Cape Province, South Africa, using rapid 16S rRNA technique.

BackgroundPolyherbal medicines are used for the treatment of many diseases in many African and Asian communities. With the increasing use of these remedies, several investigations have shown that they are associated with a broad variety of residues and contaminants. This study investigates the presence of bacteria in the polyherbal medicines used for the treatment of tuberculosis (TB) in the Eastern Cape Province of South Africa.MethodsBacterial DNA was extracted from the polyherbal medicines, and a fragment of the bacterial 16S rRNA gene was amplified by PCR with universal primers 27F and 518R. The amplicons were visualised on agarose gel electrophoresis, followed by end repair and adaptor ligation. They were further purified and quantified using Library Preparation kit NEBNext® UltraT DNA Library Prep Kit for Illumina, and the amplicons were run on illumina’s MiSeq platform.ResultsDifferent bacterial species were identified in all each of the polyherbal medicines. Generally, the most prominent and common bacteria recovered from all the samples were Bacillus sp., Enterobacter sp., Klebsiella sp., Rahnella sp., Paenibacillus sp., Clostridium sp. and Pantoea sp. Others are Pseudomonas sp., Raoultella ornithinolytica, Salmonella enterica and Eubacterium moniliforme.ConclusionsThis study, thus, revealed the presence of pathogenic and non-pathogenic bacteria in the polyherbal medicines used for the treatment of tuberculosis in the study area. The implications of the findings are discussed in relation to the health care of the patients of tuberculosis in the study area, having in mind that they are immunocompromised individuals.

A Carotenoid-Deficient Mutant in Pantoea sp. YR343, a Bacteria Isolated from the Rhizosphere of Populus deltoides, Is Defective in Root Colonization.

The complex interactions between plants and their microbiome can have a profound effect on the health and productivity of the plant host. A better understanding of the microbial mechanisms that promote plant health and stress tolerance will enable strategies for improving the productivity of economically important plants. Pantoea sp. YR343 is a motile, rod-shaped bacterium isolated from the roots of Populus deltoides that possesses the ability to solubilize phosphate and produce the phytohormone indole-3-acetic acid (IAA). Pantoea sp. YR343 readily colonizes plant roots and does not appear to be pathogenic when applied to the leaves or roots of selected plant hosts. To better understand the molecular mechanisms involved in plant association and rhizosphere survival by Pantoea sp. YR343, we constructed a mutant in which the crtB gene encoding phytoene synthase was deleted. Phytoene synthase is responsible for converting geranylgeranyl pyrophosphate to phytoene, an important precursor to the production of carotenoids. As predicted, the ΔcrtB mutant is defective in carotenoid production, and shows increased sensitivity to oxidative stress. Moreover, we find that the ΔcrtB mutant is impaired in biofilm formation and production of IAA. Finally we demonstrate that the ΔcrtB mutant shows reduced colonization of plant roots. Taken together, these data suggest that carotenoids are important for plant association and/or rhizosphere survival in Pantoea sp. YR343.

Effects of biocontrol agents on suppression of damping-off in Cucumis sativus L. caused by Rhizoctonia solani

Biocontrol agents (Pseudomonas aeruginosa HB-15 and Pantoea sp. HB-22, alone or in combination) were applied on cucumber (Cucumis sativus L.) plants to evaluate their effect on suppressing damping-off caused by the fungal pathogen Rhizoctonia solani. Plant biomass, percent root mortality, phosphorus uptake, and the levels of stress-indicators NH3-NH4+ and proline in the plants were measured following the treatments. Additionally, gene expression induced by the biocontrol agents was compared to the gene expression induced by jasmonic acid and salicylic acid treatments. The biocontrol treatments increased fresh weight and phosphorus uptake, and reduced root mortality of the cucumber plants inoculated with the pathogen. No differences in plant ecophysiological responses were detected among biocontrol agent treatments. Concentrations of NH3-NH4+ and proline in the leaves and roots were higher in the control than in the biocontrol treatments. Salicylic acid- and Pantoea sp. HB-22-treated cucumbers showed increased expression of the acidic peroxidase-encoding gene and the phenylalanine ammonia homologue, while the P. aeruginosa HB-15 treatment did not induce an increase in expression of any of the genes studied.

Laryngoscopes: Evaluation of microbial load of blades

Laryngoscope blades were analyzed, and the presence of blood, bodily fluids, and microorganisms was verified, indicating their potential as a source of cross contamination during clinical usage. The way in which the blades are cleaned and disinfected in daily practice may place the patient and health care team at risk. The aim of this study was to determine the bacterial and fungal load on this equipment. Descriptive cross-sectional study. A total of 83 laryngoscope blades, ready for use, were analyzed for their bacterial and fungal load at 2 university hospitals. The microbiologic analysis revealed the presence of microorganisms in 76.2% of cases at institution 1 and 92.7% of cases at institution 2, with microbial loads >10(1) colony forming units in 31.2% and 44.7% of cases, respectively. At both institutions, potentially pathogenic microorganisms were found, including Candida sp, Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, extended-spectrum β-lactamase-producing Klebsiella pneumoniae, multiresistant Acinetobacter baumannii, Pantoea sp, Enterobacter gergoviae, Escherichia coli, and Proteus mirabilis. These results indicate that the use of laryngoscope blades at these 2 institutions present a potential risk. Based on these findings, action needs to be taken so a higher level of safety can be offered to patients and health care professionals who have direct contact with this equipment.

Isolation of efficient phosphate solubilizing bacteria capable of enhancing tomato plant growth

Phosphorus is one of the three macronutrients that are essential for plant growth and development. Inorganic phosphorus (P), which can make up to 70% of the total P content in soils, can exist in calcium-, aluminum-, or iron-complexed forms that are unavailable for plant use. As a result, mineral phosphorus, P2O5, is often used as a fertilizer to supplement the nutrient for crop growth. To reduce the addition of mineral phosphorus to agricultural soils, research in naturally occurring phosphate-solubilizing microorganisms has been conducted for decades. This study found bacteria that solubilized phosphate at very high rates. The most efficient of the bacteria presented in this paper, Pantoea sp. Pot1, can solubilize tricalcium phosphate (Ca3(PO4)2) at a rate of 956 mgL-1. This bacteria produces a variety of organic acids, including acetic, gluconic, formic, and propionic acids. Greenhouse experiments demonstrated that tomato plants with soil systems inoculated with Pantoea sp. Pot1 incorporated more P and produced much higher biomass weights than those plants without any added bacteria.

Raman chemical imaging of the rhizosphere bacterium Pantoea sp. YR343 and its co-culture with Arabidopsis thaliana.

Chemical imaging of plant-bacteria co-cultures makes it possible to characterize bacterial populations and behaviors and their interactions with proximal organisms, under conditions closest to the environment in the rhizosphere. Here Raman micro-spectroscopy and confocal Raman imaging are used as minimally invasive probes to study the rhizosphere bacterial isolate, Pantoea sp. YR343, and its co-culture with model plant Arabidopsis thaliana by combining enhanced Raman spectroscopies with electron microscopy and principal component analysis (PCA). The presence of carotenoid pigments in the wild type Pantoea sp. YR343 was characterized using resonance Raman scattering, which was also used to confirm successful disruption of the crtB gene in an engineered carotenoid mutant strain. Other components of the Pantoea sp. YR343 cells were imaged in the presence of resonantly enhanced pigments using a combination of surface enhanced Raman imaging and PCA. Pantoea sp. YR343 cells decorated with Ag colloid synthesized ex situ gave spectra dominated by carotenoid scattering, whereas colloids synthesized in situ produced spectral signatures characteristic of flavins in the cell membrane. Scanning electron microscopy (SEM) of whole cells and transmission electron microscopy (TEM) images of thinly sliced cross-sections were used to assess structural integrity of the coated cells and to establish the origin of spectral signatures based on the position of Ag nanoparticles in the cells. Raman imaging was also used to characterize senescent green Arabidopsis thaliana plant roots inoculated with Pantoea sp. YR343, and PCA was used to distinguish spectral contributions from plant and bacterial cells, thereby establishing the potential of Raman imaging to visualize the distribution of rhizobacteria on plant roots.

Examining phylogenetic relationships of Erwinia and Pantoea species using whole genome sequence data.

The genera Erwinia and Pantoea contain species that are devastating plant pathogens, non-pathogen epiphytes, and opportunistic human pathogens. However, some controversies persist in the taxonomic classification of these two closely related genera. The phylogenomic analysis of these two genera was investigated via a comprehensive analysis of 25 Erwinia genomes and 23 Pantoea genomes. Single-copy orthologs could be extracted from the Erwinia/Pantoea core-genome to reconstruct the Erwinia/Pantoea phylogeny. This tree has strong bootstrap support for almost all branches. We also estimated the in silico DNA-DNA hybridization (isDDH) and the average nucleotide identity (ANI) values between each genome; strains from the same species showed ANI values ≥96% and isDDH values >70%. These data confirm that whole genome sequence data provides a powerful tool to resolve the complex taxonomic questions of Erwinia/Pantoea, e.g. Pantoea agglomerans 299R was not clustered into a single group with other P. agglomerans strains, and the ANI values and isDDH values between them were <91% and around 43.8%, respectively. These data indicate P. agglomerans 299R should not be classified into the P. agglomerans species. In addition, another strain (Pantoea sp. At_9b) was identified that may represent a novel Pantoea species. We also evaluated the performance of six commonly used housekeeping genes (atpD, carA, gyrB, infB, recA, and rpoB) in phylogenetic inference. A single gene was not enough to obtain a reliable species tree, and it was necessary to use the multilocus sequence analysis of the six marker genes to recover the Erwinia/Pantoea phylogeny.

Using Raman Spectroscopy and SERS for in-situ studies of rhizosphere bacteria.

Bacteria colonize plant roots to form a symbiotic relationship with the plant and can play in important role in promoting plant growth. Raman spectroscopy is a useful technique to study these bacterial systems and the chemical signals they utilize to interact with the plant. We present a Raman study of Pantoea YR343 that was isolated from the rhizosphere of Populus deltoides (Eastern Cottonwood). Pantoea sp. YR343 produce yellowish carotenoid pigment that play a role in protection against UV radiation, in the anti-oxidative pathways and in membrane fluidity. Raman spectroscopy is used to non-invasively characterize the membrane bound carotenoids. The spectra collected from a mutant strain created by knocking out the crtB gene that encodes a phytoene synthase responsible for early stage of carotenoid biosynthesis, lack the carotenoid peaks. Surface Enhanced Raman Spectroscopy is being employed to detect the plant phytoharmone indoleacetic acid that is synthesized by the bacteria. This work describes our recent progress towards utilizing Raman spectroscopy as a label free, non-destructive method of studying plant-bacteria interactions in the rhizosphere.

Novel Glucose-1-Phosphatase with High Phytase Activity and Unusual Metal Ion Activation from Soil Bacterium Pantoea sp. Strain 3.5.1.

Phosphorus is an important macronutrient, but its availability in soil is limited. Many soil microorganisms improve the bioavailability of phosphate by releasing it from various organic compounds, including phytate. To investigate the diversity of phytate-hydrolyzing bacteria in soil, we sampled soils of various ecological habitats, including forest, private homesteads, large agricultural complexes, and urban landscapes. Bacterial isolate Pantoea sp. strain 3.5.1 with the highest level of phytase activity was isolated from forest soil and investigated further. The Pantoea sp. 3.5.1 agpP gene encoding a novel glucose-1-phosphatase with high phytase activity was identified, and the corresponding protein was purified to apparent homogeneity, sequenced by mass spectroscopy, and biochemically characterized. The AgpP enzyme exhibits maximum activity and stability at pH 4.5 and at 37°C. The enzyme belongs to a group of histidine acid phosphatases and has the lowest Km values toward phytate, glucose-6-phosphate, and glucose-1-phosphate. Unexpectedly, stimulation of enzymatic activity by several divalent metal ions was observed for the AgpP enzyme. High-performance liquid chromatography (HPLC) and high-performance ion chromatography (HPIC) analyses of phytate hydrolysis products identify dl-myo-inositol 1,2,4,5,6-pentakisphosphate as the final product of the reaction, indicating that the Pantoea sp. AgpP glucose-1-phosphatase can be classified as a 3-phytase. The identification of the Pantoea sp. AgpP phytase and its unusual regulation by metal ions highlight the remarkable diversity of phosphorus metabolism regulation in soil bacteria. Furthermore, our data indicate that natural forest soils harbor rich reservoirs of novel phytate-hydrolyzing enzymes with unique biochemical features.

Optimization and Evaluation of Biosurfactant Produced by Pantoea sp. Using Pineapple Peel Residue, Vegetable Fat and Corn Steep Liquor

Optimization and Evaluation of Biosurfactant Produced by Pantoea sp. Using Pineapple Peel Residue, Vegetable Fat and Corn Steep Liquor

Draft Genome Sequence of Pantoea sp. Strain MBLJ3, Isolated in a Laboratory Environmental Control Study.

This report describes the draft genome sequence of a newly isolated strain, Pantoea sp. MBLJ3. The genome is 4.8 Mb in size, with a G+C content of 54.27%, and it contains 4,522 protein-coding sequences, 69 tRNA genes, and 5 rRNA genes.

Cloning and characterization of 5-enopyruvylshikimate-3-phosphate synthase from Pantoea sp.

The shikimate pathway enzyme 5-enopyruvylshikimate-3-phosphate synthase (EPSPS) is the target of the broad spectrum herbicide glyphosate. A novel aroA gene encoding an EPSPS from Pantoea sp was identified and subcloned into the pET-28a vector to construct the recombinant pET-AroAPantoea sp plasmid. Amino acid sequence analysis indicated that AroAPantoea sp is a class I AroA enzyme. When expressed in Escherichia coli, it conveyed high tolerance to glyphosate. AroAPantoea sp may be used to generate transgenic glyphosate-tolerant plants.

Investigation of the internal bacterial flora of Eurygaster integriceps (Hemiptera: Scutelleridae) and pathogenicity of the flora members

Eurygaster integriceps (Hemiptera: Scutelleridae) is one of the most serious pest of wheat and other cereal crops throughout the Near and Middle East including Turkey. To contribute biological control of this pest, we investigated the culturable bacterial flora of E. integriceps and their virulence against it. We also tested different entomopathogenic fungi (Isaria fumosorosea ARSEF8356, Beauveria bassiana ARSEF8356, Metarhizium brunneum ARSEF8671 and Nomurae rileyi ARSEF1670) against this pest under laboratory conditions. Bacterial isolates were characterized based on morphological, biochemical, physiological and molecular characteristics (16S rRNA sequencing). The isolates were identified as Pantoea sp. (S1, S5, S7, S8, S10 and S11), P. agglomerans (S2, S3 and S4), Pseudomonas sp. S6 and Micrococcus luteus S9. The highest mortality within bacterial isolates was observed from Pantoea sp. S1, P. agglomerans S4 and Pantoea sp. S7 with 100%. Mortality of other bacterial species ranged from 33% to 88%. The highest mortality among the tested entomopathogenic fungi was obtained from Isaria fumosorosea ARSEF 8333 with 100%. Mortality of other fungi ranged from 33% to 50%. Consequently, Pantoea sp. S1, P. agglomerans S4, Pantoea sp. S7, Beauveria bassiana ARSEF 8356 and Isaria fumosorosea ARSEF 8356 seem to be promising candidates in the control of E. integriceps.

Characterization of the wzc gene from Pantoea sp. strain PPE7 and its influence on extracellular polysaccharide production and virulence on Pleurotus eryngii

To characterize of the pathogenicity gene from the soft rot pathogen Pantoea sp. PPE7 in Pleurotus eryngii, we constructed over 10,000 kanamycin-resistant transposon mutants of Pantoea sp. strain PPE7 by transposon mutagenesis. One mutant, Pantoea sp. NPPE9535, did not cause a soft rot disease on Pleurotus eryngii was confirmed by the pathogenicity test.The transposon was inserted into the wzc gene and the disruption of the wzc gene resulted in the reduction of polysaccharide production and abolished the virulence of Pantoea sp. strain PPE7 in P. eryngii. Analysis of the hydropathic profile of this protein indicated that it is composed of two main domains: an N-terminal domain including two transmembrane α-helices and a C-terminal cytoplasmic domain consisting of a tyrosine-rich region. Comparative analysis indicated that the amino acid sequence of Wzc is similar to that of a number of proteins involved in the synthesis or export of polysaccharides in other bacterial species. Purified GST-Wzc was found to affect the phosphorylation of tyrosine residue in vivo. These results showed that the wzc gene might play an important role in the virulence of Pantoea sp. strain PPE7 in P. eryngii.

Isolation and characterization of Cd-resistant bacteria from industrial wastewater

Three bacterial strains were isolated from industrial effluents of Penang, Malaysia. The strains RZ1, RZ2, and RZ3 were identified as Pantoea sp. RL32.2, Salmonella enterica, and Enterobacter sp. OCPSB1, respectively, based on morphological observation, biochemical, physiological characterization, and 16S rDNA sequence analysis. The strains RZ1, RZ2, and RZ3 removed 89.89, 82.10, and 89.14% of cadmium, respectively, when the 100 μg/mL of cadmium was added in the medium. The minimum inhibitory concentrations of strains RZ1, RZ2, and RZ3 were 750, 410, and 550 μg/mL, respectively. Cured strain showed resistance and sensitivity against some range of antibiotics. The molecular weights of induced proteins were 35 and 25 kDa in the presence of cadmium which points out a possible role of this protein in cadmium removal. Overall, these strains could be useful for the removal of cadmium in industrial wastewater.

OCCURRENCE OF PANTOEA BEIJINGENSIS ON PLEUROTUS ERYNGII IN CHINA

In September 2012, water-soaked lesions and soft rot of stipes and pilei were observed in China on the fruiting bodies of Pleurotus eryngii, whose growth had halted. Four bacterial isolates with yellow, smooth and convex colonies, identical morphological characters and 16S rRNA, gyrB, rpoB, infB and atpD gene sequences were isolated from diseased tissues. Molecular phylogeny based on 16S rRNA sequence and MLSA data (combined gyrB, rpoB, infB and atpD) showed that the isolates had the highest similarity with Pantoea dispersa LMG 2603T. However, physiological and biochemical tests performed using API 20 E, API 50 CHB (bioMerieux) and GN2 Microplates (Biolog), and DNA-DNA hybridization (33.9±1.3% relatedness with P. dispersa LMG 2603T), differentiated the isolates from P. dispersa, identifiying them as Pantoea beijingensis (Liu et al., 2013). Based on the 16S rRNA gene sequence, a 98% similarity was found between P. beijingensis and Pantoea sp. PA4 reported as the agent of P. eryngii soft rot in Korea (Kim et al., 2007; Liu et al., 2013), suggesting that our isolates belonged to a species differing from Pantoea sp. PA4. Bacterial suspensions (approximately 1×106 CFU/ml) inoculated on the fruiting bodies induced within 5 to 7 days symptoms similar to those observed in natural infection. Controls remained healthy. Bacterial isolates recovered from typical lesions were identical to the inoculated strains in terms of 16S rRNA gene sequence, physiological and biochemical tests, performed using API 20 E, API 50 CHB (bioMerieux) and GN2 Microplates (Biolog), thus fulfilling Koch’s postulates. P. ananatis was first reported as a pathogen of P. eryngii in Korea (Kim et al., 2007), but to the best of our knowledge, this is the first report of P. beijingensis-induced soft rot disease of P. eryngii in China.

First Report of Pantoea beijingensis Induced Soft Rot Disease of Pleurotus nebrodensis in China.

Pleurotus nebrodensis is a popular edible fungus in China. In December 2009, soft rot disease appeared on fruiting bodies of P. neberodensis in greenhouses located at Haidian District of Beijing, China. Early symptoms were water-soaked lesions on the pilei of the fruiting bodies. Lesions then spread and purulent tissues were formed. Severe soft rot induced production of deformed fruiting bodies and offensive odor. Diseased fruiting bodies stopped growth and commercial losses were estimated at 5 to 10%. Internal sections of the diseased pilei about 0.5 × 0.5 cm were suspended in 0.85% NaCl and the suspension was spread on trypticase soy agar (TSA) media. After incubation at 30°C for 2 days, dominant bacterial colonies were yellow, smooth, round, and convex. Cells were gram-negative, short rods, non-capsulated, motile, and non-spore forming. The 16S rRNA gene (1,408 bp, GenBank Accession No. KF849293) was amplified by using the universal forward primer P1 (5'-AGAGTTTGATCCTGGTCAGAACGCT-3') and the universal reverse primer P6 (5'-TACGGCTACCTTGTTACGACTTCACCCC-3'). Neighbor-joining tree analysis based on 16S rRNA gene sequences demonstrated the isolates belonged to the genus Pantoea and showed highest similarity with Pantoea beijingensis LMG 27579T (99.9% similarity, 2 base pair differences), which was isolated from the diseased fruiting bodies of P. eryngii in China. Pantoea sp. PA4, reported to be the pathogen of soft rot disease of P. eryngii in Korea (1), showed 99.8% similarity with P. ananatis ATCC 33244T, which suggested our isolates belonged to a different species with Pantoea sp. PA4 (supported by 97.9% similarity between the present isolates and Pantoea sp. PA4) (2). Results of physiological properties and enzyme activities determined by the API 20E, API 20NE, API 50CH, API ZYM (bioMérieux), and GN2 MicroPlate (Biolog) system showed that there was no difference between the present isolates and P. beijingensis LMG 27579T. Pathogenicity tests for these isolates were performed with bacterial suspensions (approximately 1 × 106 CFU/ml) that were grown for 24 h in trypticase soy broth (TSB). Fruiting bodies of P. nebrodensis were induced after spawn was run for 30 days in plastic bags. When the young fruiting bodies were forming, the prepared bacterial suspension was sprayed onto the surface of the pilei. Sterilized TSB media was used as a negative control. All inoculated fruiting bodies were then incubated at 16°C with 80 to 95% relative humidity. Assays were conducted twice and five fruiting bodies were used each time. Results were observed after 5 to 10 days of incubation. The symptoms that developed were similar to those observed in the original samples. The negative control remained symptomless. Koch's postulates were fulfilled by re-isolating bacteria, which were identical to the original isolates based on 16S rRNA gene sequence analysis, physiological properties and enzyme activities. Pantoea ananatis was first reported as a pathogen of Pleurotus eryngii, causing soft rot disease (1), but to the best of our knowledge, this is the first report of P. beijingensis- induced soft rot disease of P. nebrodensis in China. This disease may be an emerging disease problem in the near future and information on this pathogen will be useful in the development of management practices.

Combined use of Alkane-Degrading and Plant Growth-Promoting Bacteria Enhanced Phytoremediation of Diesel Contaminated soil

Inoculation of plants with pollutant-degrading and plant growth-promoting microorganisms is a simple strategy to enhance phytoremediation activity. The objective of this study was to determine the effect of inoculation of different bacterial strains, possessing alkane-degradation and 1-amino-cyclopropane-1-carboxylic acid (ACC) deaminase activity, on plant growth and phytoremediation activity. Carpet grass (Axonopus affinis) was planted in soil spiked with diesel (1% w/w) for 90 days and inoculated with different bacterial strains, Pseudomonas sp. ITRH25, Pantoea sp. BTRH79 and Burkholderia sp. PsJN, individually and in combination. Generally, bacterial application increased total numbers of culturable hydrocarbon-degrading bacteria in the rhizosphere of carpet grass, plant biomass production, hydrocarbon degradation and reduced genotoxicity. Bacterial strains possessing different beneficial traits affect plant growth and phytoremediation activity in different ways. Maximum bacterial population, plant biomass production and hydrocarbon degradation were achieved when carpet grass was inoculated with a consortium of three strains. Enhanced plant biomass production and hydrocarbon degradation were associated with increased numbers of culturable hydrocarbon-degrading bacteria in the rhizosphere of carpet grass. The present study revealed that the combined use of different bacterial strains, exhibiting different beneficial traits, is a highly effective strategy to improve plant growth and phytoremediation activity.