Pseudomonas Trivialis Research Articles

Determination of fungal and bacterial microbiota of broomrape species found in their major host plants grown in Hatay province of Türkiye

The aim of this study was to determine the fungal and bacterial microbiomes of broomrape species (Orobanche ramosa and O. crenata) encountered in their major host crops in different districts of Hatay province of Türkiye. Fungal isolates obtained from plants showing disease symptoms were identified as Rhizoctonia solani, Fusarium incarnatum, Sclerotinia sclerotiorum, Alternaria alternata, Epicoccum nigrum, Aspergillus niger and Rhizopus oryzae as a result of morphological, MALDI-TOF MS and molecular identification studies. Antagonist/plant growth promoting bacterial species such as Bacillus cereus, Bacillus megaterium, Bacillus mycoides, Bacillus weihenstephanensis, Bacillus pumilus, Bacillus putida, Bacillus simplex, Enterobacter cloacae, Glutamicibacter mysorens, Lysinibacillus sphaericus, Pseudomonas cedrina ssp. cedrina, Pseudomonas chlororaphis, Pseudomonas pseudomycoides, Pseudomonas trivialis, Pseudomonas thivervalensis, Pseudomonas umsongensis, Rhizobium radiobacter, Solibacillus silvestris, Stenotrophomonas maltophilia and Variovorax paradoxus were isolated from healthy broomrape plants and pathogenic bacterial species such as Pseudomonas cichorii, Pseudomonas corrugata, Pseudomonas marginalis and Pseudomonas mediterranea were isolated from plant samples of broomrape plants showing symptoms of disease and identified by MALDI-TOF MS analysis.

Impact of microbial milk quality on mesophilic starter culture metabolism: A metaproteomics approach

Using a metaproteomics approach, we showed that the initial milk quality impacts the proteome allocation of starter cultures used in cheese production and can be considered a fundamental source of cheese quality batch-to-batch variation. Raw milk was spiked with a highly proteolytic strain of Pseudomonas trivialis, previously isolated from raw milk, and incubated for 1, 3, and 6 days at refrigerated temperature. After incubation, the milk was heat-treated and then fermented with a mesophilic starter culture commonly used to produce Gouda-type cheeses. The development of metabolites was analyzed and a taxonomical and functional characterization of the starter culture was performed. Milk storage time impacted both the metaproteome of the starter culture, consequently affecting metabolite levels after fermentation and the level of protein expressed by the different taxa; Lactococcus protein was more abundant in samples made from milk stored longer with Pseudomonas while proteins expressed by Leuconostoc spp. decreased in abundance.

Pseudomonas allii sp. nov., a pathogen causing soft rot of onion in Japan.

Six phytopathogenic bacterial strains, MAFF 301512, MAFF 301513, MAFF 301514T, MAFF 301515, MAFF 301516 and MAFF 301517, were isolated from soft rot lesions of onion (Allium cepa L.) in Japan. The cells were Gram-reaction-negative, aerobic, non-spore-forming, motile with one or two polar flagella and rod-shaped. Analysis of their 16S rRNA gene sequences showed that they belong to the genus Pseudomonas, with the highest similarities to Pseudomonas poae DSM 14936T (99.86 %), Pseudomonas simiae OLiT (99.85 %), Pseudomonas trivialis DSM 14937T (99.79 %) and Pseudomonas extremorientalis KMM 3447T (99.79 %). Their genomic DNA G+C content was 60.9 mol% and the major fatty acids (>5 % of the total fatty acids) present were C16 : 0, summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c /C18 : 1 ω6c) and C17 : 0 cyclo. Phylogenetic and phylogenomic analyses based on the rpoD gene and whole genome sequences, respectively, demonstrated that the strains belong to the Pseudomonas fluorescens subgroup, but form a monophyletic and robust clade, with Pseudomonas azotoformans as their neighbour. Between the strains and P. azotoformans, the average nucleotide identity scores were 95.63-95.70 %, whereas the digital DNA-DNA hybridization scores of the strains against their closest relatives, including P. azotoformans, were 65.4 % or less, which are lower than the 70 % cut-off for prokaryotic species delineation. The strains were differentiated from their closest relatives by phenotypic characteristics, pathogenicity in onion and cellular fatty acid composition. The phenotypic, chemotaxonomic and genotypic data showed that the strains represent a novel Pseudomonas species, proposed to be named Pseudomonas allii sp. nov., with MAFF 301514T (=ICMP 23680T) being the type strain.

Qualitative and Quantitative Yield in the Radish Crop Through the Utilization of rhizobacteria, Pseudomonas trivialis (L) and Earthworm, Eudrilus eugenae (L).

The specific density of earthworm in soil and the microorganisms in soil are correlated with each other. The fruitful interactions among soil microorganisms and the earthworms in soil serve to orchestrate the process of improvement in the crop yield. The Pseudomonas trivialis (L) is a deleterious rhizobacterial species. This rhizobacterial species is recognized for the production of Indole Acetic Acid (IAA) (the plant growth promoting hormone). The present attempt deals with use of Pseudomonas trivialis (L) rhizobacteria in different concentrations (CFU/ml) (0; 10 6 ; 10 7 and 10 8 ) for analysis of qualitative parameters of radish, Raphanus sativus (L) in presence and in absence of earthworms. With reference to biomass above ground and total Presence of rhizobacteria, Pseudomonas trivialis (L), earthworms were found enhancing growth of the radish, Rhaphanus sativus (L), the response of presence of earthworm was found significant over the control. The biomass of radish, Rhaphanus sativus (L) below ground was also found improved. The titers of inoculum of rhizobacteria, Pseudomonas trivialis (L) was found significant for Radish biomass promoting influence in vermin-field. The present attempt reporting rhizobacterial inoculum of about 10 8 CFU/ml as the most suitable for excellent biomass production of radish, Rhaphanus sativus (L). The system of “Vermi-field with rhizobacterial population” should be utilized efficiently radish crop yield.

Pseudomonas cyclaminis sp. nov., a pathogen causing bacterial bud blight of cyclamen in Japan.

Five phytopathogenic bacterial strains, MAFF 301449T, MAFF 301450, MAFF 301451, MAFF 301452, and MAFF 301453, which were isolated from bud blight lesions of cyclamen (Cyclamen persicum Mill.) in Miyagi, Japan, were subjected to polyphasic taxonomic characterisation. The cells were Gram-reaction-negative, aerobic, non-spore-forming, motile with one to five polar flagella, and rod-shaped. Analysis of 16S rRNA gene sequences showed that they belong to the genus Pseudomonas, with Pseudomonas extremaustralis 14-3T (99.79 % sequence similarity), Pseudomonas trivialis DSM 14937T (99.79 %), Pseudomonas poae DSM 14936T (99.72 %), and Pseudomonas antarctica CMS 35T (99.72 %) as their relatives. The genomic DNA G+C content was 60.3 mol% and the major fatty acids (>5 % of the total fatty acids) were C16 : 0, summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), and C17 : 0 cyclo. Phylogenetic analysis using the rpoD gene sequences and phylogenomic analyses based on the whole genome sequences demonstrated that the strains are members of the Pseudomonas fluorescens subgroup, but form a monophyletic and robust clade separated from their relatives. Average nucleotide identity and digital DNA-DNA hybridisation analyses with the closely related Pseudomonas species corroborated their novel species status. The strains were differentiated from their relatives by phenotypic characteristics, pathogenicity towards cyclamen, cellular fatty acid composition, and whole-cell MALDI-TOF mass spectrometry profiles. Based on the phenotypic, chemotaxonomic, and genotypic data obtained, we conclude that the strains represent a novel Pseudomonas species, for which we propose the name Pseudomonas cyclaminis sp. nov.; the type strain is MAFF 301449T (=ICMP 23720T).

Dose-dependent effects of Pseudomonas trivialis rhizobacteria and synergistic growth stimulation effect with earthworms on the common radish

The complex interactions between soil microorganisms with earthworms and plants have the capability to change the plant growth and development. Pseudomonas trivialis is a broad-spectrum plant growth promoting rhizobacteria (PGPR) due to its indole-3-acetic acid (IAA) production, siderophore production, 1-aminocyclopropane-1- carboxylate (ACC) deaminase activity, and phosphate solubilization attributes. A study has been conducted to investigate the effect of P. trivialis concentration in the presence or absence of earthworms (Allolobophora caliginosa) on radish (Raphanus sativus) plants growth and development. The experiment tests the impact of three inoculation concentrations in the presence or absence of earthworms on radish growth and development. We show earthworms enhance the positive effects of P. trivialis (KF695047.1) on plant growth. P. trivialis displayed a stimulatory effect on plant growth with increasing the P. trivialis inoculum size. In the presence of P. trivialis (KF695047.1), earthworms induced a significant increase in the aboveground biomass and total biomass, but there was no effect belowground. The positive effect of earthworms increased with increasing the inoculum concentration of P. trivialis. Inoculating radish plants with a low concentration of P. trivialis led to a decrease in the root length in comparison with inoculated plants and treated with earthworms but no effect on the above-ground height. Therefore, this P. trivialis strain is a PGPR for radish at higher abundances but has a negative impact on IAA levels at lower abundances. There are synergistic effects of earthworms and P. trivialis at higher bacteria abundance when in combination, to enhance the stimulatory effect on the growth and development of R. sativus. In the presence of the earthworms, 108 CFU/mL is the threshold dose of P. trivialis at and above which a positive effect on R. sativus growth occurs.

Complete Genome Sequence of the Rhizobacterium Pseudomonas trivialis Strain IHBB745 with Multiple Plant Growth-Promoting Activities and Tolerance to Desiccation and Alkalinity

The complete genome sequence of 6.45 Mb is reported here for Pseudomonas trivialis strain IHBB745 (MTCC 5336), which is an efficient, stress-tolerant, and broad-spectrum plant growth-promoting rhizobacterium. The gene-coding clusters predicted the genes for phosphate solubilization, siderophore production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole-3-acetic acid (IAA) production, and stress response.

Environmental monitoring of bacterial contamination and antibiotic resistance patterns of the fecal coliforms isolated from Cauvery River, a major drinking water source in Karnataka, India.

The present study focuses prudent elucidation of microbial pollution and antibiotic sensitivity profiling of the fecal coliforms isolated from River Cauvery, a major drinking water source in Karnataka, India. Water samples were collected from ten hotspots during the year 2011-2012. The physiochemical characteristics and microbial count of water samples collected from most of the hotspots exhibited greater biological oxygen demand and bacterial count especially coliforms in comparison with control samples (p ≤ 0.01). The antibiotic sensitivity testing was performed using 48 antibiotics against the bacterial isolates by disk-diffusion assay. The current study showed that out of 848 bacterial isolates, 93.51% (n = 793) of the isolates were found to be multidrug-resistant to most of the current generation antibiotics. Among the major isolates, 96.46% (n = 273) of the isolates were found to be multidrug-resistant to 30 antibiotics and they were identified to be Escherichia coli by 16S rDNA gene sequencing. Similarly, 93.85% (n = 107), 94.49% (n = 103), and 90.22% (n = 157) of the isolates exhibited multiple drug resistance to 32, 40, and 37 antibiotics, and they were identified to be Enterobacter cloacae, Pseudomonas trivialis, and Shigella sonnei, respectively. The molecular studies suggested the prevalence of bla TEM genes in all the four isolates and dhfr gene in Escherichia coli and Sh. sonnei. Analogously, most of the other Gram-negative bacteria were found to be multidrug-resistant and the Gram-positive bacteria, Staphylococcus spp. isolated from the water samples were found to be methicillin and vancomycin-resistant Staphylococcus aureus. This is probably the first study elucidating the bacterial pollution and antibiotic sensitivity profiling of fecal coliforms isolated from River Cauvery, Karnataka, India.

Karakter dan Potensi Inokulum Bakteri Fosfat dalam Melepaskan Fosfor

Soil bacteria group which can release soil P-adsorbed is phosphate bacteria (PB). PB can release soil P-adsorbed through: 1) acidification, 2) chelating 3) ligand exchange 4) mineralization and 5) compete colloid sorption site. PB have a potential to release soil P-adsorbed. This study was aimed to determining the character and PB inoculant potential in soil P-adsorbed release. The results of BLASTn PB showed that isolate 1 was Pseudomonas trivialis , isolate 5 was Pseudomonas putida and isolate 9 was Pseudomonas fluorescens . Based on the growth curve on day 5 th (the end log. phase) population of Pseudomonas trivialis was 10 10 CFU/mL, Pseudomonas putida was 10 14 CFU/mL and Pseudomonas fluorescens was 10 17 CFU/mL. Storage inoculant PB population decrease 97-84 % and 80-65 % PB lowering capabilities.

N-Acyl Homoserine Lactones sebagai Signal Quorum Sensing untuk Meningkatkan Efektifitas Bakteri Fosfat

Phosphate bacteria (PB) are able to release P-adsorption by soil. PB effectiveness in releasing adsorption P controled by quorum sensing (QS) signal. PB produces a QS signal as N-acyl homoserine lactones (N-HSL). The aim of this study are to determine the type of N-HSL as QS signal of PB ( Pseudomonas trivialis, P. putida and P. fluorescens ) and find the source of N-HSL from root extracts of some plants (rice, corn, bamboo, banana and peanuts). Analysis of N-HSL using HPLC (Hitachi UV-VIS detector L-2420), L-2200 autosampler (20 mL), L-2130 pump and column C OOF-4250-CO/10 µm LaChrom Ultra 18 (2 µm) 100 A 150 x 4.60 mm 10 m KPOW 490065-1 (Phenomenex), temperature 60° C, flow rate of 0.9 mL/minute and a gradient of 30-100 % in 1.0 minutes. Standard N-HSL is C4-HSL, 6, 8, 10, 12 homoserine lactones (Sigma-Aldrich, Germany) was dissolved in acetonitrile (Merch, India) with a concentration of 50 mM. P-dissolved by PB determined by staining NVM and a spectrophotometer at a wavelength of 413 nm. PB population is determined by the OD ( optical density ) at a wavelength of 600 nm. PB populations on medium Pikovskaya influenced by PB isolates, the type of P sources and duration of incubation. N-HSL generated by PB highest is Butanoyl (C 4 ) homoserine lactones. PB isolates 9 and Ca-phosphate sources produce N-HSL most. Root extract of rice, corn, bamboo, bananas and peanuts can be a source of N-HSL. Soluble phosphorus from medium Pikovskaya influenced by the type of PB isolates and source of P.

Statistical Optimization of Medium Components for Mass Production of Plant Growth-Promoting Microbial Inoculant Pseudomonas trivialis BIHB 745 (MTCC5336).

Optimizing nutritional requirements for mass production of microbial inoculants in shortened time has relevance for their economical field application. Therefore, the present study aimed at selecting suitable growth medium, optimizing its components, and up-scaling inoculum production for plant growth-promoting Pseudomonas trivialis BIHB 745. Of the different media tested, the culture exhibited maximal viable colony count in trypticase soya broth with 17.6% increased biomass on optimizing levels of carbon source, nitrogen source, and NaCl using response surface methodology. A twofold higher biomass with 9h shorter incubation period was obtained in optimized medium in a bioreactor in comparison to shake flasks.

Alleviation of salt stress of symbiotic Galega officinalis L. (goat's rue) by co-inoculation of Rhizobium with root-colonizing Pseudomonas

Salt stress is an increasing problem in agricultural soils in many parts of the world, and salt tolerant cropping systems are in great demand. We investigated the effect of co-inoculation of Galega officinalis with Rhizobium galegae and two plant growth promoting Pseudomonas species on plant growth, nodulation, and N content under salt stress. The effect of inoculation with R. galegae sv. officinalis HAMBI 1141 alone and in combination with the root-colonizing Pseudomonas extremorientalis TSAU20 or Pseudomonas trivialis 3Re27 on the growth of G. officinalis exposed to salt stress (50 and 75 mM NaCl) was studied under gnotobiotic and greenhouse conditions. The growth of goat’s rue was reduced at 50 and 75 mM NaCl both in the gnotobiotic sand system and in low-fertilized potting soil in the greenhouse. Co-inoculation of unstressed and salt-stressed goat’s rue with R. galegae HAMBI 1141 and either P. extremorientalis TSAU20 or P. trivialis 3Re27 significantly improved root and shoot growth and increased nodulation of plant roots in both growth systems compared with plants inoculated with R. galegae alone. The nitrogen content of co-inoculated plant roots was significantly increased at 75 mM NaCl in potting soil. Co-inoculation of G. officinalis with either of the two plant growth promoting (PGPR) Pseudomonas strains also improved root tip-colonization by R. galegae cells. The co-inoculation of goat’s rue with Rhizobium and PGPR Pseudomonas strains alleviated salt stress of plants grown in NaCl-amended gnotobiotic sand systems and in potting soil in the greenhouse.

Antibacterial metabolites synthesized by psychrotrophic bacteria isolated from cold-freshwater environments

The ability of three psychrotrophic Gram-negative bacilli isolated from Chilean Patagonian cold freshwater rivers to produce bioactive metabolites was evaluated. The strains were isolated from cold waters rivers and identified by their biochemical properties and 16S rRNA gene analysis. The metabolites fractions showing antibacterial activity were obtained by solvent extraction and partially characterized by gas-mass chromatography (GC-MS). Antibacterial activity of the fractions was evaluated by an agar-well diffusion test upon 14 bacterial strains, both Gram positive and Gram negative. Thermal and proteolytic resistances of the antibacterial metabolites fractions were also evaluated. Molecular analysis allows the identification of the three Patagonian strains as Pseudomonas sp. RG-6 (Pseudomonas brenneri 99.6% identity), Pseudomonas sp. RG-8 (Pseudomonas trivialis 99.6% identity) and Yersinia sp. RP-3 (Yersinia aldovae 99.5% identity). These extracts were able to inhibit both Gram-positive and Gram-negative bacteria but not Listeria monocytogenes. The antibacterial activity of the filtrated supernatants was lost at temperatures ≥60°C, and was not affected by proteinase K treatment. The chemical structure of the active molecule remains to be elucidated, although the GC-MS analysis of the filtrates suggests that compounds like sesquiterpenes derivatives from β-maaliene or δ-selinene could be responsible of this antibacterial activity. Pristine cold freshwater streams showed to be interesting sources of metabolites-producing microorganisms with antibacterial activity.

Seleksi isolat bakteri pelarut fosfat ((BPF) untuk mengembangkan inokulum efektif

The phosphate solubilizing bacteria (PSB) can release insoluble phosphate in soil by anorganik-P dissolution, organic-P mineralization, and blocking of soil adsorption site. The selection of effective PSB, therefore, is urgently required to study the effectiveness of PSB. The research was arranged to determine: 1) P-solubi-lization or P-mineralization, 2) physiology, and 3) PSB inoculant improvement. The research was arranged in complete random design, with PSB isolate as treatment. The variables were: soluble-P, mineralize-P, adsorption-P, pH, PSB population, phosphatase and phythase activity. The result showed that PSB isolate 1 = Pseudomonas trivialis , 5 = Pseudomonas putida , and 9 = Pseudomonas fluorescens , were the best in P solubilization or P mineralization. Solubilization efficiency of isolate were 1 = 291%, 5 = 280%, and 9 = 347%. Five days incubation (the end of log phase or early of stationary phase) was the best time to culture harvest for PSB inoculant formulate. Within twelve months age of culture, population stability of PSB inoculant decreased between 81 and 88%, and P solubilizing stability PSB inoculant decrease between 65 and 81%. Decreasing of P solubility to P source types of PSB inoculant was AlP > FeP > PR > CaP.

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet

To develop effective biocontrol strategies, basic knowledge of plant growth promotion (PGP) and root colonization by antagonists is essential. The survival and colonization patterns of five different biocontrol agents against Rhizoctonia solani AG2-2IIIB in the rhizosphere of greenhouse-grown sugar beet plants were analysed in single and combined treatments. The study included bacteria (Pseudomonas fluorescens L13-6-12, Pseudomonas trivialis RE(*) 1-1-14, Serratia plymuthica 3Re4-18) as well as fungi (Trichoderma gamsii AT1-2-4, Trichoderma velutinum G1/8). Microscopic analysis by confocal laser scanning microscopy revealed different colonization patterns for each DsRed2/green fluorescent protein-labelled strain. Bacteria and T. velutinum G1/8 colonized the root surface and the endorhiza in single and co-culture, while for T. gamsii AT1-2-4, only the transfer of spores was observed. Whereas Pseudomonas strains formed large microcolonies consisting of hundreds of cells, S. plymuthica was arranged in small endophytic clusters or clouds around the entire root system. In co-culture, each strain showed its typical pattern and occupied specific niches on the root, without clear evidence of morphological interactions. PGP was only observed for four strains with rhizosphere competence and not for T. gamsii AT1-2-4. The results provide useful information on which combination of strains to test in larger biocontrol experiments directed to applications.

Biological control of great brome (Bromus diandrus) in durum wheat (Triticum durum): specificity, physiological traits and impact on plant growth and root architecture of the fluorescent pseudomonad strain X33d

The rhizobacterial strain X33d was previously shown to suppress the growth of the weed great brome (Bromus diandrus Roth.). The aim of this work was to identify X33d, characterize its physiological activities, assess its specificity on different non-target crops, and its impact on the growth and the root architecture of great brome and durum wheat (Triticum durum Desf.) grown alone and together. Based on 16S rDNA sequencing, X33d was identified as Pseudomonas trivialis. The specificity assay, performed on a mixture of soil/sand/peat, highlighted the suppressive activity of P. trivialis X33d against great brome and the promoting effect on most of the considered crops, especially durum wheat. Although the growth of durum wheat on quartz sand was unaffected, P. trivialis X33d suppressed the growth and affected the root architecture of great brome, especially when co-seeded with durum wheat. Great brome plants inoculated with X33d and co-seeded with durum wheat showed low root biomass, short root systems and low surface area, volume and number of tips. Moreover, P. trivialis X33d synthesized indole-acetic acid (IAA) that could be involved both in great brome growth suppression and durum wheat growth promotion. Our results indicate that P. trivialis X33d could be exploited as a potential biocontrol agent against great brome without affecting the durum wheat growth. These results are discussed in relation to the competitive capability of great brome towards durum wheat.

Co-inoculation of Pseudomonas spp. with Rhizobium improves growth and symbiotic performance of fodder galega ( Galega orientalis Lam.)

The effect of Rhizobium galegae alone and in combination with root colonising Pseudomonas strains on the growth of fodder galega ( Galega orientalis Lam.) was studied under greenhouse conditions in potting soil containing low levels of nitrogen. Eight weeks after sowing combined inoculations of fodder galega with R. galegae bv. orientalis HAMBI 540 and Pseudomonas trivialis 3Re27 or Pseudomonas extremorientalis TSAU20 had increased shoot and root dry matter, as compared with inoculation with R. galegae HAMBI 540 alone. Both Pseudomonas strains produced indole-3-acetic acid (IAA) in culture but R. galegae did not. While the cellulase producing strain P. trivialis 3Re27 was able to significantly increase nodule numbers and nitrogen content of the co-inoculated plants, the cellulase-negative P. extremorientalis TSAU20 showed no significant stimulation of nodule numbers and nitrogen content in roots. We conclude that P. trivialis 3Re27 improve rhizobia–legume interactions, acting as “rhizobium helper bacteria”. The production of IAA and/or cellulase by Pseudomonas strains may contribute to such a positive effect.

Stress Tolerance and Genetic Variability of Phosphate-solubilizing Fluorescent Pseudomonas from the Cold Deserts of the Trans-Himalayas

Nineteen efficient phosphate-solubilizing fluorescent Pseudomonas from the cold deserts of the trans-Himalayas were screened for stress tolerance against temperature, alkalinity, salinity, calcium salts, and desiccation. Phylogenetic analysis based on 16S rRNA gene sequencing placed these bacteria under three groups with fourteen strains in Group I including Pseudomonas trivialis and P. poae, two strains in Group II together with Pseudomonas kilonensis and P. corrugata, and three strains in Group III along with Pseudomonas jessenii and P. moraviensis. Genetic diversity assessed by ERIC and BOX-PCR revealed variability among strains belonging to the same phylogenetic groups. Cluster analysis based on the growth characteristics under regimes of different stress levels placed the strains into three distinct clusters displaying no correlation to their phylogenetic groups. Stress-tolerant strains differed in the level of decline in phosphate solubilization under increasing intensity of various stress parameters. The highest decrease occurred with 5% CaCO(3,) followed by 2.5% CaCO(3), pH 11, 5% NaCl, temperature of 37 degrees C, 40% PEG, 5% CaSO(4), 2.5% NaCl, 2.5% CaSO(4), pH 9 and temperature of 15 degrees C. Two strains belonging to Phylogenetic Group I exhibited higher phosphate solubilization at lower temperature. The results revealed that stress-tolerance ability was not limited to any particular phylogenetic group. Knowledge about the genetic variants of phosphate-solubilizing fluorescent Pseudomonas with potential for tolerance to desiccation, alkalinity, temperature, and salinity could be useful in understanding their ecological role under stressful environments of low phosphate availability.

Effect of bacterial antagonists on lettuce: active biocontrol of Rhizoctonia solani and negligible, short-term effects on nontarget microorganisms.

The aim of this study was to assess the biocontrol efficacy against Rhizoctonia solani of three bacterial antagonists introduced into naturally Rhizoctonia-infested lettuce fields and to analyse their impact on the indigenous plant-associated bacteria and fungi. Lettuce seedlings were inoculated with bacterial suspensions of two endophytic strains, Serratia plymuthica 3Re4-18 and Pseudomonas trivialis 3Re2-7, and with the rhizobacterium Pseudomonas fluorescens L13-6-12 7 days before and 5 days after planting in the field. Similar statistically significant biocontrol effects were observed for all applied bacterial antagonists compared with the uninoculated control. Single-strand conformation polymorphism analysis of 16S rRNA gene or ITS1 fragments revealed a highly diverse rhizosphere and a less diverse endophytic microbial community for lettuce. Representatives of several bacterial (Alpha-, Beta- and Gammaproteobacteria, Firmicutes, Bacteriodetes), fungal (Ascomycetes, Basidiomycetes) and protist (Oomycetes) groups were present inside or on lettuce plants. Surprisingly, given that lettuce is a vegetable that is eaten raw, species of genera such as Flavobacterium, Burkholderia, Staphylococcus, Cladosporium and Aspergillus, which contain potentially human pathogenic strains, were identified. Analysis of the indigenous bacterial and endophytic fungal populations revealed only negligible, short-term effects resulting from the bacterial treatments, and that they were more influenced by field site, plant growth stage and microenvironment.

Characterization of Phosphate-Solubilizing Fluorescent Pseudomonads from the Rhizosphere of Seabuckthorn Growing in the Cold Deserts of Himalayas

Isolation and characterization of fluorescent pseudomonads with high phosphate-solubilizing ability is reported from the alkaline and calcium-rich soils with low P availability in the cold desert region of Lahaul and Spiti in the trans-Himalayas of India. Of 216 phosphate-solubilizing isolates, 12 exhibiting high solubilization of tricalcium phosphate (TCP) in NBRIP liquid culture were identified as Pseudomonas trivialis, P. poae, P. fluorescens, and Pseudomonas spp. on the basis of phenotypic features, whole-cell fatty acids methyl ester (FAME) profiles, and 16S rDNA sequencing. These isolates also showed relatively high solubilization of North Carolina rock phosphate (NCRP) in comparison to the solubilization of Mussoorie rock phosphate (MRP) and Udaipur rock phosphate (URP). The solubilization of phosphate substrates by P. trivialis and P. poae is reported for the first time.