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1.
Sandy Sampaio Videira Michele de Cássia Pereira e Silva Péricles de Souza Galisa Armando Cavalcante Franco Dias Riitta Nissinen Vera Lúcia Baldani Divan Jan Dirk van Elsas José Ivo Baldani Joana Falcão Salles 《Plant and Soil》2013,373(1-2):737-754
Aims
Previous studies have shown that elephant grass is colonized by nitrogen-fixing bacterial species; however, these results were based on culture-dependent methods, an approach that introduces bias due to an incomplete assessment of the microbial community. In this study, we used culture-independent methods to survey the diversity of endophytes and plant-associated bacterial communities in five elephant grass genotypes used in bioenergy production.Methods
The plants of five genotypes of elephant grass were harvested from the experimental area of Embrapa Agrobiologia and divided into stem and root tissues. Total DNA and RNA were extracted from plant tissues and the bacterial communities were analyzed by DGGE and clone library of the 16S rRNA and nifH genes at both the cDNA and DNA levels.Results
Overall, the patterns based on DNA- and RNA-derived DGGE-profiles differed, especially within tissue samples. DNA-based DGGE indicated that both total bacterial and diazotrophic communities associated with roots (rhizoplane?+?endophytes) differed clearly from those obtained from stems (endophytes). These results were confirmed by the phylogenetic analyses of RNA-derived sequences of 16S rRNA (total bacteria; 586 sequences), but not for nifH (186). In fact, rarefaction analyses showed a higher diversity of diazotrophic organisms associated with stems than roots. Based on 16S rRNA sequences, the clone libraries were dominated by sequences affiliated to members of Leptotrix (12.8 %) followed by Burkholderia (9 %) and Bradyrhizobium (6.5 %), while most of the nifH clones were closely related to the genus Bradyrhizobium (26 %).Conclusions
Our results revealed an unexpectedly large diversity of metabolically active bacteria, providing new insights into the bacterial species predominantly found in association with elephant grass. Furthermore, these results can be very useful for the development of new strategies for selection of potential bacteria that effectively contribute to biological nitrogen fixation and enhance the sustainable production of elephant grass as bioenergy crop. 相似文献2.
Rafael F. de Morais Diego M. Quesada Veronica M. Reis Segundo Urquiaga Bruno J. R. Alves Robert M. Boddey 《Plant and Soil》2012,356(1-2):23-34
Aims
Because of its high dry matter (DM) productivity, elephant grass (Pennisetum purpureum) is an ideal candidate for biomass production for biofuel production if low N fertilizer rates are used to avoid high fossil fuel inputs. The objective of this study was to investigate the potential of different elephant grass genotypes to obtain contributions of plant-associated biological N2 fixation (BNF).Methods
Three field experiments with 4 or 5 different genotypes were conducted on low-fertility Acrisols, two in Rio de Janeiro State and one in Espirito Santo for the evaluation of DM and N accumulation and 15N abundance.Results
DM and N accumulation rates of four genotypes in the two experiments in Rio State stabilized at high levels after 2?years of growth. In all experiments the spontaneously-occurring weeds in the plots were significantly higher in 15N abundance than the elephant grass genotypes. The lower 15N abundance of the elephant grass was shown not to be due to lower δ15N abundance at depth in the soil.Conclusions
Four of the grass genotypes obtained between 18 and 70% of their N from BNF amounting to inputs of between 36 and 132?kg N ha?1?yr?1. 相似文献3.
Cecilia Taulé Cintia Mareque Claudia Barlocco Fernando Hackembruch Veronica M. Reis Margarita Sicardi Federico Battistoni 《Plant and Soil》2012,356(1-2):35-49
Background and aims
Rhizospheric, epiphytic and endophytic bacteria are associated with several non-legumes, colonizing their surface and inner tissues. Many of these bacteria are beneficial to their hosts, and are collectively termed plant growth-promoting rhizobacteria (PGPR). Recent interest has focused particularly upon PGPR that are endophytic (i.e. PGPE), and which have been reported to be associated with important crops such as rice, wheat and sugarcane. Different mechanisms are involved in bacteria-induced plant growth promotion (PGP), including biological nitrogen fixation (BNF), mineral solubilization, production of phytohormones and pathogen biocontrol. In Uruguay, sugarcane (Saccharum officinarum L.) is considered a strategic multipurpose crop, used for bioenergy, feed, sugar and bioethanol production. The aim of this work was to estimate the BNF contribution to Uruguayan sugarcane cultivars, as well as to identify and characterize the (culturable) putatively endophytic diazotrophic bacteria associated with these varieties.Methods and results
Results using the 15N-dilution technique have shown that these sugarcane varieties obtain significant inputs of N from BNF (34.8–58.8% Ndfa). In parallel, a collection of 598 isolates of potentially endophytic diazotrophs was obtained from surface-sterilized stems using standard isolation techniques, and nifH + isolates from these were the subject of further studies. The bacteria were shown to belong to several genera, including Pseudomonas, Stenotrophomonas, Xanthomonas, Acinetobacter, Rhanella, Enterobacter, Pantoea, Shinella, Agrobacterium and Achromobacter. Additionally, some PGP features were studied in 35 selected isolates. The data obtained in this study represent the initial steps in a program aimed at determining the mechanisms of PGP of non-legume crops in Uruguay (such as sugarcane) with potentially beneficial plant-associated bacteria. 相似文献4.
German Andres Estrada Vera Lúcia Divan Baldani Danilo Messias de Oliveira Segundo Urquiaga José Ivo Baldani 《Plant and Soil》2013,369(1-2):115-129
Background and Aims
Plant growth-promoting bacteria, mainly diazotrophs and phosphate solubilizers, can reduce the use of chemical fertilizers for rice crops. Here, diazotrophic bacteria isolated from rice were screened for their ability to solubilize inorganic P (Pi) in vitro and in association with rice plants cultivated in pots.Methods
Forty-nine isolates were tested for the ability to solubilize Pi on NBRIP and GL agar plate media and seven selected strains were further evaluated in NBRIP liquid medium. Three of these strains were inoculated in rice plants grown in soil pots containing 15N-labeled fertilizer and two sources of P: tricalcium phosphate (TCP) or simple superphosphate (SSP). The dry matter, yield, N, P, and the 15N content accumulated in plant tissues were measured at 135 days after planting.Results
Seven strains belonging to the genera Herbaspirillum and Burkholderia formed a halo of solubilized Pi on agar plates. The Burkholderia strains showed peak soluble P (around 200 mg P L?1) on the fifth day when grown in NBRIP liquid medium for 14 days. Inoculation of Herbaspirillum strains (H18, ZA15) and a Burkholderia vietaminensis strain (AR114) increased rice grain yield from 33 to 47 % with TCP and 18 to 44 % with TSS, respectively. The bacterial inoculation led to enhanced N-use efficiency of the 15N-labeled fertilizer.Conclusion
These results suggest that the selection and use of P-solubilizing diazotrophic bacteria are a good strategy to promote P solubilization and/or N use efficiency in rice plants. 相似文献5.
A combination of humic substances and Herbaspirillum seropedicae inoculation enhances the growth of maize (Zea mays L.) 总被引:1,自引:0,他引:1
Luciano Pasqualoto Canellas Dariellys Martínez Balmori Leonardo Oliveira Médici Natália Oliveira Aguiar Eliemar Campostrini Raul C. C. Rosa Arnoldo R. Façanha Fábio Lopes Olivares 《Plant and Soil》2013,366(1-2):119-132
Background
Endophytic diazotrophic bacteria colonize several non-leguminous plants and promote plant growth. Different mechanisms are involved in bacteria-induced plant growth promotion, including biological nitrogen fixation (BNF), mineral solubilization, production of phytohormones, and pathogen biocontrol. Herbaspirillum seropedicae is a broad-host-range endophyte that colonizes sugarcane, rice, wheat, sorghum, and maize, and has been used as a biofertilizer. Contrasting results between greenhouse and field experiments have prompted efforts to improve the consistency of the plant response to microbial stimulation.Aims
The aim of this study was to evaluate the effect of the presence of humic substances on inoculation of maize (Zea mays L.) with H. seropedicae.Methods
Two experiments were conducted: one in the greenhouse using sand and nutrient solution and the other a field trial in soil with low natural fertility and to which was applied N in the form of urea (50 kg ha?1). In the greenhouse, pre-emerging seeds were inoculated with a solution of H. seropedicae (109 cells mL?1) in the presence of humic substances isolated from vermicompost (10, 20, or 30 mg C?L?1); in the field trial, bacteria combined with humate were added as a foliar spray (450 L?ha?1).Results
At early stages (7 and 45 days old) in the greenhouse, the treatment activated plant metabolism including enhancement of plasma membrane H+-ATPase activity, alteration of sugar and N metabolism, and greater net photosynthesis. The number of viable bacterial cells was higher in root tissues when inoculation was in the presence of soluble humic substances. Foliar application of endophytic diazotrophic bacteria and humic substances increased maize grain production 65 % under field conditions. These results show a promising use of humic substances to improve the benefit of endophytic diazotrophic inoculation. 相似文献6.
In vitro generation of somaclonal variant plants of sugarcane for tolerance to Fusarium sacchari 总被引:1,自引:0,他引:1
Tendekai Mahlanza R. Stuart Rutherford Sandy J. Snyman M. Paula Watt 《Plant cell reports》2013,32(2):249-262
Key message
A combination of in vitro culture and mutagenesis using ethyl methanesulfonate (EMS) followed by culture filtrate-mediated selection produced variant sugarcane plants tolerant and resistant to Fusarium sacchari.Abstract
Eldana saccharina is a destructive pest of the sugarcane crop in South Africa. Fusarium sacchari PNG40 (a fungal strain harmful to E. saccharina) has the potential to be an endophytic biological control agent of the stalk borer. However, the fungus causes Fusarium stalk rot in sugarcane. In the current study, sugarcane plants tolerant and resistant to F. sacchari PNG40 were produced by exposing embryogenic calli to the chemical mutagen ethyl methanesulfonate (EMS), followed by in vitro selection during somatic embryogenesis and plantlet regeneration on media containing F. sacchari culture filtrates (CF). The incorporation of 100 ppm CF in the culture media at the embryo maturation stage, at germination, or at both, resulted in callus necrosis and consequent reduced plantlet yield. Subsequent trimming of the roots of regenerated plants and their exposure to 1,500 ppm CF served as a further selection treatment. Plants produced from EMS-treated calli displayed improved root re-growth in the presence of CF pressure compared with those from non-treated calli. The tolerance of CF-selected plants was confirmed in greenhouse tests by inoculation with F. sacchari PNG40, re-isolation of Fusarium spp. from undamaged tissue of asymptomatic plants and establishment of the identity of fungal isolates as PNG40 using molecular analysis. The restriction of PNG40 presence to the inoculation lesion in some plants suggested their resistance to the fungus. Genotypes exhibiting symptomless endophytic colonization by PNG40 were identified and will be utilised for testing biological control strategies against E. saccharina. 相似文献7.
Aims
Sweet potato (Ipomoea batatas) is known for its ability to grow under nitrogen-limited conditions. To clarify the possible contribution of biological nitrogen fixation, we tried to isolate and identify diazotrophic bacteria from sweet potatoes.Methods
By using cultivation technique, we isolated putative endophytes, which possess nifH genes, from surface-sterilized sweet potatoes. Their nitrogen-fixing abilities were demonstrated by the acetylene reduction assay in a semi-solid malate medium and sweet potato extracts. We also examined the colonization of an isolated strain (AT1) in sweet potatoes and their influence on growth and nitrogen fixation in plants as assessed by an acetylene reduction assay and 15N-isotope dilution technique.Results
The isolates were identified as strains of Bradyrhizobium sp. AT1, Paenibacillus sp. AS2 and Pseudomonas sp. T16 based on their 16S rRNA gene sequences. They showed acetylene reduction activity (ARA) in the semi-solid malate medium. Among them, B. sp. AT1 showed ARA in sweet potato extracts under micro-aerobic conditions whereas both P. sp. AS2 and P. sp. T16 showed no ARA. The inoculation of B. sp. AT1 to the sweet potatoes resulted in increases in the fresh weights and detection of ARA in the inoculated plants. Moreover, the reduction of 15N atom % was observed in the inoculated plants compared to uninoculated controls.Conclusions
B. sp. AT1 actively expresses nitrogenase activity in sweet potatoes and may contribute to the nitrogen nutrition of host plants. 相似文献8.
Jéssica Fernanda da Silva Thaise Rosa da Silva Indra Elena Costa Escobar Ana Carla Resende Fraiz Jonnathan Whiny Moraes dos Santos Tailane Ribeiro do Nascimento João Marcos Rodrigues dos Santos Samuel James Windsor Peters Roseli Freire de Melo Diana Signor Paulo Ivan Fernandes-Júnior 《World journal of microbiology & biotechnology》2018,34(12):186
Sorghum [Sorghum bicolor (L.) Moench] is a multipurpose grass cultivated in drylands due to its adaptation to drought. However the characteristics of sorghum-associated bacteria are not known in the Brazilian drylands. The aim of this study was to isolate and evaluate the plant growth promotion potential bacteria from field-grown sorghum under two irrigation and manure application levels in a Brazilian semi-arid reagion. Sorghum was irrigated with 3 or 1 mm day?1 and fertilized or not with liquid goat manure. Bacteria were obtained from surface-disinfected roots applying two nitrogen-free semi-solid media. The bacteria were evaluated for the presence of nifH gene, 16S rRNA sequences, calcium-phosphate solubilization, production of auxins and siderophores and for sorghum growth promotion. We obtained 20 out of 24 positive bacteria for nifH. The isolates were classified as in six different genera. All isolates produced auxins “in vitro”, six bacteria produced siderophores and three Enterobacteriaceae solubilized calcium-phosphate. At least ten bacteria resulted in the increased total N content in the sorghum shoots, comparable to fertilization with 50 mg N plant?1 week?1 and to inoculation with Azospirillum brasilense Ab-V5. Enterobacter sp. ESA 57 was the best sorghum plant-growth promoting bacteria isolated in this study. 相似文献
9.
Background and Aims
The role and linkage of endophytic bacteria to resistance of peanut seeds to biotic stress is poorly understood. The aims of the present study were to survey the experimental (axenic) and control (conventional) peanut plants for the predominant endophytic bacteria, and to characterize isolates with activity against selected A. flavus strains.Methods
Young axenic plants were grown from presumably bacteria-free embryos in the lab, and then they were grown in a field. Endophytic bacterial species were identified by the analysis of DNA sequences of their 16S-ribosomal RNA gene. DNA extracted from soil was also analyzed for predominant bacteria.Results
Mature seeds from the experimental and control plants contained several species of nonpathogenic endophytic bacteria. Among the eight bacterial species isolated from seeds, and DNA sequences detected in soil, Bacillus thuringiensis was dominant. All B. amyloliquefaciens isolates, the second abundant species in seeds demonstrated activity against A. flavus. This effect was not observed with any other bacterial isolates. There was no significant difference in number and relative occurrence of the two major bacterial species between the experimental and conventionally grown control seeds.Conclusion
Endophytic bacterial colonization derives from local soil and not from the seed source, and the peanut plant accommodates only selected species of bacteria from diverse soil populations. Some bacterial isolates showed antibiosis against A. flavus. 相似文献10.
11.
Marciel Redin René Guénon Sylvie Recous Raquel Schmatz Luana Liberalesso de Freitas Celso Aita Sandro José Giacomini 《Plant and Soil》2014,375(1-2):205-214
Background and aims
Plant growth-promoting rhizobacteria (PGPR) have been widely studied for agricultural applications. One aim of this study was to isolate cadmium (Cd)-tolerant bacteria from nodules of Glycine max (L.) Merr. grown in heavy metal-contaminated soil in southwest of China. The plant growth-promoting (PGP) traits and the effects of the isolate on plant growth and Cd uptake by legume and non-legume plants in Cd-polluted soil were investigated.Methods
Cd-tolerant bacteria were isolated by selective media. The isolates were identified by 16S rRNA gene and phylogenetic analysis. The PGR traits of the isolates were evaluated in vitro. Cd in soil and plant samples was determined by ICP-MS.Results
One of the most Cd-tolerant bacteria simultaneously exhibited several PGP traits. Inoculation with the PGPR strain had positive impacts on contents of photosynthesis pigments and mineral nutrients (Fe or Mg) in plant leaves. The shoot dry weights of Lolium multiflorum Lam. increased significantly compared to uninoculated control. Furthermore, inoculation with the PGPR strain increased the Cd concentrations in root of L. multiflorum Lam. and extractable Cd concentrations in the rhizosphere, while the Cd concentrations in root and shoot of G. max (L.) Merr. significantly decreased.Conclusions
This study indicates that inoculation with Cd-tolerant PGPR can alleviate Cd toxicity to the plants, increase Cd accumulation in L. multiflorum Lam. by enhancing Cd availability in soils and plant biomass, but decrease Cd accumulation in G. max (L.) Merr. by increasing Fe availability, thus highlighting new insight into the exploration of PGPR on Cd-contaminated soil. 相似文献12.
Survival of endophytic bacteria in polymer-based inoculants and efficiency of their application to sugarcane 总被引:1,自引:0,他引:1
Marinete Flores da Silva Cecília de Souza Ant?nio Paulo Jansen de Oliveira Gustavo Ribeiro Xavier Norma Gouvêa Rumjanek Luis Henrique de Barros Soares Veronica Massena Reis 《Plant and Soil》2012,356(1-2):231-243
Background & aims
Studies have been conducted to evaluate maintenance of cell viability and stability, as well as to select cheap carriers to extend the shelf life of plant beneficial bacterial inoculants for agricultural crops. The purpose of this study was to evaluate the shelf life and the colonization efficiency of novel liquid and gel-based inoculant formulations for sugarcane. The different inoculant formulations were all composed of a mixture of five strains of diazotrophic bacteria (Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, H. rubrisubalbicans, Azospirillum amazonense and Burkholderia tropica), which are recognized as sugarcane growth promoters.Methods
Different inoculant formulations containing as carrier the polymers carboxymethylcellulose (CMC) and corn starch (60/40 ratio) at five different concentrations (named PIC, for Polymeric Inoculant Carrier) were supplemented, or not, with 2?% MgO, an interfacial stabilizing agent. Bacterial survival in the different formulations during storage was evaluated under controlled conditions, and two experiments with mini-cuttings of sugarcane variety RB72454 were carried out under greenhouse conditions.Results
Laboratory tests showed that in the formulation composed of 0.8?g of the polymeric mixture per 100?g of the final product (PIC 0.8), survival of G. diazotrophicus and A. amazonense was around 109?CFU?mL?1 after 120?days of storage, regardless of the supplementation with MgO. The other formulation (2.2?g of polymeric mixture, PIC 2.2) presented survival levels of 108?CFU?mL?1 for up to 60?days of storage for all the individual strains. In the greenhouse, sugarcane seedlings showed a positive growth response 50?days after inoculation when inoculated with the mixture of five bacteria, with and without PIC 2.2.Conclusions
The polymer carriers described here allowed for the long-term survival of the five different bacterial strains tested. In addition, short-term experiments in the greenhouse showed that their application as part of an inoculant on sugarcane cuttings was at least as effective in terms of bacterial colonization and the promotion of plant growth as that of the bacterial mixture without carriers. 相似文献13.
Background
Sulphadoxine and pyrimethamine are anti-folate drugs that show synergistic anti-malarial effect. Point mutations in dihydrofolate reductase (dhfr) and dihydropteorate synthatase (dhps) cause anti-folate drug resistance phenotype in human malaria parasites. This study presents pattern of point mutations in dhfr/dhps genes among Indian sub-continent.Methods
Microscopically diagnosed one hundred Plasmodium vivax field isolates were collected from five widely separated geographical regions of India. Dhfr and dhps genes were PCR amplified and sequenced. Previously published mutations data were collected and analyzed using Chi square test to identify geographical cluster of mutant/wild type genotypes.Results
Sequence analysis revealed single (S58R), double (S58R/S117N) and quadruple (F57L/S58R/T61M/S117T/) point mutations at dhfr and single (A383G) to double (A383G/A553G) mutations at dhps in P. vivax field isolates. In addition, three new mutations were also observed at dhfr. Both, dhfr and dhps genes revealed tandem repeat variations in field isolates. Dhps revealed very low mutation frequency (14.0%) compared to dhfr (50.70%). Comparative analysis revealed a progressive increase in frequency of quadruple mutant dhfr genotype (p < 0.001) within five years in north-eastern state (Kamrup, Assam). Frequency of dhfr genotypes revealed three distinct geographical clusters of wild (northern India), double mutant (southern India), and quadruple mutant (north-eastern and island regions of India) on the Indian sub-continent.Conclusion
Study suggests that SP may be susceptible to P. vivax in India, except Andaman and north-eastern state. The distinction of geographical regions with sensitive and resistant parasite phenotypes would be highly useful for designing and administering national anti-malarial drug policy. 相似文献14.
Jun Jie Zhang Kai Lou Xiang Jin Pei Hong Mao En Tao Wang Chang Fu Tian Xin Hua Sui Wen Feng Chen Wen Xin Chen 《Plant and Soil》2012,353(1-2):123-134
Background and aims
Rhizobia associated with chickpea in the main chickpea production zone of Xinjiang, China have never been investigated. Here, we present the first systematic investigation of these rhizobia’s genetic diversity and symbiotic interactions with their host plant.Methods
Ninety-five isolates obtained from chickpea nodules in eight alkaline-saline (pH?8.24–8.45) sites in Xinjiang were characterized by nodulation test, symbiotic gene analysis, PCR-based restriction fragment length polymorphism (RFLP) of the 16S rRNA gene and 16S–23S rRNA intergenic spacer (IGS), BOX-PCR, phylogenies of 16S rRNA and housekeeping genes (atpD, recA and glnII), multilocus sequence analysis (MLSA) and DNA–DNA hybridization.Results
All 95 isolates were identified within the genus of Mesorhizobium. Similarities less than 96.5% in MLSA and DNA–DNA hybridization values (<50%) between the new isolates and the defined Mesorhizobium species, and high similarities (>98%) of symbiotic genes (nodC and nifH) with those of the well studied chickpea microsymbioints Mesorhizobium ciceri and Mesorhizobium mediterraneum were found.Conclusions
Chickpea rhizobia in alkaline-saline soils of Xinjiang, China, form a population distinct from the defined Mesorhizobium species. All these chickpea rhizobia in Xinjiang harbored symbiotic genes highly similar to the type strains of two well-studied chickpea rhizobia, M. ciceri and M. mediterraneum, evidencing the possible lateral transfer of symbiotic genes among these different rhizobial species. On the other hand, chickpea may strongly select rhizobia with a unique symbiotic gene background. 相似文献15.
Background
Diverse aquatic microorganisms are capable of colonizing living and non-living surfaces leading to the formation of biofilms. Commonly visualized as a slimy layer, these biofilms are filled with hundreds of other microorganisms compared to free living planktonic cells. Microbial surface colonization and surface-associated metabolic activities also exert several macroscale deleterious effects, including biofouling, biocorrosion and the persistence and transmission of harmful or pathogenic microorganisms and virulence determinants. The present study deals with the isolation and screening of marine bacteria for biofilm formation. The screened isolates were characterized and identified as Pychrobacter celer, Pychrobacter alimentarius and Kocuria rhizophila by 16S rRNA sequencing.Methods
Biofilm forming bacteria were isolated by spread plate technique and subjected to screening by microtiter plate assay. The potent biofilm formers were identified by molecular characterization using 16S rRNA gene sequencing.Results
Twelve bacterial isolates were obtained by pour plate technique and subjected to biofilm assay. Among the 12 isolates three isolates which showed maximum biofilm formation were subjected to molecular characterizationby 16S rRNA gene sequencing method. The isolates were identified as Pychrobacter celer, Pychrobacter alimentarius and Kocuria rhizophila. The EPS produced by the three biofilm forming bacteria was extracted and the protein and carbohydrate content determined.Conclusion
Among the isolates screened, isolate 8 (Kocuria rhizophila) produced maximum protein and carbohydrate which was also in accordance with the results of microtiter plate assay.16.
Adriana Ambrosini Anelise Beneduzi Thais Stefanski Felipe G. Pinheiro Luciano K. Vargas Luciane M. P. Passaglia 《Plant and Soil》2012,356(1-2):245-264
Background and Aims
This study was aimed at assessing the diversity of putatively diazotrophic rhizobacteria associated with sunflower (Helianthus annuus L.) cropped in the south of Brazil, and to examine key plant growth promotion (PGP) characteristics of the isolates for the purposes of increasing plant productivity.Methods
299 strains were isolated from the roots and rhizosphere of sunflower cultivated in five different areas using N-free media. 16S rDNA PCR-RFLP and 16S rRNA partial sequencing were used for identification and the Shannon index was used to evaluate bacterial diversity. Production of siderophores and indolic compounds (ICs), as well phosphate solubilization activities of each isolate were also evaluated in vitro. On the basis of multiple PGP activities, eight isolates were selected and tested for their N-fixation ability, and their capacity as potential PGPR on sunflower plants was also assessed.Results
All except three Gram-positive strains (phylum Actinobacteria) belonged to the Gram-negative Proteobacteria subgroups [Gamma (167), Beta (78), and Alpha (50)] and the family Flavobacteriaceae (1)]. Shannon indexes ranged from 0.96 to 2.13 between the five sampling sites. Enterobacter and Burkholderia were the predominant genera isolated from roots and rhizosphere, respectively. Producers of siderophores and ICs were widely found amongst the isolates, but only 19.8% of them solubilized phosphate. About 8% of the isolates exhibited all three PGP traits, and these mostly belonged to the genus Burkholderia. Four isolates were able to stimulate the growth of sunflower plants under gnotobiotic conditions.Conclusions
Enterobacter and Burkholderia were the dominant rhizospheric bacterial genera associated with sunflower plants. Inoculation with isolates belonging to the genera Achromobacter, Chryseobacterium, Azospirillum, and Burkholderia had a stimulatory effect on plant growth. 相似文献17.
Sumera Afzal Khan Muhammad Hamayun Hyeokjun Yoon Ho-Youn Kim Seok-Jong Suh Seon-Kap Hwang Jong-Myeong Kim In-Jung Lee Yeon-Sik Choo Ung-Han Yoon Won-Sik Kong Byung-Moo Lee Jong-Guk Kim 《BMC microbiology》2008,8(1):1-10
Background
Lamivudine is an oral nucleoside analogue widely used for the treatment of chronic hepatitis B. The main limitation of lamivudine use is the selection of resistant mutations that increases with time of utilization. Hepatitis B virus (HBV) isolates have been classified into eight genotypes (A to H) with distinct geographical distributions. HBV genotypes may also influence pathogenic properties and therapeutic features. Here, we analyzed the HBV genotype distribution and the nature and frequency of lamivudine resistant mutations among 36 patients submitted to lamivudine treatment for 12 to 84 months.Results
Half of the patients were homosexual men. Only 4/36 (11%) patients were HBV DNA negative. As expected for a Brazilian group, genotypes A (24/32 positive individuals, 75%), D (3/32, 9.3%) and F (1/32, 3%) were present. One sample was from genotype C, which is a genotype rarely found in Brazil. Three samples were from genotype G, which had not been previously detected in Brazil. Lamivudine resistance mutations were identified in 20/32 (62%) HBV DNA positive samples. Mean HBV loads of patients with and without lamivudine resistance mutations were not very different (2.7 × 107 and 6.9 × 107 copies/mL, respectively). Fifteen patients showed the L180M/M204V lamivudine resistant double mutation. The triple mutant rt173V/180M/204V, which acts as a vaccine escape mutant, was found in two individuals. The three isolates of genotype G were entirely sequenced. All three showed the double mutation L180M/M204V and displayed a large genetic divergence when compared with other full-length genotype G isolates.Conclusion
A high (55%) proportion of patients submitted to long term lamivudine therapy displayed resistant mutations, with elevated viral load. The potential of transmission of such HBV mutants should be monitored. The identification of genotypes C and G, rarely detected in South America, seems to indicate a genotype distribution different to that observed in non treated patients. Disparities in routes of transmission (genotype G seems to be linked to homosexual behavior) and in pathogenic properties (genotype C is very aggressive) among HBV genotypes may explain the presence of rare genotypes in the present work. 相似文献18.
Sheng Qin Yue-Ji Zhang Bo Yuan Pei-Yuan Xu Ke Xing Jun Wang Ji-Hong Jiang 《Plant and Soil》2014,374(1-2):753-766
Background and aims
Many plant growth-promoting endophytes (PGPE) possessing 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity can reduce the level of stress ethylene and assist their host plants cope with various biotic and abiotic stresses. However, information about the endophytic bacteria colonizing in the coastal halophytes is still very scarce. This study aims at isolating efficient ACC deaminase-producing plant growth-promoting (PGP) bacterial strains from the inner tissues of a traditional Chinese folk medicine Limonium sinense (Girard) Kuntze, a halophyte which has high economic and medicinal values grown in the coastal saline soils. Their PGP activity and effects on host seed germination and seedling growth under salinity stress were also evaluated.Methods
A total of 126 isolates were obtained from the surface sterilized roots, stems and leaves of L. sinense (Girard) Kuntze. They were initially selected for their ability to produce ACC deaminase as well as other PGP properties such as production of indole-3-acetic acid (IAA), N2-fixation, and phosphate-solubilizing activities and subsequently identified by the 16S rRNA gene sequencing. For selected strains, seed germination, seedling growth, and flavonoids production in axenically growth L. sinense (Girard) Kuntze seedlings at different NaCl concentrations (0–500 mM) were quantified.Results
Thirteen isolates possessing ACC deaminase activity were obtained. The 16S rRNA gene sequencing analysis showed them to belong to eight genera: Bacillus, Pseudomonas, Klebsiella, Serratia, Arthrobacter, Streptomyces, Isoptericola, and Microbacterium. Inoculation with four of the selected ACC deaminase-producing strains not only stimulated the growth of the host plant but also influenced the flavonoids accumulation. All four strains could colonize and can be re-isolated from the host plant interior tissues.Conclusions
These results demonstrate that ACC deaminase-producing habitat-adapted symbiotic bacteria isolated from halophyte could enhance plant growth under saline stress conditions and the PGPE strains could be appropriate as bioinoculants to enhance soil fertility and protect the plants against salt stress. 相似文献19.
Annette A. Angus Andrew Lee Michelle R. Lum Maya Shehayeb Reza Hessabi Nancy A. Fujishige Shailaja Yerrapragada Stephanie Kano Nannie Song Paul Yang Paulina Estrada de los Santos Sergio M. de Faria Felix D. Dakora George Weinstock Ann M. Hirsch 《Plant and Soil》2013,369(1-2):543-562
Background and aims
Burkholderia tuberum STM678T was isolated from a South African legume, but did not renodulate this plant. Until a reliable host is found, studies on this and other interesting beta-rhizobia cannot advance. We investigated B. tuberum STM678T’s ability to induce Fix+ nodules on a small-seeded, easy-to-propagate legume (Macroptilium atropurpureum). Previous studies demonstrated that B. tuberum elicited either Fix- or Fix+ nodules on siratro, but the reasons for this difference were unexplored.Methods
Experiments to promote effective siratro nodule formation under different environmental conditions were performed. B. tuberum STM678T’s ability to withstand high temperatures and desiccation was checked as well as its potential for promoting plant growth via mechanisms in addition to nitrogen fixation, e.g., phosphate solubilization and siderophore production. Potential genes for these activities were found in the sequenced genomes.Results
Higher temperatures and reduced watering resulted in reliable, effective nodulation on siratro. Burkholderia spp. solubilize phosphate and produce siderophores. Genes encoding proteins potentially involved in these growth-promoting activities were detected and are described.Conclusions
Siratro is an excellent model plant for B. tuberum STM678T. We identified genes that might be involved in the ability of diazotrophic Burkholderia species to survive harsh conditions, solubilize phosphate, and produce siderophores. 相似文献20.
Peter E Meissner Germain Mandi Boubacar Coulibaly Steffen Witte Théophile Tapsoba Ulrich Mansmann Jens Rengelshausen Wolfgang Schiek Albrecht Jahn Ingeborg Walter-Sack Gerd Mikus Jürgen Burhenne Klaus-Dieter Riedel R Heiner Schirmer Bocar Kouyaté Olaf Müller 《Malaria journal》2006,5(1):1-5