Identification and characterization of native rhizobia from three mungbean varieties

Aims@#Native rhizobia from root nodules of mungbean could reduce atmospheric nitrogen to ammonia for assimilation. The objective of this study was to find the best native rhizobium from mungbean. @*Methodology and results@#Three rhizobia isolates from three mungbean varieties (Maejo 3, Khampangsan 2 and Chainat 72) were collected from 10 undamaged fresh nodules at Prince Chakrabandh Pensiri Center for Plant Development, Saraburi Province, Thailand in 2016. 16S rDNA analysis identified the three rhizobia isolates as Bradyrhizobium sp. (SB1), Bradyrhizobium elkanii (SB2) and Rhizobium sp. (SB3). All the isolates could grow well in yeast mannitol agar (YMA) at pH 7, and all isolates could tolerate up to 35 °C, with isolate SB3 tolerate up to 45 °C. Isolate SB2 produced the highest amount of indole acetic acid (IAA; 8.37 mg/L) and had the highest phosphate solubilization index (7.60 SI). In a Leonard jar trial, inoculation with isolate SB2 resulted in the highest shoot fresh and dry biomass of mungbean host. Further, the mungbean inoculated with SB2 had the highest number of root nodules, nodule fresh dry weight, chlorophyll content index, and shoot and root nitrogen contents. @*Conclusion, significance and impact of study@#This study suggested that the strain SB2 (B. elkanii) is a suitable bioinoculant to improve mungbean growth and yield.

Seed size influences the promoting activity of rhizobia on plant growth, nodulation and N fixation in lima bean / O tamanho da semente influencia a atividade promotora dos rizóbios sobre o crescimento de plantas, nodulação e fixação de N em feijão-fava

ABSTRACT: This study evaluated the activity of rhizobia isolates inoculated in large (18 mm) and small (11 mm) seeds on lima bean growth, nodulation and N fixation. Selected rhizobia isolates were compared with a reference strain CIAT899 and two controls without inoculation. Large seeds contributed for highest plant growth, nodulation and N fixation than small seeds. The isolates UFPI-59, UFPI-18 and UFPI-38 promoted the highest values of shoot and root dry weight, respectively. The isolates UFPI-32 promoted the highest values of nodule number, while UFPI-59 promoted the highest values of nodule dry weight. The isolates UFPI-38 and UFPI-59 promoted the highest accumulation of N. This study showed that seed size really influences lima bean growth, nodulation and BNF. Considering rhizobia isolates, UFPI-59, UFPI-38, and UFPI-18 contributed for plant growth, promoted better nodulation and effectiveness on biological N fixation.

RESUMO: Este estudo avaliou a atividade de isolados de rizóbios inoculados em sementes pequenas (11 mm) e grandes (18 mm) sobre o crescimento, nodulação e fixação de N de feijão-fava. Isolados selecionados de rizóbios foram comparados com uma estirpe de referência CIAT899 e dois controles sem inoculação. Sementes grandes contribuíram para maior crescimento de plantas, nodulação e fixação de N do que sementes pequenas. Os isolados UFPI-59, UFPI-18 e UFPI-38 promoveram os maiores valores de massa seca de parte aérea e raízes. Os isolados UFPI-32 e UFPI-59 promoveram os maiores valores de número e massa de nódulos, respectivamente. Os isolados UFPI-38 e UFPI-59 promoveram maior acúmulo de N. Este estudo mostrou que o tamanho de sementes influencia o crescimento, nodulação e fixação de N em feijão-fava. Considerando os isolados de rizóbios, UFPI-59, UFPI-38 e UFPI-18 contribuíram para o crescimento de plantas, promoveram melhor nodulação e eficiência na fixação de N.

Microorganisms in Biostimulants

In March 2016, the EU Commission presented a proposal for new regulations on fertilising material. The regulation includes product rules for a wide range of organic and inorganic products. Microbial biostimulants is one of the categories of products that are included. Biostimulants, in the draft EU regulation, are defined as fertilising materials that affect nutrient processes independently of the product's own nutrient content and with the purpose of improving nutrient utilisation, tolerance for abiotic stress or quality of the crop. Positive list in which species of these bacterial genera are listed: Azotobacter spp, Rhizobium spp., Azospirillum spp and Mycorrhizal fungi are a part of the regulation. Since the import and use of these organisms are the responsibility of both the Norwegian Food Safety Authority and the Norwegian Environment Agency, they asked VKM to submit a joint report on effects on health (humans, plants and animals), biodiversity and dispersal, quality of agricultural land and on soil environment. Conclusions: Health risks: Based upon our literature review, we have found no indication of any specific diseases in plants, animals or humans induced by the discussed microorganisms. A few reported cases of human disease are caused through wound infections or injections in immunocompromised patients. These represent a situation where any microorganism may induce infections and is not specific for the agents discussed in this report. In summary, the risk of any disease caused by the discussed microorganisms is considered negligible. Environmental risks: In soil the biodiversity, competition, adaptation and functional redundancy of microorganisms are extremely high. This means that introduced microorganisms have a very small chance for establishing, and even less so for affecting biodiversity and soil functioning. Introduction of nitrogen fixing species or fungi that can transport P to plants (mycorrhiza) will lead to an increase in the primary production. However, even a large increased activity for these processes will not outcompete naturally occurring symbiotic N-fixation or growth of inherently non-mycorrhizal plant species. Thus, the risks associated with introduced non-pathogenic microorganisms are very low.

Respuesta del simbiosistema frijol (Phaseolus vulgaris L.) y Rhizobium tropici CIAT899 ante el efecto alelopático de Ipomoea purpurea L. Roth / Responses of the common bean (Phaseolus vulgaris L.) and Rhizobium tropici CIAT899 symbiosystem to induced allelopathy by Ipomoea purpurea L. Roth

La alelopatía es un fenómeno que involucra la producción de metabolitos secundarios que influyen en el crecimiento de las plantas, pero este potencial alelopático ha sido poco estudiado en la simbiosis rizobio-leguminosa. Esta investigación tuvo los siguientes objetivos: 1) evaluar el potencial alelopático de lixiviados acuosos de Ipomoea purpurea L. Roth en la germinación de semillas y en el crecimiento radical de plántulas de frijol (Phaseolus vulgaris L.); 2) determinar el efecto de estos lixiviados en el crecimiento in vitro de Rhizobium tropici CIAT899, y 3) evaluar el potencial alelopático de I. purpurea en el crecimiento, la fisiología y la nodulación de frijol en simbiosis con R. tropici. Tanto el lixiviado acuoso de raíz como el de la parte aérea de I. purpurea estimularon la germinación de semillas de frijol y la elongación radical. El crecimiento in vitro de R. tropici fue inhibido al aplicar los 2 tipos de lixiviado. La presencia de I. purpurea tuvo un efecto negativo en el crecimiento y en las respuestas fisiológicas de las plantas de frijol, que fue atenuado cuando las plantas fueron inoculadas con Rhizobium tropici; no obstante, la nodulación asociada a esta bacteria fue afectada en presencia de la planta alelopática. Los resultados indican que la simbiosis de rizobios en las raíces de frijol es un elemento importante en la atenuación de los danos producidos por la planta alelopática I. purpurea.

Allelopathy is a phenomenon that involves the production of secondary metabolites that influence the growth of plants and microorganisms; however, this alellopathic effect has been scarcely studied on the rhizobia-legume symbiosis. The aims of this research were 1) to assess the allelopathic potential of aqueous extracts of Ipomoea purpurea L. Roth on seed germination and root length of common bean seedlings (Phaseolus vulgaris L.), 2) to determine its effects on the in vitro growth of Rhizobium tropici CIAT899, and 3) to evaluate the allelopathic potential of I. purpurea on the growth, nodulation and physiology of common bean plants inoculated with R. tropici. After 48 h, 15% of the aqueous root extract of I. purpurea stimulated seed germination, whereas 4% of the aqueous shoot extracts stimulated such germination. Both the root or shoot extracts stimulated seed germination and e root length. In vitro growth of R. tropici was inhibited as a result of the application of both aqueous extracts. The presence of I. purpurea negatively affected both the growth and physiological responses of common bean plants, and this effect was attenuated after the inoculation of R. tropici; nevertheless, this allelopathic plant affected root nodulation. Our results suggest that the symbiosis of rhizobia and roots of common bean plants is an important element for attenuating the negative effects caused by the allelopathic plant.

Effect of organic and conventional farming practices on soil microbial population

Aim: Microbial community has an integral role in farming, but there is limited understanding of the complex response of microbial populations to organic and conventional farming systems. Therefore, the present study was carried out to study the effect of organic and conventional farming practices on soil microbial population in Haryana. Methodology: Fifty surface soil samples (0-15 cm) were collected from organic and their adjoining conventional farms at 11 districts of Haryana. Soil samples were processed and analyzed for Rhizobium, Azotobacter, Azospirillium and phosphorous solubilizing bacterial (PSB) counts for the two types of farming systems. Results: In comparison to conventional farming system, overall, population of PSB (which was 25.71×104 CFU g-1 soil) increased significantly to 36.91×104 CFU g-1 soil (an increase of 43.5%). Similarily, Rhizobium population in organic farming system increased from 29.26×104 CFU g-1 soil to 42.14×104 CFU g-1 soil (an increase of 44.1%). The population of Azotobacter increased significantly from 15.83×104 to 22.01×104 CFU g-1 soil (39.0%), while Azospirillium population increased from 13.66×104 to 20.10×104 CFU g-1 with an increase of 47.1%. Thus, it is clear from the results that organic nutrient sources showed a stimulating influence on the microbial populations of organic farming. Interpretation: Higher microbial population recorded in organic farming in comparison to conventional farming leads to better soil health and increased productivity.

Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restriction, and AMPylating enzymes

Background: The whole-genome sequences of nine Rhizobium species were evaluated using different in silico molecular techniques such as AFLP-PCR, restriction digest, and AMPylating enzymes. The entire genome sequences were aligned with progressiveMauve and visualized by reconstructing phylogenetic tree using NTSYS pc 2.11X. The "insilico.ehu.es" was used to carry out in silico AFLP-PCR and in silico restriction digest of the selected genomes. Post-translational modification (PTM) and AMPylating enzyme diversity between the proteome of Rhizobium species were determined by novPTMenzy. Results: Slight variations were observed in the phylogeny based on AFLP-PCR and PFGE and the tree based on whole genome. Results clearly demonstrated the presence of PTMs, i.e., AMPylation with the GS-ATasE (GlnE), Hydroxylation, Sulfation with their domain, and Deamidation with their specific domains (AMPylating enzymes) GS-ATasE (GlnE), Fic, and Doc (Phosphorylation); Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase; Sulfotransferase; and CNF (Cytotoxic Necrotizing Factors), respectively. The results pertaining to PTMs are discussed with regard to functional diversities reported in these species. Conclusions: The phylogenetic tree based on AFLP-PCR was slightly different from restriction endonuclease- and PFGE-based trees. Different PTMs were observed in the Rhizobium species, and the most prevailing type of PTM was AMPylation with the domain GS-ATasE (GlnE). Another type of PTM was also observed, i.e., Hydroxylation and Sulfation, with the domains Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase and Sulfotransferase, respectively. The deamidation type of PTM was present only in Rhizobium sp. NGR234. How to cite: Qureshi MA, Pervez MT, Babar ME, et al. Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restrictions and ampylating enzymes.

Inhibitory Effect of Rhizobia Isolated from Several Leguminous against Phytopathogenic Fungi

Aims: This study was carried out to evaluate the antagonistic effect of ten isolated characterized Rhizobium sp. and three referenced strains against aggressive phytopathogenic fungi Fusarium spp., Aspergillus spp., Penicillium spp., Alternaria spp., Humicola spp. and Cladosporium spp. isolated from infected and wilted plants in vitro and in vivo. Study Design:  First, we have ten strains of rhizobia isolated from leguminous and characterized, after that,  some strains of fungi were isolated from infected  and wilt plants,  such as Fusarium, Aspergillus, Penicillium,  Alternaria, Humicola and Cladosporium. Finally, The investigation of the potential of the isolated rhizobia and three referenced strains was evaluated in dual culture, in pots experiments and on seeds. Place and Duration of Study: The study was carried out at the Department of Microbiology, Faculty of Nature and Life Sciences, Laboratory of Applied Microbiology, between April and November 2016. Methodology: Rhizobia isolates were identified upon their phenotypic traits as: the morphology of the colony, of the physiological characters (growth temperature, salt tolerance, resistance to antibiotics, metabolism of carbon source, generation time…) and also the production of extracellular metabolites as siderophores and proteases. Fungal isolates were identified by their macroscopic and microscopic characters. The antagonistic effect of rhizobia against phytopathogenic fungi was examined in vitro by: confrontation in Petri dishes and inoculation of seeds; and in vivo by inoculation of plants. Results: The isolated rhizobia were resistant to penicillin and amoxicillin with generation time ranged from 1.9 to 6.4 h, they were able to grow at temperatures from 4°C to 37°C, tolerate salt concentration (0.5 –2%) and produce siderophores and proteases. The results demonstrated the effectiveness of the rhizobia isolates and the referenced strains against the fungi isolates in vitro and in vivo. In dual culture, all rhizobia isolates inhibited the mycelial growth of the pathogens. The best disease control was obtained with isolate F3 from faba bean which inhibited the fungal growth with more than 70%. The highest inhibition growth was obtained against Alternaria spp.2, Penicillium spp.2, Cladosporium spp. and Humicola spp. with an inhibition rate ranging from 90 to 96%. In pot experiments, Rhizobia isolates from chickpea, lentil and faba bean reduced significantly all disease incidence  with more than 75%; where the best fight was observed in lentil plants, while in faba bean no wilted plants were observed. Seeds inoculated with rhizobia and fungi in Petri dishes showed that isolates from faba bean and lentil were the most effective in reducing fungi disease incidence. Conclusion: Rhizobia have a high potentiality to inhibit the growth of tested pathogens and could be fielded within an integrated disease management package.

In silico analysis of a Rhizobium sp. RC1 putative haloalkanoic permease sequence motif and classification

Aims@#The transport of haloalkanoic acids (haloacids) is important in the metabolism of haloacid pollutants by bacteria. In this study, a computational analysis of Rhizobium sp. RC1 haloacid permease (DehrP) amino acid sequence was conducted to identify its subfamily, sequence motifs and evolutionary position among closely related transporters. @*Conclusion, significance and impact of study@#Blast search in the Pfam and Transmembrane Classification Databases was used to establish the classification and the subfamily of DehrP. Clustal omega sequence alignment approach and MEME Suite motif-based analysis tools were used to locate the transporter motifs of DehrP. Dotplots of DehrP sequence was computed using the EMBOSS Dotmatcher. MEGA7 software was used to analyze the phylogenetic position of DehrP among closely related symporters in the Transmembrane Classification Database. Comparative analysis by Pfam shows that DehrP is a member of the Major Facilitator Superfamily (#2.A.1). PSI-Blast against the Transmembrane Classification Database shows that DehrP is significantly aligned with a subfamily of transporters called the Metabolite: H+ Symporters (#2.A.1.6). DehrP has six similar sequence motifs with the Metabolite: H+ Symporter proteins including the functional motif of GXXXDRXGRR. DehrP is evolutionarily related to Burkholderia caribensis MBA4 Haloacid: H+ Symporters (Dehp2 and Deh4p). @*Methodology and results@#Based on sequence similarity, DehrP is a Major Facilitator Superfamily protein that belongs to the Metabolite: H+ Symporter protein subfamily which might coordinate the transport of a haloacid coupled with a proton (H+). Mutagenesis of DehrP sequence motifs might be useful in the engineering of Rhizobium sp. RC1 for efficient uptake and degradation of haloacids.

Roles of quorum sensing molecules from Rhizobium etli RT1 in bacterial motility and biofilm formation

ABSTRACT Strain RT1 was isolated from root nodules of Lens culinaris (a lentil) and characterized as Rhizobium etli (a Gram-negative soil-borne bacterium) by 16S rDNA sequencing and phylogenetic analysis. The signaling molecules produced by R. etli (RT1) were detected and identified by high-performance liquid chromatography coupled with mass spectrometry. The most abundant and biologically active N-acyl homoserine lactone molecules (3-oxo-C8-HSL and 3-OH-C14-HSL) were detected in the ethyl acetate extract of RT1. The biological role of 3-oxo-C8-HSL was evaluated in RT1. Bacterial motility and biofilm formation were affected or modified on increasing concentrations of 3-oxo-C8-HSL. Results confirmed the existence of cell communication in RT1 mediated by 3-oxo-C8-HSL, and positive correlations were found among quorum sensing, motility and biofilm formation in RT1.

Characterization of rhizobia isolates obtained from nodules of wild genotypes of common bean

Abstract This study aimed to evaluate the tolerance to salinity and temperature, the genetic diversity and the symbiotic efficiency of rhizobia isolates obtained from wild genotypes of common bean cultivated in soil samples from the States of Goiás, Minas Gerais and Paraná. The isolates were subjected to different NaCl concentrations (0%, 1%, 2%, 4% and 6%) at different temperatures (28 °C, 33 °C, 38 °C, 43 °C and 48 °C). Genotypic characterization was performed based on BOX-PCR, REP-PCR markers and 16S rRNA sequencing. An evaluation of symbiotic efficiency was carried out under greenhouse conditions in autoclaved Leonard jars. Among 98 isolates about 45% of them and Rhizobium freirei PRF81 showed a high tolerance to temperature, while 24 isolates and Rhizobium tropici CIAT899 were able to use all of the carbon sources studied. Clustering analysis based on the ability to use carbon sources and on the tolerance to salinity and temperature grouped 49 isolates, R. tropici CIAT899 and R. tropici H12 with a similarity level of 76%. Based on genotypic characterization, 65% of the isolates showed an approximately 66% similarity with R. tropici CIAT899 and R. tropici H12. About 20% of the isolates showed symbiotic efficiency similar to or better than the best Rhizobium reference strain (R. tropici CIAT899). Phylogenetic analysis of the 16S rRNA revealed that two efficient isolates (ALSG5A1 and JPrG6A8) belong to the group of strains used as commercial inoculant for common bean in Brazil and must be assayed in field experiments.

In silico molecular analysis of novel L-specific dehalogenase from Rhizobium sp. RC1

Aims: This study presents the first structural model and proposed the identity of four important key amino acid residues, Asp13, Arg51, Ser131 and Asp207 for the stereospecific haloalkanoic acid dehalogenase from Rhizobium sp. RC1. Methodology and results: The enzyme was built using a homology modeling technique; the structure of crystallized LDEX YL from Pseudomonas sp. strain YL as a template. Model validation was performed using PROCHECK to generate the Ramachandran plot. The results showed 80.4% of its residues were located in the most favoured regions suggested that the model is acceptable. Molecular dynamics simulation of the model protein was performed in water for 10 nanoseconds in which Na+ was added to neutralize the negative charge and achieved energy minimization. The energy value and RMSD fluctuation of Cα backbone of the model were computed and confirmed the stability of the model protein. Conclusion, significance and impact of study: In silico or computationally based function prediction is important to complement with future empirical approaches. L-haloacid dehalogenase (DehL), previously isolated from Rhizobium sp. RC1 was known to degrade halogenated environmental pollutants. However, its structure and functions are still unknown. This structural information of DehL provides insights for future work in the rational design of stereospecific haloalkanoic acid dehalogenases.

Industrial wastewater as raw material for exopolysaccharide production by Rhizobium leguminosarum

The objective of this study was to evaluate the exopolysaccharide (EPS) production by Rhizobium leguminosarum cultivated in wastewater generated by oil companies (WWOC1 and WWOC2) and fish processing industry (WWFP). The results obtained in Erlenmeyer flasks indicated that the rhizobial strain grew well in industrial wastewater. Generally, wastewater composition affected the growth and the EPS production. WWFP allowed good bacterial growth similar to that obtained with the standard medium (YMB). During growth, various quantities of EPS were produced and yields varied depending on the media. Growing in YMB, EPS production did not exceed 9.7 g/L obtained after 72 h of growth. In wastewater, the maximum EPS value reached 11.1 g/L obtained with the fish processing wastewater, after 72 h of growth. The use of a mixture of the oil company wastewater (WWOC2) and the fish processing wastewater (WWFP) as culture medium affected not only the rhizobial strain growth, but also EPS production. The highest EPS (42.4 g/L, after 96 h of culture) was obtained using a ratio of WWFP and WWOC2 of 50:50 (v:v). Therefore, this work shows the ability of Rhizobium leguminosarum, growing in industrial wastewater as new economic medium, to produce EPS. This biopolymer could be applied in enormous biotechnological areas.

Genotypic Variation for Response to Rhizobial Sp. and Piriformospora Indica for Yield and Yield Components in Mungbean [Vigna Radiata (L.) Wilczek].

Ten mungbean genotypes were evaluated to estimate the genotypic variation for seed yield components and Nitrogen and Phosphorus uptake after inoculating with three microbial treatments (Rhizobium, Piriformospora indica and their combined inoculation). Significant genotypic differences for all characters indicated presence of considerable variability. All the microbial treatments and genotype x microbial interaction differed significantly except for maturity, branches/plant and seeds/pod. The traits affected most by Rhizobium inoculation in majority of the genotypes were plant height, pods/plant and seed yield. Above 50 per cent P. indica infection in roots was observed in eight genotypes, however, its effect was observed only in a few genotypes on plant height, P content in shoot, 100-seed weight and seed yield. The effect of combined inoculation was observed on seed yield only. Effect of all the three inoculants was observed in only MH-810 and MH-721. Maximum response of Rhizobium and dual inoculation was observed in MH-421.

Analysis of catheter-related blood infections due to Rhizobium radiation in pediatric patients / 中华急诊医学杂志

Objective To analyze catheter-related bloodstream infections due to Rhizobium radiation (R.radiobacter) in pediatric patients.Methods Clinical data of 1 014 pediatric patients with intravascular catheterization were collected from February 2012 to February 2014,including age,length of time a catheter remained in place,laboratory findings and outcome of R.radiobacter bloodstream infection in order to explore the factors for R.radiobacter infection.Results There were 26 children contracting R.radiobacter bloodstream infection children,and of them,21 were under 2 years old (80.77％),and the length of time for catheter dwelt in vessel longer than 5 days in 20 children (76.92％).There were significant differences in age under 2 years old,length of time longer than 5 days for catheter remained in place,CD4 and CD4/ CD8 between 26 children with R.radiobacter infection and uninfected children (P ＜ 0.01).The re-infection with different varieties of bacterial strains was found in 12 of all R.radiobacter infection children (46.15％) after treatment,and of them,R.radiobacter bloodstream infection was detected twice in 2 children,and 2 died (7.69％).Conclusions Age under 2 years old,the length of time for intra-vascular catheter remained in place longer than 5 days,and weakened immunity are the important risk factors of R.radiobacter bloodstream infection,and the improper medical care may be the cause of re-infections in pediatric patients with prolonged intra-vascular catheter-dwelling.

Evaluation on laboratory diagnosis of catheter-related bloodstream infec-tion due to Rhizobium radiobacter in pediatric patients / 中国感染控制杂志

Objective To evaluate diagnostic method and infection factors for catheter-related bloodstream infec-tion(CRBSI)due to Rhizobium radiobacter (R.radiobacter)in pediatric patients.Methods Clinical data of 1 014 pediatric patients with central venous catheter(CVC)-related treatment in a hospital from February 2012 to February 2014 were collected,semi-quantitative culturing of catheter,colony forming unit (CFU)ratio of catheter to venous blood,difference in culture time between venous blood and catheter were detected among patients with R.radiobact-er infection;factors for R.radiobacter infection were analyzed.Results Of 1 014 pediatric patients who used CVC, 32 were detected R.radiobacter from catheter blood,28 were detected from venous blood,27 were detected from both catheter and venous blood.Catheter semi-quantitative culture of 27 patients were ≥ 15 CFU,5 were5 days are risk factors for R.radiobacter bloodstream infection.

Genotypes and antimicrobial susceptibility of Rhizobium radiobacter isola-ted from pediatric patients with bacteremia / 中国感染控制杂志

Objective To investigate genotypes and antimicrobial susceptibility of Rhizobium radiobacter (R.radiobact-er)isolated from pediatric patients with bacteremia.Methods R.radiobacter strains from blood cultures of pediatric pa-tients with bacteremia from February 2013 through February 2014 were collected.16S rDNA fragment was amplified by polymerase chain reaction(PCR),bacterial genotypes were identified by pulsed-field gel electrophoresis (PFGE),antimi-crobial susceptibility testing were performed by Kirby-Bauer disk diffusion method.Results 13 isolates of R.radiobacter were isolated from 12 children with positive blood culture,which including 3 genotypes,the homology of 16S rDNA fragment and R.radiobacter IFM 10623 was up to 99%.According to CLSI 2003 standard,these 13 R.radiobacter were resistant to ceftazidime,piperacillin,ticarcillin,piperacillin/tazobactam,ticarcillin/clavulanic acid,aztreo-nam and polymyxin B,but sensitive to cefepime,doripenem,imipenem,meropenem,tobramycin,netilmicin,cip-rofloxacin,levofloxacin,and norfloxacin.In addition,cefotaxime and ceftriaxone showed larger inhibition zone. Conclusion Therapy of R.radiobacter infection should be based on antimicrobial susceptibility testing results;cefo-taxime and ceftriaxone are better selection for the therapy of R.radiobacter infection in pediatric patients.

Infectividad y efectividad de rizobios aislados de suelos de la Costa Caribe colombiana en Vigna unguiculata / Infectivity and effectiveness of isolated rhizobia from colombian Caribbean Soils in Vigna unguiculata

Es el primer estudio en Colombia que abarca una evaluación de rizobios nativos asociados a frijol Caupí (Vigna unguiculata L. Walp.) en los departamentos del Cesar y la Guajira. En esta investigación, se demostró que la utilización de aislamientos de rizobios nativos aislados a partir de nódulos, mejoraron el desarrollo del frijol Caupí (Vigna unguiculata L. Walp.), siendo estas bacterias más eficientes que los tratamientos químicos y absolutos (sin inóculo ni fertilización) y que las cepas inducidas mejorando además, la fijación biológica de nitrógeno y la tasa fotosintética. Como aportes del estudio, se determinó que en condiciones de invernadero la fertilización biológica fue más eficiente que la química y que, de acuerdo a los resultados obtenidos de las diferentes variables agronómicas evaluadas, esto podría influir positivamente en los rendimientos nutricionales del cultivo, base alimentaria de los sistemas ganaderos de estas regiones del país y fuente alimenticia de la comunidad indígena y de bajos recursos económicos.

This is the first study in Colombia which covers an evaluation of native rhizobium associated to the Caupí bean (Vigna unguiculata L. Walp.) in the departaments of Cesar and Guajira. In this research it was demonstrated that the use of native rhizobium isolated from nodes, improved the development of the Caupí bean (Vigna unguiculata L. Walp.), being this bacteria more efficient than the chemical and absolute treatments (without inoculum and fertilization) also improving the biological nitrogen fixation and the photosynthetic rate. As contribution of the study, it was determined that in greenhouse conditions and according to the results obtained from differents measured agronomic variables, this could influence positively in the nutritional performance of the crop, basis of food of the cattle system of this regions of the country and the food source of the indigenous community of low economic income.

Effect of Different Carbon and Nitrogen Sources on Growth and Indole Acetic Acid Production by Rhizobium Species Isolated from Cluster Bean [Cyamopsis tetragonoloba (L.)].

Five Rhizobium strains (Cb1, Cb2, Cb3, Cb4 and Cb5) were isolated from root nodules of cluster bean [Cyamopsis tetragonoloba (L.)] on yeast extract mannitol agar (YMA) medium. All the five Rhizobium isolates have shown the Indole Acetic Acid( IAA) production in culture medium supplemented with L-tryptophan. The IAA content in culture supernatant was estimated by using the colorimetric method (13). All the five Rhizobium isolates produced maximum amount of IAA in medium supplemented with 2.5mg/ml Ltryptophan concentration. Production of IAA was maximum at 72h of incubation when bacteria reached the stationary phase. The cultural conditions were optimized for maximum IAA production by using different carbon and nitrogen sources as well as changing the incubation period. Glucose and L-asparagine were found to be the best carbon and nitrogen sources, respectively for maximum IAA production. The cell wall affecting agent, penicillin increased the IAA production up to 77.95% in Cb4, 59.52% in Cb5 and 37.84% in Cb3 isolates, over the control. Among the five isolates studied, isolate Cb4 showed better performance in IAA production.

Screening of Rhizobium Strains Isolated from the Root Nodules of Vigna mungo Cultivated in Rice Fallows for Their Phosphate Solubilizing Ability and Enzymatic Activities.

Aims: The present work is aimed to find out the enzymatic activities and phosphate solubilizing efficiency of indigenous rhizobia confined to rice fallows. Study Design: In this experiment we maintained random block design (RBD). Place and Duration of Study: This work was carried out in the Department of Botany and Microbiology, Acharya Nagarjuna University between October 2012 and December 2013. Methodology: In this study, we have isolated 19 Rhizobium strains collected from the healthy root nodules of Vigna mungo cultivated in rice fallows on yeast extract mannitol agar (YEMA) medium. The strains were confirmed as Rhizobia by using Gram staining, growth on YEMA with congo red, growth in Hofer’s alkaline broth, growth on glucose peptone agar, acid production, ketolactose test and nodulating ability was tested on homologous hosts by plant infection tests. Phosphate solubilization ability of the isolated Rhizobium strains were carried out Pikovskaya’s agar medium. Results: Eight out of 19 strains tested for phosphate solubilizing ability on Pikovskaya’s agar medium containing tri calcium phosphate (TCP) as insoluble phosphate source showed zone of TCP solubilization. The strain VM-2 exhibited maximum solubilization after 48h of incubation, while least activity was found with VM-11. Effect of different carbon and nitrogen sources on phosphate solubilizing ability of Rhizobial strains was tested and maximum phosphate solubilization (799μg/ml) by VM-2 was observed when glucose and ammonium sulphate were used as carbon and nitrogen sources. Conclusion: In this study it is concluded that along with symbiotic nitrogen fixtation, some Rhizobium species were found to be involved in phosphate solubilization and this ability of phosphate solubilization by the Rhizobium strains can be exploited as PGPR.

Crescimento de cultivares de arroz (Oryza sativa L. ) influenciado pela inoculação com bactérias promotoras de crescimento de plantas / Growth of rice cultivars (Oryza sativa L. ) as affected by inoculation with plant growth-promoting bacteria

Este trabalho objetivou avaliar o efeito da inoculação de seis estirpes de bactérias promotoras de crescimento de plantas (BPCP), Burkholderia spp. (B7 e B16), Pseudomonas spp. (P18 e P21) e Rhizobium spp. (R65 e R82) e duas misturas contendo uma estirpe de cada gênero no crescimento de seis cultivares de arroz (BRS Bonança, BRS Aimoré, BRS Talento, BRSMG Curinga, Japonês e Bolinha). As características fisiológicas das bactérias foram determinadas em ensaios in vitro. Foi conduzido um experimento sob condições de casa de vegetação onde as BPCP foram inoculadas em cultivares de arroz, cultivados em vasos contendo 1 kg de solo, em delineamento de blocos casualizados com 4 repetições. Aos 60 dias após a emergência foram avaliados parâmetros de crescimentos relacionados à parte aérea e ao sistema radicular dos cultivares de arroz. Entre as bactérias, somente duas (B7 e R65) não apresentaram capacidade de produção in vitro de auxina. Todas as estirpes apresentaram atividade de catalase e formação de película em meio NFb semi-sólido sem N ou presença de nódulo em feijoeiro, indicando capacidade de fixação biológica de nitrogênio. A inoculação das BPCP em arroz proporcionou aumentos médios de 10% em relação ao controle para a área foliar e massa seca da parte aérea e de 9% para o comprimento e massa seca de raiz. Entre os cultivares, BRS Aimoré apresentou maior interação com as estirpes estudadas e a estirpe P21 de Pseudomonas spp. proporcionou diferença significativa em relação ao controle em parâmetros relacionados à parte aérea e ao sistema radicular.

Aiming to evaluate the effect of the inoculation of six strains of plant growth-promoting bacteria (PGPBs) Burkholderia spp. (B7 and B16), Pseudomonas spp. (P18 and P21) and Rhizobium spp. (R65 and R82) and two mixtures containing one strain of each genera on the growth of six rice cultivars (BRS Bonança, BRS Aimoré, BRS Talento, BRSMG Curinga, Japonês and Bolinha). Physiological characteristics of the bacteria were determined on in vitro assays. Rice cultivars were inoculated with PGPB under greenhouse conditions and cultivated on 1 kg pots filled with soil on a randomized block design with four replicates. At 60 days after emergence growth parameters related with the shoot and root were evaluated for rice cultivars. Among the evaluated bacteria only two (B7 and R65) were not able to produce auxin under in vitro conditions. All strains showed catalase activity and film formation in semisolid medium NFb without N or nodulation in common bean, indicating the ability of biological nitrogen fixation. Inoculation of PGPBs in rice provided increases of 10% as compared to the control regarding leaf area and dry mass of shoots and 9% for length and root dry weight. Among the cultivars BRS Aimoré showed greater interaction with the strains studied and the strain P21 of Pseudomonas spp. promoted significant difference compared to the control for the parameters related with the shoot and root system.