Población de cianobacterias en suelos arroceros: efecto de las rotaciones / Cyanobacteria populations in rice soils: rotation effects

Este trabajo tuvo como objetivo evaluar el efecto de rotaciones arroceras sobre la población de cianobacterias durante el ciclo de cultivo. El estudio se condujo en Entre Ríos (Argentina). Se evaluaron cuatro rotaciones: arroz-soja (AS); arroz-soja-maíz-soja (ASMS): arroz-arroz (AA) y arroz-pradera (AP). Muestras de suelo y agua se tomaron en cuatro estados del cultivo: implantación, macollaje, panoja embuchada y madurez fisiológica. El número potencial de cianobacterias fue menor en relación a otras áreas arroceras. Los menores recuentos se registraron en el período de implantación y los mayores en el de panoja embuchada. El análisis estadístico no mostró efecto de las rotaciones sobre el número de cianobacterias, aunque AA presentó la mayor abundancia. Se reconocieron un total de 13 géneros de cianobacterias Lyngbya, Oscillatoria,Plectonema, Spirulina, Anabaena, Nostoc, Aulosira, Calothrix, Gloeotri-chia, Aphanocapsa,Croococcus, Mycrocystis y Gloeocapsa. La rotación AP registró la riqueza de géneros.Las rotaciones AS y AA presentaron mayor proporción de cianobacterias filamentosas. Los valores de biodiversidad de Simpson fueron bajos. Se concluyó que las rotaciones arroceras evaluadas tuvieron efecto sobre la proporción de cianobacterias unicelulares a filamentosas, los géneros presentes y la riqueza.

The aim of this study was to evaluate the effect of different rice rotations on cyanobacteria populations during the growing season. The study was conducted in Entre Ríos (Argentina). Four crop rotations were evaluated: rice-soybean (AS); rice-soybean-corn-soybean (ASMS); rice-rice (AA) and rice-pasture (AP). Soil and water samples were collected in 4 stages: implantation, tillering, booting and physiological maturity. The potential number of cyanobacteria population was lowerin relation to other rice sites previously reported. The lowest counts were recorded during implantation whereas the highest counts were obtained during booting. The statistical analysis showed no effect of rotation on the variable number of cyanobacteria, although AA was the most abundant. A total of 13 taxa were identified: Lyngbya, Oscillatoria, Plectonema, Spirulina, Anabaena, Nostoc, Aulosira, Calothrix, Gloeotrichia, Aphanocapsa, Croococcus, Mycrocystis and Gloeocapsa. AP rotation recorded the lowest number of genera. AS and AA had a higher proportion of filamentous cyanobacteria. Simpson's index was low. It was concluded that crop rotations had a differential effect on some aspects of cyanobacteria population such as the proportion of unicellular to filamentous cyanobacteria, genera presence and richness.

Aislamiento de Bacillus cereus en restaurantes escolares de Colombia / Isolation of Bacillus cereus in school restaurants in Colombia

Resumen Introducción. Bacillus cereus es reconocido como un agente patógeno causante de intoxicaciones alimentarias. Se trata de una bacteria de metabolismo aerobio facultativo capaz de formar esporas, lo que le permite sobrevivir a la pasteurización y el calentamiento e, incluso, a la irradiación con los rayos gamma usados para reducir los agentes patógenos de los alimentos. Objetivo. Estudiar la presencia de B. cereus y su toxina diarreica en el arroz y en alimentos a base de cereales, harinas o féculas listos para el consumo en restaurantes escolares de algunos departamentos de Colombia. Materiales y métodos. Se hizo un estudio descriptivo y transversal con alimentos listos para el consumo distribuidos en restaurantes escolares de los departamentos que más notifican enfermedades transmitidas por alimentos al sistema de vigilancia, así como en los de menor notificación. Resultados. Se recolectaron 479 muestras en ocho departamentos, 74 municipios y 363 restaurantes escolares; el 63 % correspondió a muestras de arroz y el 37 % a alimentos como coladas. El 9 % de las muestras analizadas fueron positivas para B. cereus y, en el 91 % de estas, se detectó la toxina diarreica. Conclusiones. En todos los departamentos estudiados se encontró B. cereus. El manejo de materias primas y el inadecuado tratamiento térmico de los alimentos fueron los factores directamente relacionados con las enfermedades transmitidas por alimentos. Es importante reforzar la vigilancia e incentivar la investigación y la notificación de los brotes de enfermedades transmitidas por alimentos para mejorar la calidad de la información, llevar a cabo acciones de comunicación, prevención y coordinación intersectorial, y con los manipuladores, con el fin de adoptar las medidas necesarias que garanticen la inocuidad de los alimentos, así como la eliminación de los factores de riesgo de estas enfermedades.

Abstract Introduction: Bacillus cereus is recognized as a pathogen that causes food poisoning. It is a facultative aerobic metabolism bacterium capable of forming spores, which allows it to survive pasteurization and heating even by the gamma irradiation used to reduce pathogens in food. Objective: To study the presence of Bacillus cereus and its diarrheal toxin in rice and ready-to-eat cereals, flours, and starches in school restaurants in Colombia. Materials and methods: We conducted a descriptive cross-sectional study of ready-to-eat foods distributed in school restaurants in the departments with the most and the least notification of foodborne diseases to the surveillance system. Results: A total of 479 samples were collected from eight departments, 74 municipalities, and 363 school restaurants, 63% of which were rice samples and 37%, starchy food samples; 9% of them tested positive for Bacillus cereus. In 91% of the samples that tested positive, the bacterium was isolated with the presence of the diarrheal toxin. Conclusions: In all the departments with B. cereus in the samples, the factors directly related to food-borne diseases were the handling of raw materials and the poor thermal treatment of food. Strengthening surveillance by stimulating research and reporting on outbreaks of foodborne diseases is important to improve the quality of information, to develop communication, prevention and intersectional coordination and manipulation measures, as well as to take the necessary actions to guarantee the safety of food and to eliminate the risk factors that may contribute to this problem.

Contribution of dark septate fungi to the nutrient uptake and growth of rice plants

ABSTRACT The use of dark septate fungi (DSE) to promote plant growth can be beneficial to agriculture, and these organisms are important allies in the search for sustainable agriculture practices. This study investigates the contribution of dark septate fungi to the absorption of nutrients by rice plants and their ensuing growth. Four dark septate fungi isolates that were identified by Internal transcribed spacer phylogeny were inoculated in rice seeds (Cv. Piauí). The resulting root colonization was estimated and the kinetic parameters Vmax and Km were calculated from the nitrate contents of the nutrient solution. The macronutrient levels in the shoots, and the NO3--N, NH4+-N, free amino-N and soluble sugars in the roots, sheathes and leaves were measured. The rice roots were significantly colonized by all of the fungi, but in particular, isolate A103 increased the fresh and dry biomass of the shoots and the number of tillers per plant, amino-N, and soluble sugars as well as the N, P, K, Mg and S contents in comparison with the control treatment. When inoculated with isolates A103 and A101, the plants presented lower Km values, indicating affinity increases for NO3--N absorption. Therefore, the A103 Pleosporales fungus presented the highest potential for the promotion of rice plant growth, increasing the tillering and nutrients uptake, especially N (due to an enhanced affinity for N uptake) and P.

Polyphasic characterization of bacteria obtained from upland rice cultivated in Cerrado soil

ABSTRACT This work aimed to characterize 20 isolates obtained from upland rice plants, based on phenotypic (morphology, enzymatic activity, inorganic phosphate solubilization, carbon source use, antagonism), genotypic assays (16S rRNA sequencing) and plant growth promotion. Results showed a great morphological, metabolic and genetic variability among bacterial isolates. All isolates showed positive activity for catalase and protease enzymes and, 90% of the isolates showed positive activity for amylase, catalase and, nitrogenase. All isolates were able to metabolize sucrose and malic acid in contrast with mannitol, which was metabolized only by one isolate. For the other carbon sources, we observed a great variability in its use by the isolates. Most isolates showed antibiosis against Rhizoctonia solani (75%) and Sclerotinia sclerotiorum (55%) and, 50% of them showed antibiosis against both pathogens. Six isolates showed simultaneous ability of antibiosis, inorganic phosphate solubilization and protease activity. Based on phylogenetic analysis of the 16S rRNA gene all the isolates belong to Bacillus genus. Under greenhouse conditions, two isolates (S4 and S22) improved to about 24%, 25%, 30% and 31% the Total N, leaf area, shoot dry weight and root dry weight, respectively, of rice plants, indicating that they should be tested for this ability under field conditions.

Dark septate endophyte decreases stress on rice plants

Abstract Abiotic stress is one of the major limiting factors for plant development and productivity, which makes it important to identify microorganisms capable of increasing plant tolerance to stress. Dark septate endophytes can be symbionts of plants. In the present study, we evaluated the ability of dark septate endophytes isolates to reduce the effects of water stress in the rice varieties Nipponbare and Piauí. The experiments were performed under gnotobiotic conditions, and the water stress was induced with PEG. Four dark septate endophytes were isolated from the roots of wild rice (Oryza glumaepatula) collected from the Brazilian Amazon. Plant height as well as shoot and root fresh and dry matter were measured. Leaf protein concentrations and antioxidant enzyme activity were also estimated. The dark septate endophytes were grown in vitro in Petri dishes containing culture medium; they exhibited different levels of tolerance to salinity and water stress. The two rice varieties tested responded differently to inoculation with dark septate endophytes. Endophytes promoted rice plant growth both in the presence and in the absence of a water deficit. Decreased oxidative stress in plants in response to inoculation was observed in nearly all inoculated treatments, as indicated by the decrease in antioxidant enzyme activity. Dark septate endophytes fungi were shown to increase the tolerance of rice plants to stress caused by water deficiency.

Sensibilidad in vitro de Trichoconiella padwickii a diversos principios activos usados como fungicidas en el cultivo del arroz / In vitro susceptibility of Trichoconiella padwickii to various active ingredients used as fungicides in the cultivation of rice

El objetivo de este trabajo fue evaluar in vitro la sensibilidad micelial de Trichoconiella padwickii a diferentes principios activos por medio del cálculo de la concentración inhibitoria media (CI50). Para ello se realizaron siembras de discos de inóculo en agar poroto con distintas concentraciones (0,1; 1; 10; 30, 50; 100 y 1.000 mg/l) de diversos fungicidas. A los 7 días se midió el diámetro de crecimiento de la colonia (cm). Los datos obtenidos se ajustaron a modelos de regresión no lineal. La sensibilidad se clasificó utilizando la escala de Edgington. Los resultados obtenidos demuestran que el patógeno es muy sensible a los productos que actúan sobre la cadena respiratoria (quinone outside inhibitors QoI y succinate dehydrogenase inhibitors SDHI) y la membrana celular (multisitio), y moderadamente sensible a los que interfieren en la división celular (metil benzimidazol carbamatos MBC), en la síntesis de ácidos nucleicos (fenilamidas PA) y en la transducción de la señal osmótica (actividad multisitio). Este trabajo es el primer antecedente sobre la sensibilidad in vitro de T. padwickii a principios activos fungicidas.

The aim of this study was to evaluate in vitro the mycelial susceptibility of Trichoconiella padwickii to different active ingredients through average median concentration IC50 calculation. Inoculum disks were seeded on bean agar at different concentrations (0.1; 1; 10; 30, 50; 100 and 1000 mg/l) of various fungicides. After seven days the colony diameter was measured. The data obtained were fitted to nonlinear regression models. Susceptibility was classified using the scale proposed by Edgington. The results show that the pathogen is very sensitive to products that act on the respiratory chain (quinone outside inhibitors QoI and succinate dehydrogenase inhibitors SDHI) and cell membrane (multi-site contact activity), and moderately sensitive to those products interfering with cell division (methyl benzimidazole carbamates MBC), synthesis of nucleic acids (phenylamides PA) and osmotic signal transduction (multi-site contact activity). This work is the first record on the sensitivity of T. padwickii.

Fermentação em estado sólido de Aspergillus parasiticus e produção de aflatoxinas / Solid state fermentation of Aspergillus parasiticus and aflatoxin production

Aflatoxinas são metabólitos secundários de fungos com grande potencial carcinogênico, produzidos principalmente por Apergillus flavus e Aspergillus parasiticus. Em vista da ampla variedade de alimentos em que se encontram essas micotoxinas, o presente estudo teve como objetivo determinar condições de cultivo para o Aspergillus parasiticus e produção das quatro principais aflatoxinas (AFB1, AFB2, AFG1 e AFG2) considerando diferentes substratos conhecidos pela contaminação por estas micotoxinas, entre eles arroz branco, arroz cateto, amendoim, milho e farinha de trigo integral, e diferentes valores de umidade e pH. Ao analisar por cromatrografia em camada delgada os extratos dos diferentes substratos, verificou-se a produção de aflatoxinas em todos os alimentos, porém na cromatografia líquida de alta eficiência foi possível perceber a maior produção de aflatoxinas no arroz cateto e na farinha de trigo integral. Para a continuidade do trabalho, utilizou-se o arroz cateto e então preparou- se diferentes meios sólidos com valores de pH entre 3,5 e 7,5 e umidade entre 42 % e 62 %. Ao analisar por CLAE, todas as amostras apresentaram produção de AF, porém as amostras com o maior valor de água agregada (62%) apresentaram maior produção enquanto a variação de pH não apresentou influência nesta produção.

Aflatoxins are secondary metabolites of fungi with great carcinogenic potencial, mainly produced by Aspergillus flavus and Aspergillus parasiticus. In order of the wide variety of foods where mycotoxins are found in, this study aimed to determine growth conditions for Aspergillus parasiticus and production of four major aflatoxins (AFB1, AFB2, AFG1 and AFG2) considering different substrates known for contamination by these aflatoxins, including white rice, cathetus rice, peanuts, maize and whole wheat flour, and different pH and humidity values. When extracts of different substrates were analyzed by thin layer chromatography, it has been verified the production of aflatoxins in all foods; however, when high performance liquid chromatography (HPLC) analysis was performed, the greater production of aflatoxins was observed in cathetus rice and whole-wheat flour. Cathetus rice was then selected to continue the study and different solid medium with pH values between 3.5 and 7.5 and humidity percentages between 42 % and 62 % were prepared. When analyzed by HPLC, all samples showed production of aflatoxins, but the samples with higher humidity value (62%) showed greatest production while the pH changes had no effect on this production.

The morphology and bioactivity of the rice field cyanobacterium Leptolyngbya / Morfología y bioactividad de la cianobacteria Leptolyngbya en los campos de cultivo de arroz

The genus Leptolyngbya comprises filamentous cyanobacteria that are important in rice fields. In the rhizosphere, cyanobacteria produce a variety of secondary metabolites such as auxins that are important in agriculture soil performance. To assess this, Leptolyngbya strain MMG-1, was isolated from the rhizosphere of rice plants and described. For this, the morphology of this strain was studied by light microscopy as well as by confocal laser scanning microscopy. Besides, the ability of this strain to synthesize an auxin-like bioactive compound was demonstrated under various culture conditions (different amounts of tryptophan; pH; different alternating light:dark periods; duration of the incubation). The auxin-like compound was extracted from the culture of Leptolyngbya strain MMG-1 and identified as indole-3-acetic acid (IAA) by thin layer chromatography (TLC) as well as by high performance liquid chromatography (HPLC). Our results showed that the strain required the precursor L-tryptophan for the synthesis of IAA. Leptolyngbya strain MMG-1 accumulated IAA intracellularly. The IAA secreted by Leptolyngbya strain MMG-1 was significantly correlated with the initial concentration of L-tryptophan in the medium, as well as with the duration of the incubation. The bioactivity of the secreted IAA was determined by its effect on the rooting pattern of Pisum sativum seedlings. The culture supernatant of Leptolyngbya strain MMG-1 stimulated the seedling lateral rooting, while it decreased root length. Hence, rhizospheric Leptolyngbya produced auxin under different conditions and affected the plants rooting pattern. Rev. Biol. Trop. 62 (3): 1251-1260. Epub 2014 September 01.

El género Leptolyngbya comprende cianobacterias filamentosas que son importantes en los campos de cultivo de arroz. En la rizosfera, las cianobacterias producen una variedad de metabolitos secundarios, tales como auxinas, que son importantes en el rendimiento de la agricultura del suelo. La cepa Leptolyngbya MMG-1, fue aislada de la rizosfera de plantas de arroz y se describe en este trabajo. La morfología de esta cepa se estudió por microscopía de luz, así como por microscopía confocal de barrido láser. Además, se estimó la capacidad de esta cepa para sintetizar el compuesto bioactivo auxina como se demostró en diversas condiciones de cultivo (diferentes cantidades de triptófano; pH; diferente luz alterna: períodos oscuros; duración de la incubación). La auxina se extrajo a partir del cultivo de la cepa Leptolyngbya MMG-1 y se identificó como ácido indol-3-acético (AA) por cromatografía de capa fina (TLC), así como por cromatografía líquida de alta resolución (HPLC). Nuestros resultados mostraron que la cepa requiere el precursor de L-triptófano para la síntesis de IAA. La cepa Leptolyngbya MMG-1 acumula intracelularmente IAA. El IAA secretada por la cepa Leptolyngbya MMG-1 se correlacionó significativamente con la concentración inicial de L-triptófano en el medio, así como con la duración de la incubación. La bioactividad de la IAA secretada se determinó por su efecto sobre el patrón de enraizamiento de plantas de semillero de Pisum sativum. El sobrenadante del cultivo de la cepa Leptolyngbya MMG-1 estimuló el enraizamiento lateral en la plántula, mientras que se redujo la longitud de la raíz. Por lo tanto, la producción de auxina por Leptolyngbya rizosférica afectó el crecimiento de las plantas.

Diazotrophic bacteria isolated from wild rice Oryza glumaepatula (Poaceae) in the Brazilian Amazon / Bacterias diazotróficas aisladas de arroz silvestre Oryza glumaepatula (Poaceae) en la Amazonia brasileña

The association of wild grasses with diazotrophic bacteria in Brazilian biomes is poorly understood. The isolation and characterization of bacteria associated with wild grasses can contribute to understand the diazotrophic ecology as well as to identify bacteria with biotechnological applications. In this study, we isolated and characterized diazotrophic bacterial isolates from Oryza glumaepatula collected in Cerrado and Forest areas of the Amazon in Roraima State, Brazil. Healthy O. glumepatula plants were collected at five sampling sites at Forest and seven at Cerrado, respectively. The plants were collected at the Cerrado areas in September 2008 while the Forest plants were collected in June/2008 and April/2009. The plants and the soil adhering to the roots were transferred to pots and grown for 35 days in greenhouse conditions. During the harvest, the shoots and the roots were crushed separately in a saline solution; the suspension was diluted serially and inoculated in Petri dishes containing Dyg’s medium. All distinct bacterial colonies were purified in the same medium. The diazotrophic capacity of each bacterium in microaerophilic conditions was assessed in semisolid BMGM medium. In addition, the pellicles forming bacterial isolates were also evaluated by PCR amplification for nifH gene. The diversity of nifH+ bacteria was analyzed by Box-PCR fingerprinting. For selected strains, the growth promoting capacity of O. sativa as a model plant was also evaluated. A total of 992 bacterial isolates were obtained. Fifty- one bacteria were able to form pellicles in the semisolid medium and 38 also positively amplified the 360bp nifH gene fragment. Among the 38 nifH+ isolates, 24 were obtained from the shoots, while 14 originated from the roots. The Box-PCR profiles showed that the bacterial isolates obtained in this study presented a low similarity with the reference strains belonging to the Herbaspirillum, Azospirillum and Burkholderia genus. The growth- promoting ability was confirmed for at least five isolates. For these bacteria, the root and shoot growing results showed higher increases when compared to those observed in plants inoculated with the evaluated reference strains. These results indicate that O. glumaepatula is colonized by a high diverse diazotrophic community in the Brazilian Amazon. Further investigations are now being carried out to determine the taxonomic positions of these isolates and their growth promoting mechanisms.

La asociación de gramíneas silvestres con bacterias diazotróficas en los biomas brasileños es poco conocida. El aislamiento y caracterización de las bacterias asociadas con gramíneas silvestres puede contribuir a entender la ecología de las diazotróficas y bacterias con aplicaciones biotecnológicas. En este estudio, caracterizamos aislamientos bacterianos de diazotróficas de Oryza glumaepatula recolectadas en Cerrado y zonas boscosas de la Amazonía en el estado de Roraima, Brasil. Plantas sanas de O. glumepatula fueron recolectadas en cinco zonas boscosas y siete en Cerrado. Las plantas de Cerrado fueron recolectadas en septiembre 2008, mientras que las del bosque en Junio 2008 y Abril 2009. Las plantas y el suelo adherido a las raíces se transfirieron a macetas y se cultivaron durante 35 días en condiciones de invernadero. Durante la cosecha, los brotes y las raíces se trituraron por separado en una solución salina, la suspensión se diluyó en serie y se inocularon en placas Petri que contenían medio Dyg. Todas las colonias de bacterias se purificaron en el mismo medio. Se evaluó la capacidad diazotrófica de cada bacteria en condiciones microaerofílicas en medio semisólido BMGM. Además, los aislamientos bacterianos que formaron películas se evaluaron también mediante amplificación por PCR para el gen nifH. La diversidad de bacterias nifH+ se analizó por Huella Genética utilizando la Reacción en Cadena de la Polimerasa. Para las cepas seleccionadas, la capacidad de promover el crecimiento de O. sativa como modelo de planta también se evaluó. Se obtuvo un total de 992 cepas bacterianas. Cincuenta y un bacterias fueron capaces de formar películas en el medio semisólido y 38 amplificaron positivamente el fragmento 360bp del gen nifH. De los 38 aislamientos de nifH+, 24 fueron obtenidos de los brotes, mientras que 14 se originaron a partir de las raíces. Los perfiles de PCR-Box mostraron que los aislamientos bacterianos obtenidos en este estudio presentaron una baja similitud con las cepas de referencia pertenecientes a Herbaspirillum, Azospirillum y el género Burkholderia. La capacidad promotora del crecimiento fue confirmada por al menos cinco aislamientos. Para esta bacteria, la raíz y brote mostraron resultados de crecimiento mayores en comparación con los observados en las plantas inoculadas con las cepas de referencia. Estos resultados indican que O. glumaepatula es colonizada por una muy diversa comunidad diazotrófica en la Amazonia brasileña. Se están llevando a cabo otras investigaciones para esclarecer la taxonomía de estas cepas y sus mecanismos para promover el crecimiento.

Toxigenic potential of Fusarium graminearum isolated from maize of northwest Argentina

Twenty six isolates of Fusarium graminearum from grains of maize hybrids harvested in ±west Argentina were grown on autoclaved rice grain to assess their ability to produce type B trichothecenes. Chemical analysis indicated that 38% of isolates were nivalenol (NIV) producers only, 31% were major NIV producers with high DON(deoxynivalenol)/NIV ratios, 8% were major DON producers with minor NIV production, and 23% were DON producers only. Isolates showed a high variability in their toxigenic potential which was not related to fungal biomass. The distribution of the different chemotypes as well as the high and the low trichothecene-producing Fusarium isolates could not be associated to a geographical origin. Our results confirmed for the first time that isolates of Fusarium graminearum from maize of northwest Argentina are able to produce DON and NIV. A substancial contamination with both NIV and DON is likely in maize from northwest Argentina. Their contents should be quantified in regional surveillances for mycotoxin contamination.

Calidad bacteriológica y detección de Bacillus cereus toxigénicos en arroz blanco cocido expendido en el área metropolitana de la provincia de San José, Costa Rica

El gran consumo de arroz a nivel mundial es uno de los factores que favorece su implicación en brotes de origen alimentario y de uno de los patógenos más importantes ligado a este producto como el Bacillus cereus El objetivo del presente trabajo fue evaluar la calidad microbiológica de 50 muestras de arroz blanco cocido expendido en restaurantes de área Metropolitana de San José Costa Rica, incluyendo la determinación del recuento total aerobio mesófilo, Número Más Probable de coliformes totales, fecales y E. coli, B. cereus así como de detección de sus genes nheA, nheB, y nheC. Para el análisis bacteriológico se siguieron los procedimientos descritos en el Compendio de Métodos para el Examen Microbiológico de Alimentos y para la detección de los genes se utililzó un PCR múltiplex y la metodología descrita por Hansen et al., 2001. De las muestras analizadas 46% fueron positivas por coliformes totales, 34% por coliformes fecales, 16% por E. coli, 10% por B. cereus y un 8% por B. cereus toxigénico Lo anterior sugiere que el consumo de arroz blanco en restaurantes puede representar un riesgo para la salud pública y que es necesario implementar mejoras con el fin de brindarle al consumidor un producto inocuo y de mejor calidad.

Bacteriological quality and toxigenic Bacillus cereus detection in cooked white rice sold at the Metropolitan Area of San José, Costa Rica.. The wide use of rice is one of the factors that favors its implication in food borne diseases, and one of the most important pathogens associated to it is Bacillus cereus. The aim of this work was to evaluate the microbiological quality of 50 samples of white cooked rice sold in restaurants at the Metropolitan Area of San José, Costa Rica, including the determination of the total aerobic plate count, the Most Probable Number of total and fecal coliforms and Escherichia coli. MPN of Bacillus cereus and the detection of nheA, nheB and nHeC genes, associated to its toxicity, was also performed. Procedures described in the Compendium of Methods for the Microbiological Examination of Foods were followed for the bacteriological analysis, multiplex PCR was used for the detection of genes following the methodology described by Hansen et al, 2001. 46% of the samples analysed were positive for total coliforms, 34% for fecal coliforms, 16% for E. coli and 10% for B. cereus, being 8% toxigenic. These facts suggest that white cooked rice may represent a risk for Pubic Health and that improvements shall be performed in order to offer a safe and high quality product to consumers.

Aflatoxin contamination in stored rice variety PAU 201 collected from Punjab, India.

Background & objectives: The present study was carried out on stored rice variety PAU 201 in Punjab that was not permitted for milling and public distribution due to the presence of damaged grains at levels exceeding the regulatory limits of 4.75 per cent. The aim of the study was to determine fungal and aflatoxin contamination in the rice samples to assess hazard from the presence of damaged grains. Presence of iron in discoloured rice grains was also assessed. Methods: Stored samples of paddy of PAU 201 rice variety were collected from six districts of Punjab, milled and analysed for presence of fungal and aflatoxin contamination. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and Prussian blue staining was used to determine fungal spores and presence of iron, respectively. Results: Aflatoxin analysis of rice samples indicated that none exceeded the Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011 tolerance limit of 30 μg/kg and majority of the samples had levels <15 μg/kg. The proportion of damaged grains exceeding the limit of 5 per cent was observed in 85.7 per cent of the samples. SEM and Prussian blue staining and EDX analysis of black tipped and pin point damaged rice grains did not show presence of fungal structures and presence of iron. Interpretation & conclusions: The results of the study indicated that the stored rice samples did not pose any health concern with respect to aflatoxin contamination as per the criteria laid down by the Food Safety and Standards Authority of India.

Concentración mínima inhibitoria de higromicina B en callos embriogénicos de arroz -Oryza sativa L / Minimum inhibitory concentration of higromycin B in rice embryogenic calli -Oryza sativa L

Uno de los elementos imprescindibles en la ingeniería genética de plantas es un sistema de selección eficiente. El propósito de este trabajo fue evaluar la sensibilidad al marcador de selección higromicina B, de callos embriogénicos obtenidos a partir del escutelo de semilla de tres variedades colombianas de arroz (FEDEARROZ 2000, FEDEARROZ 50 y FEDEARROZ 369). Además, se validó la respuesta de estas variedades al protocolo de regeneración empleado. Se probaron cuatro concentraciones del antibiótico (25 mg/L, 50 mg/L, 75 mg/L y 100 mg/L) más un control sin higromicina B. Los resultados obtenidos mostraron que una concentración de 50 mg/L de antibiótico en el medio de regeneración es adecuada para la selección. Con esta concentración se impide la formación de brotes, aunque los callos no mueren completamente. Por otra parte, se estableció que el protocolo de regeneración utilizado es de baja eficiencia y, por consiguiente, es necesario optimizarlo para poder usarlo en procesos de ingeniería genética de cultivares colombianos de arroz.

An efficient selection system is one of the most important elements of plant genetic engineering. The purpose of this study was to evaluate the sensitivity of scutellum-derived embriogenic calli obtained from three colombian rice varieties (FEDEARROZ 2000, FEDEARROZ 50 and FEDEARROZ 369), to the selection marker hygromycin B. Aditionally, the response of these varieties to the regeneration protocol was measured. Four antibiotic concentrations were tested (25 mg/L, 50 mg/L, 75 mg/L and 100 mg/L) plus one control without hygromycin B. The results show that 50 mg/L of antibiotic in the regeneration medium is adequate for selection. This concentration prevents the formation of shoots, though the calli do not die. It was also established that the regeneration protocol is a low-efficiency system and it needs to be improved, in order to use it for colombian rice genetic engineering.

Perspectivas del uso de bacterias rizosféricas en el control de Pyricularia grisea (Cooke Sacc) en el cultivo del arroz (Oryza sativa L) / Prospect of the use of bacteria in the control Pyricularia grisea (Cooke Sacc) on rice (Oriza sativa L)

El arroz es fuente de alimento para una gran parte de la población mundial, con alto promedio de consumo anual. En este cultivo las enfermedades de origen microbiano constituyen uno de los factores que inciden en la obtención de bajos rendimientos y calidad de los granos. La piriculariosis o añublo del arroz, causada por Pyricularia grisea, es la enfermedad más importante en este cultivo en América Latina, ya que puede provocar hasta el 100% de reducción de los rendimientos. Como parte de la estrategia de agricultura sostenible, se trata de controlar estos patógenos y lograr altos rendimientos del cultivo mediante una combinación adecuada de fertilizantes químicos y productos biológicos. En este sentido, la aplicación de inoculantes bacterianos constituidos por bacterias promotoras del crecimiento vegetal (Plant Growth- Promoting Bacteria, PGPB, por sus siglas en inglés) ha constituido una alternativa ecológica que favorece la conservación del medioambiente y el ecosistema. Este trabajo tiene como objetivo abordar el estado actual y las perspectivas de uso de bacterias rizosféricas en el control de Pyricularia grisea en el cultivo del arroz, tratando algunos temas relevantes, como son las principales enfermedades que afectan al cultivo, los géneros de PGPB más utilizados para el control de las mismas y sus principales mecanismos de acción.

Rice is an important food supply for a large part of the world population and its consumption rates are very high. Microbial diseases are one of the main causes that provoke low yields and low-quality spotted grains. Although fungi, bacteria and viruses are mostly the responsible for these losses, fungal diseases strike more frequently. Among fungi, Pyricularia grisea, the blast fungus is responsible for up to 100% of reduction in yields, being the blast the most important rice disease in Latin America. To control this pathogen, a strategy of sustainable agriculture might be developed, combining accurately chemical and biological products. PGPB based bioproducts have been considered as an eco-friendly alternative, which favours environment preservation. This work was aimed to approach the current status and outlook of the use of rhizobacteria in the biocontrol of Pyricularia grisea on rice. Main diseases attacking rice, most beneficial PGPB and its mechanisms of action will be discussed too in this review.

Colonization of rice and Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) larvae by genetically modified endophytic Methylobacterium mesophilicum

The colonization of Spodoptera frugiperda J.E. Smith larvae and rice seedlings by genetically modified endophytic bacterium Methylobacterium mesophilicum, and also the possible transfer of this bacterium to inside the larva's body during seedlings consumption were studied. The data obtained by bacterial reisolation and fluorescence microscopy showed that the bacterium colonized the rice seedlings, the larva's body and that the endophytic bacteria present in seedlings could be acquired by the larvae. In that way, the transference of endophytic bacterium from plants to insect can be a new and important strategy to insect control using engineered microorganisms.

Micobiota e micotoxinas em amostras de arroz coletadas durante o sistema estacionário de secagem e armazenamento / Mycobiota and mycotoxins in rice samples collected during the stationary drying and storage system

Considerando as perdas qualitativas e quantitativas no período pós-colheita de grãos, neste trabalho foram avaliadas a contaminação fúngica e as micotoxinas em arroz com casca, durante o sistema estacionário de secagem e armazenamento. As amostras foram coletadas em intervalos de 60 dias durante o armazenamento, em duas alturas do silo-secador. A amostra inicial apresentou 5,4x10(4)UFC g-1, sendo que a contagem aumentou significativamente durante a secagem e o armazenamento, chegando a 10(5)UFC g-1. A contaminação fúngica diferiu no interior do silo-secador, com maior contaminação na porção superior do silo. Os gêneros predominantes foram Aspergillus e Penicillium, com maior ocorrência de A. flavus (26,3 por cento) e P. commune (19,1 por cento). Quatro isolados de A. flavus produziram aflatoxina B1, mas não foram detectadas micotoxinas nas amostras.

Considering the qualitative and quantitative losses in post-harvest of grain, in this research was evaluated fungi and mycotoxins contamination in whole rice (Oryza sativa L.) during the stationary drying and storage system. Samples were collected in a period of sixty days in two heights of the warehouse during storage. The initial sample presented 5.4x10(4)CFU g-1; the contamination increased significantly during drying and storage, up to 10(5)CFU g-1. Fungi contamination was different inside the warehouse with higher contamination in the upper portion. The more abundant fungi genera were Aspergillus and Penicillium, A. flavus (26.3 percent) and P. commune (19.1 percent) which presented higher incidence. Aflatoxin B1 was produced by four A. flavus isolates, but mycotoxins were not detected in the samples.

[Isolation and serotyping of endemic leptospires of eastern part of flat area of Guilan province, Iran]

Leptospirosis is a zoonosis that is more common in tropical and semitropical regions and is endemic in Guilan province. In endemic region, only a limited number of pathogenic serovars are common, characterization of them is very important step in detecting the main reservoir [s] of the disease. This study was performed to isolate leptospires from rice farms, irrigation canals and rivers of eastern part of flat area of Guilan province to detect main endemic serotypes of leptospirosis. In this descriptive and cross - sectional study samples were taken from 8 cities of the area of Guilan province, Noth of Iran between May to September of 2007. Two ml of any processed water sample was inoculated in liquid EMJH medium with 200 micro g/ml 5-flurouracil after filtration, were incubated in 30°C for 3 monthes, and were checked by darkfiel microscopy every two weeks. All positive samples were serotyped by using 30 type antisera which were main representative of serogroups. 47 of 320 specimens were positive and 273 samples were negative. One saprophytic specie [Biflexa] including two serogroups [Andamana, and Semaranga] and three pathogenic species [Interrogans, Kireshnerii, and Boirgpetersenii] including 6 serogroups were detected Icterohaemorrhagiae, Pomona, and canicola of interrogans, Hardjobovis and Sejroea of Borgpeterseni pecie, Grippotyphosa of KircshnerL Non-pathogenic serogroups were found from surface water, but the pathogenic serogroup were detected only from rice farm water. The high incidence of leptospirosis in rual area concide with seasonal rice cultivation, which can be due to trafic of domestic animal in rice farms and elevation temprature, and activity of rice farm water with subsequent presence of pathogenic type and serotypes in rice farm

Endophytic colonization of rice (Oryza sativa L.) by the diazotrophic bacterium Burkholderia kururiensis and its ability to enhance plant growth

Burkholderia kururiensis is a diazotrophic bacterium originally isolated from a polluted aquifer environment and presents a high level of similarity with the rice endophyte "B. brasilensis" species. This work assessed the ability of B. kururiensis to endophytically colonize rice plantlets by monitoring different tissues of root-inoculated plants for the presence of bacterial growth in different media, electron microscopy and by 16S rDNA analysis. Observations of roots, stems and leaves of inoculated rice plantlets by electron microscopy revealed B. kururiensis colonization predominantly on root hair zones, demonstrating endophytic colonization primarily through the endodermis, followed by spreading into xylem vessels, a possible pathway leading to aerial parts. Although indifferent for the bacterial growth itself, addition of a nitrogen source was a limiting factor for endophytic colonization. As endophytic colonization was directly associated to an enhanced plant development, production of phytohormone auxin/indole-3-acetic acid by B. kururiensis was assayed with transgenic rice plantlets containing an auxin-responsive reporter (DR5-GUS). Our findings suggest the ability of auxin production by plant-associated B. kururiensis which may have a stimulatory effect on plant development, as evidenced by activation of DR5-GUS. We hereby demonstrate, for the first time, the ability of B. kururiensis to endophytically colonize rice, promoting both plant growth and rice grain yield.

Burkholderia kururiensis é uma bactéria diazotrófica, originalmente isolada de um ambiente aquático poluído e apresenta alto nível de similaridade com a espécie endofítica "B. brasilensis" encontrada na planta de arroz. Este artigo demonstrou a habilidade de B. kururiensis colonizar endofiticamente plântulas de arroz, após esta bactéria ter sido inoculada na raiz das plantas. Esta capacidade foi confirmada pelo crescimento bacteriano em diferentes tecidos da planta, por microscopia eletrônica e pela análise do 16S rADN. Observação por microscopia eletrônica das raízes, caule e folhas das plântulas de arroz inoculadas, revelou predominância da colonização de B. kururiensis na zona pilífera da raiz, demonstrando que a colonização endofítica inicia-se na endoderme, espalha-se pelo xilema, sendo esta a possível via para a bactéria alcançar as partes aéreas. A adição de uma fonte de nitrogênio, embora não tenha influenciado no crescimento bacteriano, foi um fator limitante para a colonização endofítica. Como a colonização endofítica mostrou-se diretamente associada ao aumento no desenvolvimento da planta, a produção do fitohormônio auxina/ácido 3-indolacético pela B. kururiensis foi verificada utilizando uma plântula de arroz transgênica, contendo o repórter responsivo para auxina (DR5-GUS). Nossos resultados sugerem que a produção de auxina pela B. kururiensis é responsável pelo estímulo no desenvolvimento da planta verificado pela ativação do DR5-GUS. Neste trabalho demonstramos, pela primeira vez, a habilidade de B. kururiensis colonizar endofiticamente a planta de arroz, promovendo tanto o aumento no crescimento da planta como a produção de sementes de arroz.