Abstract Background: Deficiency in sorghum growth in ecosystems of low-nutrient soils has been scarcely studied. This soil deficiency can be overcome by the addition of plant growth-promoting bacteria which increase sorghum growth. Questions and/or Hypotheses: indole acetic acid (IAA) producing and phosphate solubilizing bacteria can promote sorghum growth under nutritional stress. Studied species: Sorghum bicolor (L.) Moench. Study site and dates: Mexico City, 2018. Methods: Of the twelve bacterial strains utilized, three produce IAA (group BI), two strains produce IAA and siderophores (BIS group), four strains produce IAA and solubilize phosphate (BIP group), and three strains produce IAA, solubilize phosphate, and produce siderophores (BIPS group). Hydroponic bioassays and low-nutrient soil bioassay were used. Results: In hydroponic bioassays, for BI and BIS groups, five strains significantly increased the growth parameters with respect to the control, and for the BIP and BIPS groups, two strains promoted stem development and shoot dry weight. In a low-nutrient soil bioassay, Pseudomonas sp. BI-1 (from BI group) was the one that presented the highest percentages 32, 48, 140 and 79 % in stem diameter, height and dry weight of the shoot and dry weight of the root, respectively, followed by the P. mohnii BIPS-10 strain (from BIPS group) that exhibited similar results. Conclusions: IAA producing Pseudomonas strains improve the sorghum growth in a low-nutrient soil and suggest that Pseudomonas sp. BI-1 and P. mohnii BIPS-10 could be used as potential bioinoculants for sorghum.

Resumen Antecedentes: La deficiencia en el crecimiento del sorgo en suelos con nutrientes escasos es poco estudiada. Esta deficiencia puede superarse mediante la adición de bacterias promotoras del crecimiento vegetal que aumentan el crecimiento del sorgo. Preguntas y/o hipótesis: bacterias que producen ácido indol acético (IAA) y solubilizan fosfato promueven el crecimiento del sorgo bajo estrés nutricional. Especies de estudio: Sorghum bicolor (L.) Moench. Sitio y años de estudio: Ciudad de México, 2018. Métodos: de doce bacterias utilizadas, tres producen IAA (grupo BI), dos producen IAA y sideróforos (grupo BIS), cuatro producen IAA y solubilizan fosfato (grupo BIP), y tres producen IAA, solubilizan fosfato y producen sideróforos (grupo BIPS). Bioensayos hidropónicos y bioensayos en suelo con nutrientes escasos fueron empleados. Resultados: en los bioensayos hidropónicos, para los grupos BI y BIS, cinco cepas incrementaron significativamente los parámetros de crecimiento con respecto al control, y para los grupos BIP y BIPS, dos cepas promovieron el desarrollo del tallo y el peso seco del brote. En los bioensayos con suelo con nutrientes escasos, Pseudomonas sp. BI-1 (del grupo BI) presentó los porcentajes más altos 32, 48, 140 y 79 % en el diámetro del tallo, altura y peso seco del brote y peso seco de la raíz, respectivamente, seguido de P. mohnii BIPS-10 (del grupo BIPS). Conclusiones: Pseudomonas productoras de IAA mejoran el crecimiento del sorgo en un suelo con nutrientes escasos, sugiriendo que Pseudomonas sp. BI-1 y P. mohnii BIPS-10 podrían usarse como bioinoculantes potenciales para el sorgo.

Abstract: Background: Cerro de la Estrella (CE) is a natural reserve in Mexico City that suffers from afforestation, and its restoration with Acacia farnesiana is being considered. Question: Will the nodule-forming rhizobia and arbuscular mycorrhizal fungi (AMF) associated with the CE soil support A. farnesiana growth? Study species: Acacia farnesiana (L.) Willd. (Fabaceae). Methods: Mycorrhizal fungi, nodule-forming rhizobia and physicochemical characteristics of the CE soil were studied to determine if they are suitable for improving the growth of Acacia farnesiana. Results: Four different families of AMF were found which generated 13 % mycorrhization with A. farnesiana. However, A. farnesiana from CE did not nodulate, suggesting the lack of native rhizobia. The CE soil has low fertility. Nodules of A. farnesiana were obtained from the soil in Ticuman, Morelos, and 66 rhizobia were isolated from them. Rhizobium isolates were individually added to A. farnesiana grown in the CE soil. Five of the 66 isolates yielded significant differences in shoot dry weight, shoot height, number of nodules, nodulation time and nitrogenase activity compared with the Sinorhizobium americanum CFNEI 156 control strain (p < 0.05). Three isolates were named as S. americanum ENCBTM1, ENCBTM31 and ENCBTM43, and last two as Sinorhizobium sp. ENCBTM34 and ENCBTM45. Conclusions: CE soil had low fertility and lacked specific rhizobia for A. farnesiana. The individual addition of S. americanum (ENCBTM1, ENCBTM31 or ENCBTM43) or Sinorhizobium sp. (ENCBTM34 or ENCBTM45) improved the growth of A. farnesiana.

Resumen: Antecedentes: El Cerro de la Estrella (CE) es una reserva natural deforestada en la Ciudad de México cuya restauración con Acacia farnesiana es considerada. Pregunta: ¿Los rizobios nodulantes y los hongos micorrízicos arbusculares (HMA) del CE apoyarán el crecimiento de A. farnesiana? Especies de estudio: Acacia farnesiana (L.) Willd. (Fabaceae). Métodos: Se estudiaron los HMA, los rizobios nodulantes y las características fisicoquímicas del suelo del CE para determinar si mejoran el crecimiento de A. farnesiana. Resultados: Cuatro familias de HMA generan 13 % de micorrización con A. farnesiana. La planta no noduló creciendo en suelo del CE sugiriendo la falta de rizobios nativos. El suelo del CE tiene una baja fertilidad. Nódulos de A. farnesiana se obtuvieron de Ticuman, Morelos y 66 rizobios se aislaron de ellos, los cuales se analizaron individualmente en A. farnesiana empleando suelo del CE y solo cinco produjeron diferencias significativas en el peso seco, altura del brote, el número de nódulos, el tiempo de nodulación y la actividad de la nitrogenasa en comparación con la cepa control Sinorhizobium americanum CFNEI 156 (p < 0.05). Tres aislados fueron identificados como S. americanum ENCBTM1, ENCBTM31 y ENCBTM43, y dos como Sinorhizobium sp. ENCBTM34 y ENCBTM45. Conclusiones: El suelo CE tiene baja fertilidad y carece de rizobios específicos para A. farnesiana. La adición individual de S. americanum (ENCBTM1, ENCBTM31 o ENCBTM43) o Sinorhizobium sp. (ENCBTM34 o ENCBTM45) mejoró el crecimiento de A. farnesiana.

Background: Methyl tert-butyl ether (MTBE) is a pollutant that causes deleterious effects on human and environmental health. Certain microbial cultures have shown the ability to degrade MTBE, suggesting that a novel bacterial species capable of degrading MTBE could be recovered. The goal of this study was to isolate, identify and characterize the members of a bacterial consortium capable of degrading MTBE. Results: The IPN-120526 bacterial consortium was obtained through batch enrichment using MTBE as the sole carbon and energy source. The cultivable fraction of the consortium was identified; of the isolates, only Stenotrophomonas maltophilia IPN-TD and Sphingopyxis sp. IPN-TE were capable of degrading MTBE. To the best of our knowledge, this report is the first demonstrating that S. maltophilia and Sphingopyxis sp. are capable of degrading MTBE. The degradation kinetics of MTBE demonstrated that S. maltophilia IPN-TD had a significantly higher overall MTBE degradation efficiency and rate (48.39 ± 3.18% and 1.56 ± 0.12 mg L-1 h-1, respectively) than the IPN-120526 consortium (38.59 ± 2.17% and 1.25 ± 0.087 mg L-1 respectively). The kinetics of MTBE removal by both cultures fit first-order and pseudo-first-order reaction models. Conclusions: These findings suggest that S. maltophilia IPN-TD in axenic culture has considerable potential for the detoxification of MTBE-contaminated water.

Conventional microbiological culture techniques are frequently insufficient to confirm endophthalmitis clinical cases which could require urgent medical attention because it could lead to permanent vision loss. We are proposing PCR-DGGE and 16S rRNA gene libraries as an alternative to improve the detection and identification rate of bacterial species from endophthalmitis cases.