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The capacity of four bacterial strains isolated from productive soil potato fields to solubilize tricalcium phosphate on Pikovskaya agar or in a liquid medium was evaluated. A bacterial strain was selected to evaluate in vitro capacity of plant-growth promotion on Solanum tuberosum L. culture. Bacterial strain A3 showed the highest value of phosphate solubilization, reaching a 20 mm-diameter halo and a concentration of 350 mg/l on agar and in a liquid medium, respectively. Bacterial strain A3 was identified by 16S rDNA analysis as Bacillus pumilus with 98% identity; therefore, it is the first report for Bacillus pumilus as phosphate solubilizer. Plant-growth promotion assayed by in vitro culture of potato microplants showed that the addition of bacterial strain A3 increased root and stems length after 28 days. It significantly increased stem length by 79.3%, and duplicated the fresh weight of control microplants. In this paper, results reported regarding phosphorus solubilization and growth promotion under in vitro conditions represent a step forward in the use of innocuous bacterial strain biofertilizer on potato field cultures.

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Supplementation of Selenium (Se) can improve the oxidative stability of meat products and retard metmyoglobin formation; so prolonging color. Effect of organic Se addition in the diets of sheep on meat stability; color and pH are limited and need to be studied. A study was conducted with eighteen Pelibuey female sheep at the finishing stage, and supplemented with organic Se-enriched Saccharomyces cerevisiae for sixty days to evaluate its effect on color and pH of Longissimus dorsi muscle. The research was conducted in a block randomized design considering three treatments; control (Se0) without the addition of yeast, or with 0.35 ppm of yeast (Se34) or with 0.60 ppm (Se59). Sheep were slaughtered at an average weight of 39.5 ± 4.41 kg. Meat color and pH were recorder in the cold carcass, 24 h after slaughtering, and during shelf life at 0, 4, 6 and 8 days after slaughtering under refrigeration at 4 °C. No significant differences were observed (P>0.05) for meat color and pH characteristics due to treatment. Decreased redness (a*) and Chroma (C*) values due to storage time were observed; however, the yellowness (b*) and angle Hue were increased. It could be concluded that supplementation of Seenriched yeast in finishing sheep with 0.35 ppm and 0.60 ppm has no effect on meat color and pH characteristics.

Phosphate-solubilizing bacteria (PSB) transform precipitated inorganic phosphorus into soluble orthophosphates. This study evaluated the efficiency of tricalcium and iron phosphate solubilization in Pikovskaya medium using five bacterial strains (A1, A2, A3, A5, and A6) cultured in acidic and alkaline pH levels. The bacterial strain that proved to be more efficient for P solubilization and was tolerant to pH variations was selected for assessing bacterial growth and P solubilization with glucose and sucrose in the culture medium. The bacterial strains were identified through 16S rRNA gene sequencing as Pseudomonas libanensis A1, Pseudomonas libanensis (A2), Bacillus pumilus (A3), Pseudomonas libanensis (A5), and Bacillus siamensis (A6). These five bacterial strains grew, tolerated pH changes, and solubilized inorganic phosphorus. The bacterial strain A3 solubilized FePO4 (4 mg L−1) and Ca3(PO4)2 (50 mg L−1). P solubilization was assayed with glucose and sucrose as carbon sources for A3 (Bacillus pumilus MN100586). After four culture days, Ca3(PO4)2 was solubilized, reaching 246 mg L−1 with sucrose in culture media. Using glucose as a carbon source, FePO4 was solubilized and reached 282 mg L−1 in six culture days. Our findings were: Pseudomonas libanensis, and Bacillus siamensis, as new bacteria, can be reported as P solubilizers with tolerance to acidic or alkaline pH levels. The bacterial strain B. pumilus grew using two sources of inorganic phosphorus and carbon, and it tolerated pH changes. For that reason, it is an ideal candidate for inorganic phosphorus solubilization and future production as a biofertilizer.

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La aplicación de agroquímicos en la floricultura, disminuye gradualmente la fertilidad y poblaciones de microorganismos benéf icos del suelo, siendo los actinomicetos indicadores biológicos de la calidad edáf ica. En el presente artículo se propuso como objetivo comparar los cambios en la densidad poblacional de actinomicetos en suelos florícolas de rosa, clavel y agapando, y su tratamiento con vermicomposta. Los tratamientos fueron agapando como control, suelo con plaguicida del cultivo de rosa, suelo con plaguicida del cultivo de clavel, suelo con plaguicida del cultivo de rosa adicionado con vermicomposta a 40 Mg ha-1 y suelo con plaguicida del cultivo de clavel adicionado con vermicomposta a 40 Mg ha-1. Durante 28 días, se cuantif icó la densidad de población de actinomicetos totales, por el método de conteo en placa. Los suelos florícolas son de textura franco-arenosa, por su bajo contenido en materia orgánica, se adicionó vermicomposta a los tratamientos. La población de actinomicetos totales de los suelos florícolas y vermicomposta fue del orden de 1 × 105 UFC g-1 de suelo, lo que indicó un bajo contenido. Se detectaron cambios en la densidad poblacional de actinomicetos en los tratamientos de suelos florícolas de rosa y clavel con y sin vermicomposta, siendo mayor en los suelos florícolas de rosa y clavel sin la adición de vermicomposta. Los cambios en la población de actinomicetos de los suelos cultivados con rosa y clavel indican que estos microorganismos están adaptados a la aplicación de plaguicidas. La adición de vermicomposta mejoró las propiedades f isicoquímicas de los suelos florícolas en sus respectivos tratamientos.