Bacillus mycoides y ácidos húmicos como bioestimulantes de fríjol caupí bajo estrés por salinidad

Los bioestimulantes tienen gran potencial en la agricultura, no solo por aumentar el crecimiento de las plantas, sino porque también promueven la tolerancia frente a diferentes tipos de estrés. En este estudio, se evaluó el efecto de dos bioestimulantes Bacillus mycoides, inmovilizado en perlas de alginato y ácidos húmicos (AH), en plantas de fríjol caupí, cultivadas en un suelo salino, bajo los siguientes tratamientos: 1) solución de AH, mediante aspersión foliar, 2) suspensión de B. mycoides, inmovilizado en perlas aplicado en la rizósfera y 3) solución de AH + suspensión de B. mycoides inmovilizado; el tratamiento control fueron plantas sin aplicación de bioestimulantes. Se determinó el contenido hídrico relativo, el índice de contenido de clorofila, además del contenido de prolina y polifenoles, como indicadores de tolerancia al estrés. El tratamiento 3 generó un aumento de 11,27 % en el contenido hídrico relativo, mientras que con el tratamiento 2, se observó un incremento significativo del 48,33 %, en el índice de contenido de clorofila y del 49,07 %, en el contenido de prolina, lo cual, se sugiere la estimulación de mecanismos de tolerancia frente al estrés salino. La activación de estos mecanismos, observada con tratamientos que incluyen la inmovilización de B. mycoides, sugiere que esta forma de aplicación de la bacteria puede contribuir a mejorar las condiciones de crecimiento de plantas de fríjol caupí sometidas a estrés salino y puede ser probada en otras plantas de interés agrícola, en regiones afectadas por la salinidad.

Biostimulants have great potential in agriculture enhancing plant growth as well as stimulating tolerance to different types of stress. In this study, the effect of two biostimulants, Bacillus mycoides immobilized in alginate beads and humic acids (HA), was evaluated in cowpea plants grown in saline soil, following treatments were evaluated: 1) HA solution applied through foliar spray, 2) suspension of immobilized B. mycoides in beads applied around in the rhizosphere and 3) HA solution + immobilized B. mycoides suspension. Plants without biostimulant application were considered as control treatment. Relative water content (RWC), chlorophyll content index (CCI), proline, and polyphenol content were determined as indicators of stress tolerance mechanisms expression. Treatment 3 generated an increase of 11.27 % in RWC, while with treatment 2 a significant increase of 48.33 % in CCI and 49.07 % in proline content was observed; these results suggest the stimulation of tolerance mechanisms against salt stress. Effects exhibited after the treatments with immobilized B. mycoides suggest that this way of application of the bacteria can contribute to improving the growth and adaption of cowpea plants subjected to salt stress and can be tested in other plants of agricultural interest over saline stress affection.

Production of humic substances through coal-solubilizing bacteria

In this paper, the production of humic substances (HS) through the bacterial solubilization of low rank coal (LRC) was evaluated. The evaluation was carried out by 19 bacterial strains isolated in microenvironments with high contents of coal wastes. The biotransformed LRC and the HS produced were quantified in vitro in a liquid growth medium. The humic acids (HA) obtained from the most active bacterial strain were characterized via elemental composition (C, H, N, O), IR analyses, and the E4/E6 ratio; they were then compared with the HA extracted chemically using NaOH. There was LRC biotransformation ranged from 25 to 37%, and HS production ranged from 127 to 3100 mg.L-1. More activity was detected in the isolated strains of Bacillus mycoides, Microbacterium sp, Acinetobacter sp, and Enterobacter aerogenes. The HA produced by B. mycoides had an IR spectrum and an E4/E6 ratio similar to those of the HA extracted with NAOH, but their elemental composition and their degree of aromatic condensation was different. Results suggest that these bacteria can be used to exploit the LRC resulting from coal mining activities and thus produce HS in order to improve the content of humified organic matter in soils.

Isolation and Identification of the Immunopotentiating Compound Prepared from the Metabolites of Bacillus Mycoides / 微生物学通报

An immunopotentiating compound has been isolated from the metabolites of Bacillus mycoides under the bioassay-guided isolation and identification for its immunopotentiating effect and chemical structure. The isolation and purification of the compound were consisted of macroporous adsorptive resins, silicagel chromatographic column and Sephadex G-200 chromatographic column. The immunopotentiating effect was assayed in every step isolation. At last, the only substance having the strongest immunopotentiating effect had been isolated and purified. Through the procedure consisiting of Ultra-Violet spectroscopy (UV), IR (Infrared Radiation), Time of Flight Mass Spectrum (TOF-MS), Nuclear Magnetic Resonance (NMR) and Element analysis, the possible structure of compound M had been identified as cyclic (Pro-Gly) dipeptide (C7H10O2N2) (Diketopiperazine). To be determined the immunopotentiating effect, the mice were treated by intraperitoneal injection of cyclic (Pro-Gly) dipeptide in the treatment group and physiologic saline in the control group. At the 14th day after the injection, the SOD activity and the phagocytosis activities reached the peak value and were significantly higher than those in control group. At the 21st day, the bactericidal activity reached peak value and was significantly higher than that in the control group. From the above results, we concluded that the main active component enhancing the immunity of mice was cyclic (Pro-Gly) dipeptide in the metabolism of Bacillus mycoides.