Biostimulants constitute an emerging group of crop management products used to enhance productivity under abiotic stress conditions. The ability of some biostimulant products, such as seaweed extracts (SE), to enhance crop tolerance to salinity stress has been documented. SE contain a series of bioactive compounds and signaling molecules, as well as mineral and organic nutrients, that greatly benefit plants. A greenhouse experiment was conducted in order to evaluate SE-mediated tolerance mechanisms in tomato plants under salinity stress. The experiment was divided into two developmental phases (vegetative and reproductive) and included four treatments: control (plants with neither treatment), SE (plants treated with seaweed extract), NaCl (plants irrigated with 300 mM NaCl), and SE + NaCl (plants treated with seaweed extract and irrigated with 300 mM NaCl). Tomato plants treated with the SE from Padina gymnospora showed an increase in root and shoot length (18 cm and 13 cm), root and shoot area (33 cm² and 98 cm²), and shoot and root fresh weight (1.0 and 3.8 g) under the control and salinity stress conditions. The decrease in productivity (number of fruits) associated with salinity stress was reduced from 28.7% to only 3.4% in SE-treated plants. The positive effects of SE application also included early flowering and enhanced fruit weight and quality. Our findings suggest that optimized photosynthetic performance and antioxidant defense systems (proline, total phenols, and flavonoids) appear to be major factors modulating SE responses to salinity tolerance in tomato plants with promising agricultural applications.

Se realizó el estudio de la bioactividad de las Actinobacterias cultivables a partir de sedimento marino de la Bahía de Todos Santos, México, y se identificaron mediante las secuencias del gen 16S ARNr. Las cepas bacterianas fueron cultivadas en 1 L de medio líquido A1 y se constató su crecimiento en presencia de agua de mar. Los extractos orgánicos de los cultivos se extrajeron con Amberlita XAD-7 eluida con acetona. Los extractos fueron separados por cromatografía en gel de sílice C-18. Los extractos crudos y las fracciones se probaron contra células de cáncer de colon HCT-116. En total, 26 cepas fueron cultivadas e identificadas, divididas en 10 unidades taxonómicas operacionales (UTOs) con 100% de identidad de sus secuencias, representando tres familias del orden Actinomycetales, pertenecientes a los géneros Streptomyces (77%), Micromonospora (20%) y Nocardia (3%); 6 de éstos UTOs no habían sido reportados previamente. Diecinueve por ciento de los extractos crudos del género Streptomyces mostraron actividad citotóxica en un rango de IC50 de 69,0 a ≤ 0,076 mg·-1. Las fracciones más activas contenían los compuestos monactin y derivados de pamamicina, los cuales fueron identificados por su peso molecular y sus patrones de fragmentación.

From their chemical nature to their ecological interactions, coral reef ecosystems have a lot in common with highly productive terrestrial ecosystems. While plants are responsible for primary production in the terrestrial sphere, the photosynthetic endosymbionts of corals are the key producers in reef communities. As in plants, coral microbiota have been suggested to stimulate the growth and physiological performance of the photosynthetic endosymbionts that provide energy sources to the coral. Among them, actinobacteria are some of the most probable candidates. To explore the potential of coral actinobacteria as plant biostimulants, we have analyzed the activity of Salinispora strains isolated from the corals Porites lobata and Porites panamensis, which were identified as Salinispora arenicola by 16S rRNA sequencing. We evaluated the effects of this microorganism on the germination, plant growth, and photosynthetic response of wild tobacco (Nicotiana attenuata) under a saline regime. We identified protective activity of this actinobacteria on seed germination and photosynthetic performance under natural light conditions. Further insights into the possible mechanism showed an endophytic-like symbiosis between N. attenuata roots and S. arenicola and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity by S. arenicola. We discuss these findings in the context of relevant ecological and physiological responses and biotechnological potential. Overall, our results will contribute to the development of novel biotechnologies to cope with plant growth under saline stress. Our study highlights the importance of understanding marine ecological interactions for the development of novel, strategic, and sustainable agricultural solutions.

Resumen.-La actinobacteria marina AMS370, identificada mediante comparación de las secuencias del gen 16S del ARNr como Salinispora arenicola, fue aislada a partir de sedimento del Golfo de California, México. De su extracto semi-polar, se aislaron 8 compuestos conocidos: ácido-4-Hidroxi-fenil acético (1), 5-Metil-2-metilen-2,3-dihidro-1H-pirimidin-4-ona (2), 1H-Pirimidin-2,4-diona (3), ácido-3-amino-5-hidroxi-benzoico (4), 2-(4-Amino-imidazol-[4,5-d]piridazin-1-il)-5-hidroximetil-4-metil-tetrahidrofuran-3-ol (5), Acrilato de 3-(4-Hidroxi-genil)-metilo (6), 3-Bencil-6-isobutil-piperazin-2,5-diona (7) y 5,8-epidioxi-(22E,24R)ergosta-6,22-dien-3-ol (Peróxido de Ergosterol) (8). La identificación química fue realizada mediante comparación de sus espectros de RMN con los espectros de los compuestos originales. Ésta sería la primera ocasión que el compuesto 4 se reporta como un producto natural a partir del género Salinispora. El extracto crudo y todas sus

Actinobacteria produce many bioactive compounds currently used as antibiotics and anticancer drugs. The objective of this project was to evaluate the Gulf of California as a novel source of bioactive actinobacterial strains. A total of 235 actinobacterial strains were isolated from marine sediment collected in Concepción and los Ángeles bays (Mexico). Based on their morphology, seawater requirements, and 16S rRNA sequencing, actinobacterial strains were classified as Streptomyces, Micromonospora, and Salinispora. Sixty-nine organic and aqueous extracts were obtained using liquid-liquid extraction with ethyl acetate; 17 showed cytotoxic activity against breast cancer cells (MCF7) and cervical cancer cells (HeLa). The highest activity values observed, expressed as survival percentage, were 20–25% against MCF7 cells (strains S-365, S-355, and S-361) and 24–25% against HeLa cells (strains S-165, S-361, and S-353). Only three aqueous extracts showed antibiotic activity towards methicillin-resistant Staphylococcus aureus, with activity values of 3% and 6% for strains S-370 and S-369, respectively. Molecular weights found by liquid chromatography-mass spectrometry analysis are reported for Micromonospora species isolated from soil, but no species specific secondary metabolite evidence was observed for Salinispora isolates. The biological activity observed in this work offers opportunities for further chemical studies to define the compounds responsible for this activity in order to contribute to the discovery of new drugs and to acknowledge the Gulf of California as a reservoir of marine bioactive actinobacteria strains that are important for human health.