Biostimulant Capacity of an Enzymatic Extract From Rice Bran Against Ozone-Induced Damage in Capsicum annum

Ozone is a destructive pollutant, damaging crops, and decreasing crop yield. Therefore, there is great interest in finding strategies to alleviate ozone-induced crop losses. In plants, ozone enters leaves through the stomata and is immediately degraded into reactive oxygen species (ROS), producing ROS stress in plants. ROS stress can be controlled by ROS-scavenging systems that include enzymatic or non-enzymatic mechanisms. Our research group has developed a product from rice bran, a byproduct of rice milling which has bioactive molecules that act as an antioxidant compound. This product is a water-soluble rice bran enzymatic extract (RBEE) which preserves all the properties and improves the solubility of proteins and the antioxidant components of rice bran. In previous works, the beneficial properties of RBEE have been demonstrated in animals. However, to date, RBEE has not been used as a protective agent against oxidative damage in agricultural fields. The main goal of this study was to investigate the ability of RBEE to be used as a biostimulant by preventing oxidative damage in plants, after ozone exposure. To perform this investigation, pepper plants (Capsicum annuum) exposed to ozone were treated with RBEE. RBEE protected the ozone-induced damage, as revealed by net photosynthetic rate and the content of photosynthetic pigments. RBEE also decreased the induction of antioxidant enzyme activities in leaves (catalase, superoxide dismutase, and ascorbate peroxidase) due to ozone exposure. ROS generation is a common consequence of diverse cellular traumas that also activate the mitogen-activated protein kinase (MAPK) cascade. Thus, it is known that the ozone damages are triggered by the MAPK cascade. To examine the involvement of the MAPK cascade in the ozone damage CaMPK6-1, CaMPK6-2, and CaMKK5 genes were analyzed by qRT-PCR. The results showed the involvement of the MAPK pathway in both, not only in ozone damage but especially in its protection by RBEE. Taken together, these results support that RBEE protects plants against ozone exposure and its use as a new biostimulant could be proposed

Safe Cultivation of Medicago sativa in Metal-Polluted Soils from Semi-Arid Regions Assisted by Heatand Metallo-Resistant PGPR

Soil contamination with heavy metals is a constraint for plant establishment and development for which phytoremediation may be a solution, since rhizobacteria may alleviate plant stress under these conditions. A greenhouse experiment was conducted to elucidate the effect of toxic metals on growth, the activities of ROS (reactive oxygen species)-scavenging enzymes, and gene expression of Medicago sativa grown under different metal and/or inoculation treatments. The results showed that, besides reducing biomass, heavy metals negatively affected physiological parameters such as chlorophyll fluorescence and gas exchange, while increasing ROS-scavenging enzyme activities. Inoculation of M. sativa with a bacterial consortium of heat- and metallo-resistant bacteria alleviated metal stress, as deduced from the improvement of growth, lower levels of antioxidant enzymes, and increased physiological parameters. The bacteria were able to effectively colonize and form biofilms onto the roots of plants cultivated in the presence of metals, as observed by scanning electron microscopy. Results also evidenced the important role of glutathione reductase (GR), phytochelatin synthase (PCS), and metal transporter NRAMP1 genes as pathways for metal stress management, whereas the gene coding for cytochrome P450 (CP450) seemed to be regulated by the presence of the bacteria. These outcomes showed that the interaction of metal-resistant rhizobacteria/legumes can be used as an instrument to remediate metal-contaminated soils, while cultivation of inoculated legumes on these soils is still safe for animal grazing, since inoculation with bacteria diminished the concentrations of heavy metals accumulated in the aboveground parts of the plants to below toxic levelsMarruecos. Centre National pour la Recherche Scientifique et Technique (CNRST)-España, Ministerio de Economía y Competitividad (MINECO)-PPR2 /2016/42Unión Europea (FEDER)-CGL2016-75550-

Innovative compounds to battle multirresistance to antibiotics: use of pva-tannic acid nano- particles to inhibit staphylococcus pseudintermedius growth

Antibiotic resistance is an increasing public health problem that affects to numerous pathogens, including Staphylococcus pseudintermedius, which has a high prevalence of methicillin resistance and can be transmitted to humans. The development of new compounds to prevent the appearance of antibiotic resistances and find alternatives to classic therapies is essential to health protection. The main objective of the present study is to determine whether the nanoparticles of polyvinyl alcohol and tannic acid “PVA-TA NPs” are effective to inhibit Staphylococcus pseudintermedius and can be considered as an alternative therapy. The study includes increasing concentration essays of the nanoparticles and establishes, using the determination of turbidity by refractometry that could be a useful tool to inhibit bacterial growth, resulting successful. Nonetheless, further studies to identify the underlying action mechanisms of these nano-particles are going on in our group

Looking for new compounds to battle antibiotic resistance: optimization of organic solvents

A high number of pathogens have shown the capacity of resist to the action of antibiotics. This fact presents a very important problem to public health and highlights the necessity of looking for new substances as alternative to antibiotics. Since some of these substances have a hydrophobic nature they need to be solved in organic solvents. Some of these solvents are also toxic to bacteria, mainly affecting membranes. For these reasons it is necessary to perform a study of the toxicity of organic solvents to bacteria, which has been the aim of this work. Five organic solvents, DMF (dimethylformamide), TBME (tert-butyl methyl ether), THF (tetrahydrofuran), DMSO (dimethyl sulfoxide) and CH2Cl2 (dichloromethane), have been tested, using two of the most prevalent pathogens (Staphylococcus pseudintermedius and Pseudomonas aeruginosa,) both in animals and humans. The results show that, when possible, DMSO followed by TBME are the best options for testing new compounds in Staphylococcus pseudintermedius, whether DMF followed by TBME are the preferred solvents for testing hydrophobic compounds in Pseudomonas aeruginosa

Biofortificación de plantas de medicago sativa mediante el uso de nanoparticulas cargadas con hierro

El concepto de biofortificación se basa en incrementar el valor nutricional de los diferentes alimentos por medio de métodos de selección, mejora de cultivos o ingeniería genética. En este sentido, el trabajo que presentamos ha utilizado nanopartículas cargadas con hierro como parte de la disolución de riego, con el objeto de evaluar cómo se incorpora este elemento en plantas de cultivo destinadas a la alimentación animal. En este trabajo se empleó como planta experimental la especie Medicago sativa, cuyo nombre común es alfalfa y suele usarse como alimento de forrajeo para los animales de granja. Los experimentos mostraron que las nanopartículas tenían efectos muy positivos sobre el crecimiento y se observaba un aumento importante en la concentración de la clorofila de la propia planta

Assessing the Biofortification of Wheat Plants by Combining a Plant Growth-Promoting Rhizobacterium (PGPR) and Polymeric Fe-Nanoparticles: Allies or Enemies?

Biofortification has been widely used to increase mineral nutrients in staple foods, such as wheat (Triticum aestivum). In this study, a new approach has been used by analyzing the effect of inoculation with a plant growth-promoting rhizobacterium (PGPR), namely, Bacillus aryabhattai RSO25 and the addition of 1% (v/v) of organometallic Fe-containing polymeric nanoparticles (FeNPs) alone and in combination. Previously, the minimal inhibitory concentration of FeNPs for the bacterium was determined in order not to inhibit bacterial growth. All treatments had minor effects on seed germination and plant survival. Considering the physiology of plants, several photosynthetic parameters were significantly improved in individual treatments with FeNPs or the bacterium, particularly the efficiency of the photosystem II and the electron transport rate, which is indicative of a better photosynthetic performance. However, at the end of the experiment, a significant effect on final plant growth was not observed in shoots or in roots. When using FeNPs alone, earlier spike outgrow was observed and the final number of spikes increased by 20%. Concerning biofortification, FeNPs increased the concentration of Fe in spikes by 35%. In fact, the total amount of Fe per plant base rose to 215% with regard to the control. Besides, several side effects, such as increased Ca and decreased Na and Zn in spikes, were observed. Furthermore, the treatment with only bacteria decreased Na and Fe accumulation in grains, indicating its inconvenience. On its side, the combined treatment led to intermediate Fe accumulation in spikes, since an antagonist effect between RSO25 and FeNPs was observed. For this reason, the combined treatment was discouraged. In conclusion, of the three treatments tested, FeNPs alone is recommended for achieving efficient Fe biofortification in wheat.Ministry of Science and Innovation of Spain grant PID2019-109371GB-I00Junta de Andalucía (Spain) Project FQM-135University of Seville, Spain PPIT-2020/0000109

Culturomics and Circular Agronomy: Two Sides of the Same Coin for the Design of a Tailored Biofertilizer for the Semi-Halophyte Mesembryanthemum crystallinum

According to the EU, the global consumption of biomass, fossil fuels, metals, and minerals is expected to double by 2050, while waste will increase by 70%. In this context, the Circular Economy Action Plan (CEAP) intends to integrate development and sustainability. In this regard, tailored biofertilizers based on plant growth-promoting bacteria (PGPB) can improve plant yield with fewer inputs. In our project, an autochthonous halophyte of the Andalusian marshes, namely Mesembryanthemum crystallinum, was selected for its interest as a source of pharmaceuticals and nutraceuticals. The aim of this work was to use a culturomics approach for the isolation of specific PGPB and endophytes able to promote plant growth and, eventually, modulate the metabolome of the plant. For this purpose, a specific culture medium based on M. crystallinum biomass, called Mesem Agar (MA), was elaborated. Bacteria of three compartments (rhizosphere soil, root endophytes, and shoot endophytes) were isolated on standard tryptone soy agar (TSA) and MA in order to obtain two independent collections. A higher number of bacteria were isolated on TSA than in MA (47 vs. 37). All the bacteria were identified, and although some of them were isolated in both media (Pseudomonas, Bacillus, Priestia, Rosellomorea, etc.), either medium allowed the isolation of specific members of the M. crystallinum microbiome such as Leclercia, Curtobacterium, Pantoea, Lysinibacillus, Mesobacillus, Glutamicibacter, etc. Plant growth-promoting properties and extracellular degrading activities of all the strains were determined, and distinct patterns were found in both media. The three best bacteria of each collection were selected in order to produce two different consortia, whose effects on seed germination, root colonization, plant growth and physiology, and metabolomics were analyzed. Additionally, the results of the plant metabolome revealed a differential accumulation of several primary and secondary metabolites with pharmaceutical properties. Overall, the results demonstrated the feasibility of using “low cost media” based on plant biomass to carry out a culturomics approach in order to isolate the most suitable bacteria for biofertilizers. In this way, a circular model is established in which bacteria help plants to grow, and, in turn, a medium based on plant wastes supports bacterial growth at low prices, which is the reason why this approach can be considered within the model of “circular agronomy”.Junta de Andalucía - PAIDI_2020_00682Universidad de Sevilla - PPIT-2022-E

Antimicrobial and Antibiofilm Effect of 4,4′-Dihydroxy-azobenzene against Clinically Resistant Staphylococci

The spread of antibiotic resistance among human and animal pathogens is one of the more significant public health concerns. Moreover, the restrictions on the use of particular antibiotics can limit the options for the treatment of infections in veterinary clinical practice. In this context, searching for alternative antimicrobial substances is crucial nowadays. In this study, 4,4′-dihydroxy-azobenzene (DHAB) was tested for its potential in vitro as an antimicrobial agent against two relevant human and animal pathogens, namely Staphylococcus aureus and Staphylococcus pseudintermedius. The values of minimal inhibitory concentration (MIC) were 64 and 32 mg/L respectively, and they comparable to other azo compounds of probed antimicrobial activity. In addition, the minimal bactericidal concentrations (MCB) were 256 and 64 mg/L. The mechanism by which DHAB produces toxicity in staphylococci has been investigated. DHAB caused membrane damage as revealed by the increase in thiobarbituric acid reactive substances (TBARS) such as malondialdehyde. Furthermore, differential induction of the enzymes peroxidases and superoxide dismutase in S. aureus and S. pseudintermedius suggested their prevalent role in ROS-scavenging due to the oxidative burst induced by this compound in either species. In addition, this substance was able to inhibit the formation of biofilms by both bacteria as observed by colorimetric tests and scanning electron microscopy. In order to assess the relevance of DHAB against clinical strains of MRSA, 10 clinical isolates resistant to either methicillin or daptomycin were assayed; 80% of them gave values of CMI and CMB similar to those of the control S. aureus strain. Finally, cutaneous plasters containing a composite formed by an agar base supplemented with DHAB were designed. These plasters were able to inhibit in vitro the growth of S. aureus and S. pseudintermedius, particularly the later, and this suggests that this substance could be a promising candidate as an alternative to antibiotics in the treatment of animal skin infections, as it has been proven that the toxicity of this substance is very low particularly at a dermal level.Ministerio de Ciencia e Innovación PID2019-109371GB-I00Junta de Andalucía US-138087

Innovative compounds to battle multiresistence to antibiotics: use of PVA-Tannic acid nanoparticles to inibit staphylococcus pseudointermedius growth

Antibiotic resistance is an increasing public health problem that affects numerous pathogens, including Staphylococcus pseudintermedius, which has a high prevalence of methicillin resistance and can be easily transmitted to humans. Nowadays, the scientific community is developing new compounds that not only improve classic therapies in fighting antibiotic resistances but also prevent its appearance, essential to maintain health protection. The main objective of the present study is to synthesize tannic acid and polyvinyl alcohol nanoparticles and to determine their potential as growth inhibitors for S. pseudintermedius, to be considered a potential alternative therapy. The study includes diameter and Z-potential measurements for nanoparticles characterization and antimicrobial effect assays with different nanoparticles concentrations. MIC90 is determined as 112 μg/mL. Nonetheless, further studies to identify the underlying action mechanisms of these nanoparticles are going on in our group