RESUMEN
Verticillium wilt of olive (VWO) caused by Verticillium dahliae is considered a major olive (Olea europaea) disease in Mediterranean-type climate regions. The lack of effective chemical products against VWO makes it necessary to search for alternatives such as biological control. The main goal of this study was to evaluate the effect of six Streptomyces spp. strains as biological control agents (BCAs) against VWO. All of them were molecularly characterized by sequencing 16S or 23S rRNA genes and via phylogenetic analysis. Their effect was evaluated in vitro on the mycelial growth of V. dahliae (isolates V004 and V323) and on microsclerotia (MS) viability using naturally infested soils. Bioassays in olive plants inoculated with V. dahliae were also conducted to evaluate their effect against disease progress. In all the experiments, the reference BCAs Fusarium oxysporum FO12 and Aureobasidium pullulans AP08 were included for comparative purposes. The six strains were identified as Streptomyces spp., and they were considered as potential new species. All the BCAs, including Streptomyces strains, showed a significant effect on mycelial growth inhibition for both V. dahliae isolates compared to the positive control, with FO12 being the most effective, followed by AP08, while the Streptomyces spp. strains showed an intermediate effect. All the BCAs tested also showed a significant effect on the inhibition of germination of V. dahliae MS compared to the untreated control, with FO12 being the most effective treatment. Irrigation treatments with Streptomyces strain CBQ-EBa-21 or FO12 were significantly more effective in reducing disease severity and disease progress in olive plants inoculated with V. dahliae compared to the remaining treatments. This study represents the first approach to elucidating the potential effect of Streptomyces strains against VWO.
RESUMEN
Macrophomina phaseolina and Rhizoctonia solani are considered two major soil-borne pathogens of Phaseolus vulgaris in Cuba. Their management is difficult, not only due to their intrinsic biology as soil-borne pathogens, but also because the lack of active ingredients available against these pathogens. Actinobacteria, a heterogeneous bacterial group traditionally known as actinomycetes have been reported as promising biological control agents (BCAs) in crop protection. Thus, the main objective of this study was to evaluate the effectiveness of 60 actinobacterial strains as BCAs against M. phaseolina and R. solani in vitro by dual culture assays. The most effective strains were characterized according to their cellulolytic, chitinolytic and proteolytic extracellular enzymatic activity, as well as by their morphological and biochemical characters in vitro. Forty and 25 out of the 60 actinobacteria strains inhibited the mycelial growth of M. phaseolina and R. solani, respectively, and 18 of them showed a common effect against both pathogens. Significant differences were observed on their enzymatic and biochemical activity. The morphological and biochemical characters allow us to identify all our strains as species belonging to the genus Streptomyces. Streptomyces strains CBQ-EA-2 and CBQ-B-8 showed the highest effectiveness in vitro. Finally, the effect of seed treatments by both strains was also evaluated against M. phaseolina and R. solani infections in P. vulgaris cv. Quivicán seedlings. Treatments combining the two Streptomyces strains (CBQ-EA-2 + CBQ-B-8) were able to reduce significantly the disease severity for both pathogen infections in comparison with the non-treated and inoculated control. Moreover, they showed similar effect than that observed for Trichoderma harzianum A-34 and with Celest® Top 312 FS (Syngenta®; Basilea, Switzerland) treatments, which were included for comparative purposes.
RESUMEN
This study assessed the intestinal microbiota of juveniles of the White shrimp Litopenaus vannamei, whose feed was enriched with three probiotic formulations: Streptomyces sp. RL8 (RL8); a mix of Lactobacillus graminis and Streptomyces spp. RL8 and N7 (Lac-Strep); and a mix of Bacillus spp. and Streptomyces spp. RL8 and N7 (Bac-Strep). The analysis was performed by sequencing the V3 region of the 16S rRNA gene of treated animals and the control group before and after Vibrio parahaemolyticus challenge. After challenge, the highest Shannon diversity indexes corresponded to RL8 and Bac-Strep (3.94 ± 0.11 and 3.39 ± 0.3, respectively) and the lowest to the control group (2.58 ± 0.26). The most abundant phyla before and after challenge were Proteobacteria, Actinobacteria, and Bacteroidetes. The principal component analysis and Statistical Analysis of Metagenomic Profiles (STAMP) showed that the gut microbiota of the groups RL8 and Bac-Strep after challenge was different from the other experimental groups, which was characterized by a higher bacterial diversity, as well as a significant stimulation of the Bacteriovorax population and other antimicrobial producing genera that protected shrimp from infection.
Asunto(s)
Microbioma Gastrointestinal , Penaeidae/microbiología , Streptomyces , Animales , Biodiversidad , Interacciones Microbianas , Probióticos , ARN Ribosómico 16S/genética , Vibrio parahaemolyticusRESUMEN
The TOpological MOlecular COMputer Design (TOMOCOMD-CARDD) approach has been introduced for the classification and design of antimicrobial agents using computer-aided molecular design. For this propose, atom, atom-type, and total quadratic indices have been generalized to codify chemical structure information. In this sense, stochastic quadratic indices have been introduced for the description of the molecular structure. These stochastic fingerprints are based on a simple model for the intramolecular movement of all valence-bond electrons. In this work, a complete data set containing 1006 antimicrobial agents is collected and presented. Two structure-based antibacterial activity classification models have been generated. The models (including nonstochastic and stochastic indices) classify correctly more than 90% of 1525 compounds in training sets. These models permit the correct classification of 92.28% and 89.31% of 505 compounds in an external test sets. The TOMOCOMD-CARDD approach, also, satisfactorily compares with respect to nine of the most useful models for antimicrobial selection reported to date. Finally, a virtual screening of 87 new compounds reported in the antiinfective field with antibacterial activities is developed showing the ability of the TOMOCOMD-CARDD models to identify new leads as antibacterial.
Asunto(s)
Antibacterianos/química , Modelos Teóricos , Relación Estructura-Actividad Cuantitativa , Antibacterianos/clasificación , Simulación por Computador , Bases de Datos Factuales , Conformación Molecular , Procesos EstocásticosRESUMEN
A novel approach to bio-macromolecular design from a linear algebra point of view is introduced. A protein's total (whole protein) and local (one or more amino acid) linear indices are a new set of bio-macromolecular descriptors of relevance to protein QSAR/QSPR studies. These amino-acid level biochemical descriptors are based on the calculation of linear maps on Rn[f k(xmi):Rn-->Rn] in canonical basis. These bio-macromolecular indices are calculated from the kth power of the macromolecular pseudograph alpha-carbon atom adjacency matrix. Total linear indices are linear functional on Rn. That is, the kth total linear indices are linear maps from Rn to the scalar R[f k(xm):Rn-->R]. Thus, the kth total linear indices are calculated by summing the amino-acid linear indices of all amino acids in the protein molecule. A study of the protein stability effects for a complete set of alanine substitutions in the Arc repressor illustrates this approach. A quantitative model that discriminates near wild-type stability alanine mutants from the reduced-stability ones in a training series was obtained. This model permitted the correct classification of 97.56% (40/41) and 91.67% (11/12) of proteins in the training and test set, respectively. It shows a high Matthews correlation coefficient (MCC=0.952) for the training set and an MCC=0.837 for the external prediction set. Additionally, canonical regression analysis corroborated the statistical quality of the classification model (Rcanc=0.824). This analysis was also used to compute biological stability canonical scores for each Arc alanine mutant. On the other hand, the linear piecewise regression model compared favorably with respect to the linear regression one on predicting the melting temperature (tm) of the Arc alanine mutants. The linear model explains almost 81% of the variance of the experimental tm (R=0.90 and s=4.29) and the LOO press statistics evidenced its predictive ability (q2=0.72 and scv=4.79). Moreover, the TOMOCOMD-CAMPS method produced a linear piecewise regression (R=0.97) between protein backbone descriptors and tm values for alanine mutants of the Arc repressor. A break-point value of 51.87 degrees C characterized two mutant clusters and coincided perfectly with the experimental scale. For this reason, we can use the linear discriminant analysis and piecewise models in combination to classify and predict the stability of the mutant Arc homodimers. These models also permitted the interpretation of the driving forces of such folding process, indicating that topologic/topographic protein backbone interactions control the stability profile of wild-type Arc and its alanine mutants.
Asunto(s)
Alanina/química , Biología Computacional/métodos , Modelos Teóricos , Proteínas/química , Relación Estructura-Actividad Cuantitativa , Proteínas Represoras/química , Proteínas Virales/química , Sustitución de Aminoácidos , Modelos Lineales , Mutación , Proteínas Represoras/genética , Programas Informáticos , Temperatura , Proteínas Virales/genética , Proteínas Reguladoras y Accesorias ViralesRESUMEN
Se realizó la induccion in vitro de resistencia al vinifurano 1-(5-Bromofor-2-il)-2-Bromo-2-Nitroeteno (G-1) mediante la técnica de concentraciones subinhibitorias en dos cepas de Candida albicans y Pseudomonas aeruginosa. Se obtuvo un aumento del valor de la CIM inicial para las Cepas de Candida albicans desde 2 hasta 16 ug/ml, mientras que en la cepas de Pseudomonas aeruginosa el valor de la CIMinicial se mantuvo invariable durante todo el ensayo. Conjunatmente se determinó la frecuencia de mutación espontánea en las dos cepas de referencia exponiendolas a múltiplos de CIM de la droga en ensayo igual a 2,4 y 8 veces este valor (AU)
Asunto(s)
Humanos , Mutación , Candida albicans , Pseudomonas aeruginosaRESUMEN
Se comparó el efecto psot antibiótico (EPA) del G-1 y la gentamicina frente a escherichia coli y staphylococcus aureus. El EPA fué inducido por exposición auna concentración de 4 x CIM de gentamicina. El G-1 produjo un EPA prlongado (>2h) en el rango de 0,8 a 3,6 h para la mayoría de las cepas ensayadas. En lascepas gram positivas estudiadas la gentamicina demostro un EPA ligeramente superior al G-1, minetras queen las cepas gram negativas fué menor. Se comparó conujuntamente, el EPA del G-1 a dos y cuatro veces elvalor de la CIM en las cepas de referencia. No hubo una correlación etadística entre la concentración y eol EPA para el G-1
Asunto(s)
Escherichia coli/efectos de los fármacos , Gentamicinas/clasificaciónRESUMEN
Se comparó el efecto psot antibiótico (EPA) del G-1 y la gentamicina frente a escherichia coli y staphylococcus aureus. El EPA fué inducido por exposición auna concentración de 4 x CIM de gentamicina. El G-1 produjo un EPA prlongado (>2h) en el rango de 0,8 a 3,6 h para la mayoría de las cepas ensayadas. En lascepas gram positivas estudiadas la gentamicina demostro un EPA ligeramente superior al G-1, minetras queen las cepas gram negativas fué menor. Se comparó conujuntamente, el EPA del G-1 a dos y cuatro veces elvalor de la CIM en las cepas de referencia. No hubo una correlación etadística entre la concentración y eol EPA para el G-1(AU)