One of the most important postharvest plant pathogens that affect strawberries, grapes and tomatoes is Botrytis cinerea, known as gray mold. The fungus remains in latent form until spore germination conditions are good, making infection control difficult, causing great losses in the whole production chain. This study aimed to purify and identify phenazine-1-carboxylic acid (PCA) produced by the Pseudomonas aeruginosa LV strain and to determine its antifungal activity against B. cinerea. The compounds produced were extracted with dichloromethane and passed through a chromatographic process. The purity level of PCA was determined by reversed-phase high-performance liquid chromatography semi-preparative. The structure of PCA was confirmed by nuclear magnetic resonance and electrospray ionization mass spectrometry. Antifungal activity was determined by the dry paper disk and minimum inhibitory concentration (MIC) methods and identified by scanning electron microscopy and confocal microscopy. The results showed that PCA inhibited mycelial growth, where MIC was 25 μg mL-1. Microscopic analysis revealed a reduction in exopolysaccharide (EPS) formation, showing distorted and damaged hyphae of B. cinerea. The results suggested that PCA has a high potential in the control of B. cinerea and inhibition of EPS (important virulence factor). This natural compound is a potential alternative to postharvest control of gray mold disease.
Multidrug-resistant organisms (MDRO) are a great problem in hospitals, where thousands of people are infected daily, with the occurrence of high mortality rates, especially in infections caused by Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-producing Kpn). The challenge is to find new compounds that can control KPC producing-Kpn infections. The aim of this study was to evaluate the antibiotic activity of the F3d fraction produced by the Pseudomonas aeruginosa LV strain against clinical isolates of KPC-producing Kpn. The results showed that the minimum inhibitory concentration of F3d (62.5 µg mL(-1)), containing an organic metallic compound, killed planktonic cells of KPC-producing Kpn strains after 30 min of incubation. At the same concentration, this fraction also showed an inhibitory effect against biofilm of these bacteria after 24 h of incubation. Treatment with the F3d fraction caused pronounced morphological alterations in both planktonic and biofilm cells of the bacteria. The inhibitory effect of the F3d fraction seems to be more selective for the bacteria than the host cells, indicating its potential in the development of new drugs for the treatment of infections caused by KPC-producing Kpn and other MDRO.
This study investigated the protective effects of secondary bacterial metabolites, produced by Pseudomonas sp. (bacterium strain LN), on citrus canker disease caused by Xanthomonas axonopodis pv. citri (Xac 306). The LN bacteria strain was cultured in liquid medium and the supernatant free-cells was treated with methanol (AMF) and ethyl acetate (AEF), respectively, and then the extract was concentrated, filtrated, lyophilized and fractionated by vacuum liquid chromatography (VLC). After VLC, eight fractions were obtained. All fractions' activity against Xac 306 by agar well diffusion assay and minimum inhibitory concentration but in different concentrations were tested. Cytotoxicity effects were observed in all fractions in 50 µg•mL −1 concentration. The comet assay demonstrated that the fractions EAF, VLC2 and VLC3 presented no genotoxic effects at tested concentrations. In plants only VLC3 showed significant results (p < 0.05), reducing the incidence of citrus canker lesions.
Microbial activity in the rhizosphere is essential for nutrient cycling, which can contribute to soil fertility and plant growth. This work aimed to evaluate the effects of two biological control agents (Trichoderma sp. and Beauveria sp.) on the functional groups of microorganisms in the soybean (Glycine max) rhizosphere and plant growth. The experiment was carried out in a greenhouse, and five replicates with one plant per pot (1000 mL), containing a mixture of soil: sand (4:1), were harvested and microbial communities evaluated at 7, 21, 45 and 60 days after soybean germination. The populations of heterotrophic bactéria (HBP), saprophytic fungi (SFP), fluorescent pseudomonads (PFP) and the functional groups of microorganisms related to carbon cycling [proteolytics (PP), amylolytics (AP) and cellulolytics (CP)], nitrogen cycling [dry weight of nodules (DWM)], and phosphorus cycling [AM fungi colonization (AM)] were estimated. A soil sample (1 g) was taken from the homogenized rhizosphere soil to estimate the culturable microbial community size. Samples were suspended in 9 mL of sterile saline (0.85%) and aliquots (50 ?L) of ten-fold dilutions spread on the respective culture medium. Plates were incubated at 28 °C and CFU were counted. The results showed that biological controls agents such as Trichoderma sp. and Beauveria sp. presented diferente effects on microbial community and Rhizophagus clarus colonization. Trichoderma sp. had positive influence on plant growth and soil microbial community, except for AM fungi. However, Beauveria sp. showed no significant differences in all evaluations, including plant growth.
Utilização de compostos naturais extraídos de Pseudomonas aeruginosa no incremento da produtividade do milho (Zea mays L.) e da soja (Glycine max L.
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