Bioactive Organocopper Compound from Pseudomonas aeruginosa Inhibits the Growth of Xanthomonas citri subsp. citri

Abstract

Citrus canker is a very destructive disease of citrus species. The challenge is to find new compounds that show strong antibiotic activity and low toxicity to plants and the environment. The objectives of the present study were (1) to extract, purify and evaluate the secondary metabolites with antibiotic activity produced by Pseudomonas aeruginosa LV strain in vitro against Xanthomonas citri subsp. citri (strain 306), (2) to determine the potential of semi-purified secondary metabolites in foliar application to control citrus canker under greenhouse conditions, and (3) to identify antibiotic activity in orange leaf mesophyll infected with strain 306, by electron microscopy. Two pure bioactive compounds were isolated, an organocopper antibiotic compound (OAC) and phenazine-1-carboxamide. Phenazine-1-carboxamide did not show any antibiotic activity under the experimental conditions used in this study. The OAC showed a high level of antibiotic activity with a minimum inhibitory concentration of 0.12 μg mL-1. In greenhouse tests for control of citrus canker in orange trees, the semi-purified fraction F3d reduced lesion formation by about 97%. The concentration used was 500 times lower than that for the recommended commercial copper-based product. Electron microscopy showed that F3d altered the exopolysaccharide matrix and caused cell lysis of the pathogen inside the citrus canker lesions. These results suggest that secondary metabolites produced by inducing P. aeruginosa LV strain have a high potential to be used as a bioproduct to control citrus canker.

Promising antifungal activity of new oxadiazole against Candida krusei

“…Scanning electron microscopy (SEM) was performed based on the protocol described by Oliveira [34]. C. krusei ATCC 6258 (2-3×10 3 cells/mL in RPMI-1640 medium) was exposed to LMM11 at the concentrations of 16 μg/mL, 32 μg/mL, 64 μg/mL and incubated in 24-well plates at 35˚C for 24 h. The cells were harvested, washed twice with PBS and fixed by immersion in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1 M sodium cacodylate buffer.…”

Soil Bacteria Isolated From Tunisian Arid Areas Show Promising Antimicrobial Activities Against Gram-Negatives

“…Many pharmaceutically important antibiotics have been identified in the past from this bioresource, e.g., vancomycin produced by Streptomyces orientalis isolated from a soil sample from Borneo ( Griffith, 1981 ), kanamycin produced by a soil bacterium Streptomyces kanamyceticus ( Umezawa et al, 1957 ), and erythromycin first isolated in 1952 from the soil bacterium Saccharopolyspora erythraea ( Staunton and Wilkinson, 1997 ). Bacterial genera reported so far as a bioresource with a high chance to detect compounds of interest are Actinomycetes ( Hotam et al, 2013 ; Tiwari and Gupta, 2013 ), Bacilli ( Sumi et al, 2015 ), and Pseudomonads ( Mukherjee et al, 2014 ; de Oliveira et al, 2016 ). In the present project so far unexplored arid sampling sites of Southern Tunisia were investigated, since the arid environment results in high competition between organisms.…”

New Insights about Antibiotic Production by Pseudomonas aeruginosa: A Gene Expression Analysis

“…The cells were recovered by centrifugation in a Jouan CR3 equipment (9,000 rpm/20 min, 4°C), resuspended in TRIZOL (INVITROGEN) and kept at −80°C. The confirmation of the antibiotic activity of the supernatants was confirmed as described elsewhere (De Oliveira et al, 2016 ). Both cultures were performed in biological triplicate (three samples for each condition, corresponding to three experiments separated spatially and temporally).…”

“…Additionally, the same strain produced a Phenazine-1-Carboxylic Acid (even if in low quantity) which shown antifungal potential against Botrytis cinerea (Simionato et al, 2017 ). Apparently, the copper chloride induces the production of this compounds, since no antimicrobial activity can be detected in the supernatant of P. aeruginosa strain LV cultured in its absence (De Oliveira et al, 2016 ).…”