Secondary Metabolites of Pseudomonas aeruginosa LV Strain Decrease Asian Soybean Rust Severity in Experimentally Infected Plants.

Asian Soybean Rust (ASR), a disease caused by Phakopsora pachyrhizi, causing yield losses up to 90%. The control is based on the fungicides which may generate resistant fungi. The activation of the plant defense system, should help on ASR control. In this study, secondary metabolites of Pseudomonas aeruginosa LV strain were applied on spore germination and the expression of defense genes in infected soybean plants. The F4A fraction and the pure metabolites were used. In vitro, 10 µg mL-1 of F4A reduced spore germination by 54%, while 100 µg mL-1 completely inhibited. Overexpression of phenylalanine ammonia lyase (PAL), O-methyltransferase (OMT) and pathogenesis related protein-2 (PR-2; glucanases) defense-related genes were detected 24 and 72 h after soybean sprouts were sprayed with an organocopper antimicrobial compound (OAC). Under greenhouse conditions, the best control was observed in plants treated with 60 µg mL-1 of PCA, which reduced ASR severity and lesion frequency by 75% and 43%, respectively. Plants sprayed with 2 and 20 µg mL-1 of F4A also decreased severity (41%) and lesion frequency (32%). The significant reduction in spore germination ASR in plant suggested that the strain of these metabolites are effective against P. pachyrhizi, and they can be used for ASR control.

Whole-Genome Sequence of Bioactive Compound-Producing Pseudomonas aeruginosa Strain LV.

Pseudomonas aeruginosa is known for a high adaptive capacity due to the ability to synthesize several compounds that give advantages for competing with other microorganisms in the environment. The LV strain synthesizes bioactive compounds, mainly by secondary metabolism, with antitumor and antimicrobial activities against microbial pathogens.

Corrigendum: Determining the Targets of Fluopsin C Action on Gram-Negative and Gram-Positive Bacteria.

[This corrects the article DOI: 10.3389/fmicb.2020.01076.].

Determining the Targets of Fluopsin C Action on Gram-Negative and Gram-Positive Bacteria.

The antibiotic activity of metalloantibiotic compounds has been evaluated since the 90s, and many different modes of action were characterized. In the last decade, the effects of secondary metabolites produced by Pseudomonas aeruginosa LV strain, including a cupric compound identified as Fluopsin C, were tested against many pathogenic bacteria strains, proving their high antibiotic activity. In the present study, the bactericidal mechanisms of action of Fluopsin C and the semi-purified fraction F4A were elucidated. The results found in electron microscopy [scanning electron microscopy (SEM) and transmission electronic microscopy (TEM)] demonstrated that both Fluopsin C and F4A are affecting the cytoplasmatic membrane of Gram-positive and Gram-negative bacteria. These results were confirmed by fluorescence microscopy, where these bacteria presented permeabilization of their cytoplasmatic membranes after contact with the semi-purified fraction and pure compound. Using electronic and fluorescence microscopy, along with bacterial mutant strains with marked divisional septum, the membrane was defined as the primary target of Fluopsin C in the tested bacteria.