Inhibitory Potential of Thymus vulgaris Essential Oil against Growth, Biofilm Formation, Swarming, and Swimming in Pseudomonas syringae Isolates

Abstract

As a follow-up to previous studies, the effects of Thymus vulgaris essential oil on selected virulence factors (growth, sessile cell survival, swimming, swarming, and exopolysaccharide production) were evaluated in phytopathogenic Pseudomonas syringae strains isolated from soybean fields in Argentina; reference strains Pseudomonas savastanoi pv. glycinea B076 and Pseudomonas aeruginosa PAO1. P. syringae are responsible for bacterial blight, a disease that affects crops worldwide. Plant bacterioses are usually treated with antibiotics and copper compounds, which may contribute to the development of resistance in pathogens and damage the environment. For these reasons, eco-friendly alternatives are necessary. Although aromatic plants are a natural source of antimicrobial substances, the effects of these substances on phytopathogenic bacteria remain largely unexplored. Subinhibitory concentrations of the oil significantly reduced the slope and rate of bacterial growth. In addition, biofilm and exopolysaccharide (EPS) production were inhibited, with swimming and swarming motility patterns being affected at all of the oil concentrations tested. Therefore, TEO could potentially be a highly efficient antipseudomonal agent for treating plant infections caused by P. syringae.

Effect of applications of oregano and thyme essential oils in Glycine max seeds against bacterial blight caused by Pseudomonas savastanoi

“…Even more, the inhibitory effect of these essential oils on P. syringae and some virulence factors (bio lm, toxins, etc.) was previously reported by this research group (Carezzano, et al 2023;Carezzano, et al 2017;Oliva et al, 2015).…”

“…Donmez et al (2022) reported variable effects of different Satureja species EO on bean seed germination, with certain EOs causing a slight decrease in germination rates. Additionally, Della Pepa et al (2019) found that some EOs exhibited antifungal and antibacterial activity but negatively impacted seed germination and radical elongation in lettuce, watercress, and tomato However, our studies yielded different results, indicating very low phytotoxicity in oregano and no phytotoxic effects in thyme when safe concentrations were employed.Earlier studies conducted by our research team, focusing on phytopathogenic P. syringae strains isolated from soybean plants, revealed that both essential oils (EOs) exhibited the ability to hinder growth and the synthesis of virulence factors, including phytotoxins and bio lms, even at subinhibitory concentrations(Carezzano et al, 2017;Sotelo et al, 2023;Carezzano et al, 2023) Building upon these ndings, in this study, both EOs were utilized at subinhibitory and non-phytotoxic concentrations to treat soybean seeds infected with the phytopathogen P. syringae in eld trials, aiming to potentially employ them as seed protectants in the future. Results from the in vivo trials demonstrated that the EO was effective in reducing disease and increasing crop yield.…”

Special Issue on “Secondary Metabolites: Extraction, Optimization, Identification and Applications in Food, Nutraceutical, and Pharmaceutical Industries”

“…The impact of Thymus vulgaris essential oil on virulence factors in Pseudomonas syringae strains, emphasizing growth, biofilm formation, exopolysaccharide synthesis, and motility patterns was discussed by Carezzano and colleagues [3]. The essential oil's sub-inhibitory concentrations notably impede bacterial growth rate and slope, while effectively inhibiting biofilm production and exopolysaccharide synthesis.…”