Effect of Growth Medium Composition on the Physicochemical Surface Properties of Pseudomonas savastanoi, the Agent of Olive Tuberculosis

Research into the formation of Pseudomonas savastanoi biofilms on olive trees is essential to prevent infections that induce tumour formation and damage tree health. To prevent the development of P. savastanoi biofilms, it is crucial to comprehend the factors influencing its adhesive behaviour. This research analysed the physicochemical properties of P. savastanoi in two types of media. P. savastanoi was cultivated in two media: nutrient agar (NA) and King B (KB), in solid and liquid forms. Wettability (θw), electron acceptor (γ+) electron donor (γ- ) properties, and surface free energy (ΔGiwi) are evaluated by contact angle measurements. The obtained results indicated that in solid media (NA and KB), P. savastanoi exhibited hydrophobic surface (𝜃WNA = 82.23°; 𝜃WKB= 94.9°), with strong electron donor (γNA− = 43.54 mJ.m-2; γKB− = 58.34 mJ·m-2) and mild electron acceptor (γNA+ = 0.32 mJ.m-2; γKB+ = 0.52 mJ·m-2) properties, along with negative surface free energy (ΔGiwiNA-76.13 mJ·m-2; ΔGiwiKB= -65.33 mJ·m-2. Conversely, in liquid media (NB and KB), the surface of P. savastanoi was generally hydrophilic (𝜃WNB= 55.43°; 𝜃WKB = 64.43°), with strong electron donor (γNB− = 29.23 mJ.m-2; γKB− = 41.38 mJ.m-2) and a surface free energy that registers as positive. Modification of the growth medium composition led to minor variations in P. savastanoi hydrophobicity and surface free energy. By understanding the factors involved in this adhesive behaviour, ecological methods to protect crops and contribute to more efficient environmental management and conservation of natural resources can be developed.