In vitro antimicrobial activity of the crude extract of the endophytic bacterium Pseudomonas aeruginosa (SS93) isolated from Sapindus saponaria L.

Abstract

Endophytes colonize the interior of plant tissues without causing any damage to their hosts. The plant Sapindus saponaria L., popularly known as ‘sabão-de-soldado’, presents a diversified endophytic microbiota and also medicinal properties. Endophytic microorganisms may produce secondary metabolites with different biotechnological properties. The present study aimed to evaluate the in vitro antibacterial and antifungal capacity of the crude extract of secondary metabolites produced by the endophytic bacteria P. aeruginosa SS93 isolated from S. saponaria leaves. The metabolites extract was obtained using the organic solvent ethyl acetate, and the antimicrobial activities were tested against six pathogenic bacteria (Enterococcus faecalis [ATCC 29212], Pseudomonas aeruginosa [ATCC 27853], Shigella flexneri [ATCC 12022], Salmonella enterica [CCCD a016], Escherichia coli [ATCC 25922], and Staphylococcus aureus [ATCC 25923]), and pathogenic fungi (Fusarium oxysporum, Glomerella sp., Sphaceloma sp., Fusarium solani, Maniliophtora perniciosa, and Sclerotinia sclerotiorum), by agar diffusion method. In the antibacterial assay, the best results were obtained against E. faecalis and S. aureus, where the formation of inhibition halos was observed in all tested concentrations, especially at 500 and 700 µg mL^-1. Positive inhibitory activity against phytopathogenic fungi was observed, with the highest inhibition recorded against F. oxysporum (61.1%), followed by Sphaceloma sp. (55.7%), M. perniciosa (35.6%), F. solani (34.4%), and Glomerella sp. (30.4%).