Investigation of antibacterial and wound healing activities of the extract of Rhodotorula mucilaginosa endophyte isolated from cucumber leaves

Endophytic fungi represent a reservoir of pharmacologically essential secondary metabolites. The current study focused on the antibacterial properties of the endophytic yeast-like fungus Rhodotorula mucilaginosa (R. mucilaginosa) isolated for the first time from Cucumis sativus (cucumber) leaves. After isolation, R. mucilaginosa was identified by 18S rRNA gene sequencing and was cultured on Asian rice for production of fungal metabolites. Then, its phytochemical profile was elucidated using LC-HRESI-MS/MS technique to reveal 22 compounds which are mainly carotenoids and fatty acids in nature. Dried ethyl acetate extract of R. mucilaginosa was tested for antimicrobial activity against Pseudomonas aeruginosa isolates. The extract of R. mucilaginosa (ERM) showed minimum inhibitory concentrations with a range from 64 to 512 µg/mL. The crystal violet assay was utilized to determine the effect of ERM on the tested isolates' ability to produce biofilms. The percentage of strong biofilm-forming isolates dropped from 20 to 3.3% and 10%, respectively, after the treatment with ½ and ¼ MICs of ERM. When tested isolates of P. aeruginosa were exposed to sub-MICs of ERM, their cell size significantly decreased, and their biofilm matrix was reduced. The in vitro anti-inflammatory activity of ERM was supported by the marked decrease in TNF-α gene expression in the cells treated with either ERM or piroxicam compared to the control cells. The wound healing effect of ERM was investigated in vitro, where ERM showed improvement in the wound healing process. In addition, the wound healing effect of ERM was investigated in vivo using a model of infection in rats, where the wounds were infected with P. aeruginosa. The histological investigation of the wound showed a remarkable improvement in the group treated with ERM. Therefore, further investigation is required to explore the possible application of ERM as a potential antibacterial agent, which could aid in our fight against pathogenic microbes that have become resistant.