Endophytes associated with medicinal plants are a potential source of valuable natural products. This study aimed to evaluate the antibacterial and antibiofilm activities of endophytic bacteria from Archidendron pauciflorum against multidrug-resistant (MDR) strains. A total of 24 endophytic bacteria were isolated from the leaf, root, and stem of A. pauciflorum. Seven isolates showed antibacterial activity with different spectra against four MDR strains. Extracts derived from four selected isolates (1 mg/mL) also displayed antibacterial activity. Among four selected isolates, DJ4 and DJ9 isolates exhibited the strongest antibacterial activity against P. aeruginosa strain M18, as indicated by the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) (DJ4 and DJ9 MIC: 7.81 µg/mL; DJ4 and DJ9 MBC: 31.25 µg/mL). 2 × MIC of DJ4 and DJ9 extracts was found to be the most effective concentration to inhibit more than 52% of biofilm formation and eradicate more than 42% of established biofilm against all MDR strains. 16S rRNA-based identification revealed four selected isolates belong to the genus Bacillus. DJ9 isolate possessed nonribosomal peptide synthetase (NRPS) gene, and DJ4 isolate possessed NRPS and polyketide synthase type I (PKS I) gene. Both these genes are commonly responsible for secondary metabolites synthesis. Several antimicrobial compounds, including 1,4-dihydroxy-2-methyl-anthraquinone and paenilamicin A1, were detected in the bacterial extracts. This study highlights endophytic bacteria isolated from A. pauciflorum provide a great source of novel antibacterial compounds.
Keywords: Antibacterial; Antibiofilm; Bacillus; Endophytes; Nonribosomal peptide synthetase; Polyketide synthase.
© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.