Antimicrobial activities of Plantactinospora sp. KBS50, a rare marine-derived actinomycete from the coastal area of Sarawak

Abstract

Aims: An actinomycete strain, designated KBS50, was isolated from a beach sediment sample collected from the Santubong area in Sarawak, Malaysia. This study reports on the identification, characterization and evaluation of the antimicrobial potential of this rare actinomycete. Methodology and results: KBS50 was identified as a potentially new species of Plantactinospora genus using the 16S rRNA gene sequence analysis. The rare actinomycete showed distinct morphological and physiological characteristics from other species of Plantactinospora. KBS50 exhibited strong antagonistic activities against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and fungi (Aspergillus niger, Ganoderma boninense, and Rhizoctonia solani). The actinomycete also tested positive for proteolytic activity. Meanwhile, secondary screening of the cell-free culture broths and the ethyl acetate crude extracts detected antimicrobial activity against the Gram-positive bacteria only. The minimum inhibitory concentration of the crude extract against B. subtilis and S. aureus was 5.21±1.30 µg/mL and 15.63±0.00 µg/mL, respectively. Conclusion, significance and impact of study: The results presented in this paper provided an insight into the capability of Plantactinospora sp. KBS50 as a potential source of bioactive secondary metabolites compounds. This study also showed that the marine-associated environment such as the coastal area in Sarawak can be a valuable source of unique actinomycetes that can be exploited for natural product discovery.

In vitro assessment of Bacillus subtilis FJ3 affirms its biocontrol and plant growth promoting potential

“…The experiment was run in triplicate. The formula for computing the susceptibility is (Juboi, 2017).…”