Antibacterial Activity of Bacillus sp. HSFI Isolated from Holothuria scabra

Abstract

Staphylococcus aureus and Escherichia coli are important bacteria that cause various infectious
diseases. Clinically, the incidence of antibiotic resistance against these two bacteria needs serious
attention. Therefore, the search for new antibiotics is important. Microorganisms including bacteria
can be a source of discovery of new antibiotics. This study carried out the extraction of secondary
metabolites from nine Bacillus sp. HSFI isolated from intestinal fermented sea cucumber (Holothuria
scabra). Secondary metabolites of Bacillus sp. HSFI was produced using media with Starch, Yeast,
Peptone, and then extracted using ethyl acetate. As much 20 µg of extract of each Bacillus sp. HSFI was
tested for antibacterial activity using the disc diffusion method. The results showed that the ethyl acetate
extract of Bacillus sp. HSFI-2 and HSFI-9 can produce S. aureus growth inhibition zone with diameters
of 6.7 and 17.0 mm, respectively. Meanwhile, E. coli can be inhibited by ethyl acetate extracts of Bacillus
sp. HSFI-2, HSFI-4, HSFI-6, and HSFI-9 with inhibition zone diameters of 3.0; 2.0; 2.67, and 11.3 mm,
respectively. Ethyl acetate extract of Bacillus sp. HSFI-2 and HSFI-9 potential to be developed into
antibiotics because they have moderate to strong inhibitory activity against S. aureus and E. coli.

Keywords: Antibacterial agent; Bacillus sp.; drug resistance; Escherichia coli; Staphylococcus aureus