Judul: Detection of Biosynthetic Genes for Secondary Metabolites and Evaluation of Antibacterial Activity from Endophytic Bacteria Isolated from Syzygium cumini
Abstrak: Eksplorasi aktivitas antibakteri dari bakteri endofit yang berasosiasi dengan duwet (Syzygium cumini) perlu dilakukan untuk mengatasi kasus resistensi bakteri patogen terhadap antibiotik. Penelitian ini bertujuan mendeteksi keberadaan gen-gen biosintetik metabolit sekunder dan mengevaluasi aktivitas antibakteri dari bakteri endofit duwet. Berdasarkan teknik PCR, 9 dari 15 isolat bakteri endofit duwet (60%) membawa minimal satu gen biosintetik metabolit sekunder. Dual-culture assay menunjukkan bahwa empat dari 15 isolat bakteri endofit tanaman ini memiliki aktivitas antibakteri terhadap 2 atau 1 bakteri target Staphylococcus aureus ATCC 6538 dan Bacillus subtilis ATCC 19659. Isolat B2 dan D1 merupakan 2 isolat dengan aktivitas antibakteri terbaik. Secara konsisten, ekstrak kasar kedua isolat tersebut juga dapat menghambat S. aureus ATCC 6538 dan B. subtilis ATCC 19659 dengan zona hambat berkisar antara 8–12,33 mm. Nilai minimum inhibitory concentration (MIC) dan minimum bactericidal concentration (MBC) telah ditentukan menggunakan teknik microbroth-dilution. Nilai MIC ekstrak kasar kedua isolat lebih aktif terhadap B. subtilis ATCC 19659, dibandingkan dengan S. aureus ATCC 6538. Kedua ekstrak tersebut memiliki nilai MBC yang lebih tinggi dibanding nilai MIC-nya. Analisis Liquid Chromatography Quadrupole-tandem Mass Spectrometry (LC-MS/MS) menunjukkan bahwa ekstrak bakteri endofit duwet mengandung beberapa senyawa antibakteri, seperti cyclo(tyrosyl-propyl) dan cyclo(prolylvalyl)., Exploration of antibacterial activity from endophytic bacteria associated with Syzygium cumini is necessary to provide new sources of antibiotics to overcome resistance in pathogenic bacteria. This study aimed to detect the presence of antibiotic-biosynthetic genes and evaluate the antibacterial activity of endophytic bacteria isolated from S. cumini. Based on PCR screening, 9 out of 15 isolates (60%) carried at least one antibiotic-biosynthetic gene. Furthermore, the dual-culture assay showed that four out of 15 isolates showed remarkable antibacterial activity against either one or both target bacteria, including Staphylococcus aureus ATCC6538 and Bacillus subtilis ATCC19659. Endophytic bacteria coded as B2 and D1 exhibited the most promising antibacterial activity against both strains. Consistently, crude extracts of these isolates could inhibit the growth of B. subtilis ATCC19659 and S. aureus ATCC6538, with inhibition zone diameters ranging from 8 to 12.33 mm. According to microbroth-dilution assay, the minimum inhibitory concentration (MIC) values of these isolates were more active against B. subtilis ATCC19659 compared to S. aureus ATCC6538. Both extracts had minimum bactericidal concentration (MBC) higher than their MIC values. Liquid chromatography quadrupole-tandem mass spectrometry (LC-MS/MS) analysis showed the crude extracts derived from these isolates contained several antimicrobial compounds, such as cyclo (tyrosyl-propyl) and cyclo (prolylvalyl).
Keyword: antibacterial, Bacillus subtilis, biosynthetic genes, Staphylococcus aureus, Syzygium cumini