Judul: Antibacterial Activity and Identification of Endophytic Bacteria Isolated from Ziziphus sp.
Abstrak: Penyakit infeksi yang disebabkan oleh bakteri patogen resistan antibiotik menjadi permasalahan utama kesehatan global. Bakteri endofit bidara (Ziziphus sp.) dapat menjadi sumber alternatif penghasil antibiotik baru. Penelitian ini bertujuan menganalisis aktivitas antibakteri isolat bakteri endofit bidara, mengidentifikasi isolat potensial melalui pendekatan molekuler, dan mengidentifikasi profil kimia dari isolat-isolat potensial. Sebanyak 21 isolat bakteri endofit telah berhasil diisolasi dari akar, batang, dan daun bidara. Dual-Culture Agar Diffusion Assay menunjukkan dua dari 21 isolat bakteri memiliki aktivitas antibakteri terhadap empat bakteri target. Estrak kasar metabolit sekunder kedua isolat potensial (80 mg/ml) mampu menghambat semua bakteri target dengan diameter zona hambat berkisar 8,3–15,0 mm. Nilai minimum inhibitory concentration (MIC) dan minimum bactericidal concentration (MBC) yang ditentukan dengan teknik microdilution menunjukkan bahwa kedua ekstrak tersebut memiliki nilai MIC berkisar antara 468,75–>30.000 µg/ml, dan MBC berkisar antara 468,75–>30.000 µg/ml. Berdasarkan analisis gen 16S rRNA, dua isolat potensial yaitu BBSB3 dan BDSB4 masing-masing memiliki kemiripan sekuens tertinggi dengan Pseudomonas aeruginosa strain DSM 50071 dan Pseudomonas aeruginosa strain N. Kedua isolat tersebut terdeteksi memiliki gen polyketide synthase I (PKS I) yang umumnya terlibat dalam biosintesis senyawa poliketida. Analisis liquid chromatograohy tandem mass spectrometry (LC-MS/MS) kedua ekstrak kasar menunjukkan keduanya memiliki berbagai senyawa aktif antibakteri., Infectious diseases caused by antibiotic-resistant pathogenic bacteria are one of the significant health problems worldwide. Exploring the antibacterial activity of endophytic bacteria associated with Ziziphus sp. may provide an alternative source of new antibiotics. This study aims to evaluate the antibacterial activity of endophytic bacteria isolated from Ziziphus sp., identify potential isolates through molecular approaches, and identify the chemical profiles of potential isolates. In previous research, 21 endophytic bacterial isolates were successfully isolated from Ziziphus sp. Antagonism assay showed that two of the 21 bacterial isolates had antibacterial activity against four target bacteria. At a concentration of 80 mg/ml, the crude extract of secondary metabolites of the two potential isolates could inhibit all target bacteria with inhibition zone diameters ranging from 8.3-15.0 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of both extracts ranged from 468.75–>30,000 µg/ml. Based on their 16S rRNA sequences, the selected isolates were closely similar to Pseudomonas aeruginosa strain DSM 50071, and Pseudomonas aeruginosa strain N. Both isolates were also detected to have the PKS I gene, which is generally involved in the biosynthesis of polyketide compounds. LC-MS/MS analysis of the two crude extracts showed both to have various antibacterial active compounds.
Keyword: 16S rRNA, LC-MS/MS, MIC, Pseudomonas aeruginosa, Gen PKS I