Judul: Screening of Antibiotic Resistant Antibacterial Activity and Identification of Soil Actinomycetes from Muna Island,  Southeast Sulawesi
Abstrak: Resistansi bakteri terhadap antibiotik merupakan salah satu masalah utama di bidang kesehatan. Eksplorasi aktinomiset tanah dari Pulau Muna, Sulawesi Tenggara diharapkan dapat menjadi alternatif baru penghasil senyawa antibakteri. Penelitian ini bertujuan mengevaluasi aktivitas antibakteri aktinomiset tanah asal Pulau Muna terhadap bakteri resistan antibiotik (multidrug-resistant bacteria) dan mengidentifikasi tiga isolat paling potensial berdasarkan gen 16S rRNA. Penapisan aktivitas antibakteri dari 25 isolat aktinomiset tanah dengan metode double layer agar menunjukkan 21 dari 25 (84%) isolat tersebut memiliki aktivitas antibakteri dengan spektrum yang bervariasi terhadap Escherichia coli strain M4, Klebsiella pneumoniae strain M19, Pseudomonas aeruginosa strain M19, Bacillus subtilis strain M18, dan methicillin-resistant Staphylococcus aureus. Ekstrak kasar dari tiga isolat aktinomiset yaitu kode APM7, APM11, dan APM21 diketahui memiliki spektrum antibakteri paling luas pada konsentrasi 80 mg mL−1. Ketiga ekstrak tersebut memiliki nilai minimum inhibitory concentration (MIC) berkisar antara 78 µg mL−1 hingga 10.000 µg mL−1 dan nilai minimum bactericidal concentration (MBC) berkisar lebih besar dari 156 µg mL−1 hingga lebih besar dari 10.000 µg mL−1. Berdasarkan karakteristik morfologi koloni dan selnya, ketiga isolat tergolong kelompok aktinomiset. Identifikasi menggunakan gen 16S rRNA menunjukkan bahwa ketiga isolat tersebut tergolong ke dalam kelompok Streptomyces spp. dengan nilai kemiripan lebih besar dari 98%., Exploration of soil actinomycetes from Muna Island, Southeast Sulawesi, is expected to be a new alternative source of antibacterial compounds. This study aimed to evaluate the antibacterial activity of the soil actinomycetes from Muna Island against multidrug-resistance bacteria and to identify the most potential isolates based on 16S rRNA gene. Preliminary screening of antibacterial activity of 25 isolates of soil actinomycetes through double layer agar assay showed that 21 out of 25 (84%) isolates had various antibacterial activities against Escherichia coli strain M4, Klebsiella pneumoniae strain M19, Pseudomonas aeruginosa strain M19, Bacillus subtilis strain M18, and methicillin-resistant Staphylococcus aureus. Interestingly, crude extracts derived from three actinomycetes, namely APM7, APM11, and APM21 have the broadest antibacterial spectrum, in each concentration of 80 mg mL−1. All three extracts have the minimum inhibitory concentration (MIC) values ranging from 78 µg mL−1 to 10.000 µg mL−1 and the minimum bactericidal concentration (MBC) values ranging from more than 156 μg/mL to more than 10.000 µg mL−1. Based on the cell and colony morphology, these three isolates belonged to actinomycetes group. In addition, identification using the 16S rRNA gene showed that the three isolates were closely related to Streptomyces spp. with high similarity (more than 98%).
Keyword: 16S rRNA, actinomycetes, antibacterial, multidrug-resistance bacteria, Streptomyces spp.

Judul: Aktivitas Antibakteri dari Bakteri Tanah Asal Pulau Muna, Sulawesi Tenggara terhadap Bakteri Resistan Antibiotik
Abstrak: Eksplorasi bakteri tanah penghasil senyawa antibakteri perlu dilakukan untuk mengatasi permasalahan resistansi bakteri patogen terhadap berbagai antibiotik. Tanah di Pulau Muna, Sulawesi Tenggara dianggap sebagai lingkungan yang menjanjikan untuk mengisolasi bakteri yang mampu menghasilkan senyawa antibakteri. Selain itu, riset terkait keragaman dan bioprospeksi bakteri asal pulau ini belum pernah dilaporkan. Penelitian ini bertujuan mengevaluasi aktivitas antibakteri bakteri tanah yang diisolasi dari Pulau Muna terhadap bakteri multidrug-resistant (MDR) dan mendeteksi potensi produksi senyawa bioaktifnya melalui deteksi gen. Pada penelitian sebelumnya, 15 isolat bakteri tanah telah berhasil diisolasi dari tanah Pulau Muna. Uji antagonis menunjukkan sebanyak 5 dari 15 isolat bakteri tanah memiliki spektrum aktivitas antibakteri yang berbeda terhadap lima strain bakteri target MDR. Berdasarkan uji cakram, ekstrak kasar dari dua isolat paling potensial, yaitu kode M7 dan P1, dapat menghambat pertumbuhan kelima bakteri target pada konsentrasi 80 mg/mL. Nilai minimum inhibitory concentration (MIC) dan minimum bactericidal concentration (MBC) kedua ekstrak berkisar antara 312,5–>10.000 μg/mL. Identifikasi berdasarkan sekuens gen 16S rRNA menunjukkan kekerabatan tertinggi (kemiripan >97%) isolat M7 dan P1 dengan Priestia (Bacillus) aryabhattai strain B8W22 dan Bacillus aerius strain 24K. Kedua isolat tersebut terdeteksi memiliki gen MlnA yang terlibat dalam biosintesis macrolactin. Bakteri tanah ini dapat diteliti lebih lanjut untuk dikembangkan sebagai sumber antibiotik baru., Exploration of soil bacteria producing antibacterial compounds is required to overcome the problem of pathogenic bacteria’s resistance to various antibiotics. The soil of Muna Island, Southeast Sulawesi, is considered a promising environment to isolate bacteria capable of producing antibacterial compounds. This study aimed to evaluate the antibacterial activity of soil bacteria isolated from Muna Island against multidrug-resistant (MDR) strains and to detect the potential production of bioactive compounds through gene detection. Antagonism assay showed that 5 out of 15 soil bacterial isolates exhibited various spectra of antibacterial activity against five MDR strains. According to the disc diffusion assay, the crude extracts derived from two most potential isolates, namely M7 and P1, inhibit the growth of the five MDR strains at a concentration of 80 mg/mL. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of both extracts ranged from 312,5 to >10.000 μg/mL. Based on the 16S rRNA sequences, M7 and P1 isolates were closely similar (similarity >97%) to Priestia (Bacillus) aryabhattai strain B8W22 and Bacillus aerius strain 24K, respectively. Both isolates were detected to have the MlnA gene which involved in the biosynthesis of macrolactin. These soil bacteria could be further studied and developed as a new source of antibiotics.
Keyword: 16S rRNA, antibacterial, MIC, multidrug-resistant bacteria, soil bacteria

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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