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: Karakterisasi Morfologi Sel dan Penapisan Aktivitas Hidrolisis dari Isolat Bakteri Tanah Pulau Muna, Sulawesi Tenggara
Abstrak: Bakteri penghasil enzim ekstraselular, khususnya enzim amilase, selulase, dan protease, dapat digunakan dalam berbagai industri. Lima belas isolat bakteri tanah yang diisolasi dari Pulau Muna, Sulawesi Tenggara, belum diketahui potensinya sebagai penghasil enzim-enzim tersebut. Penelitian ini bertujuan mengkarakterisasi morfologi sel dan menapis aktivitas amilolitik, proteolitik dan selulolitik dari bakteri tanah yang diisolasi dari Pulau Muna. Karakterisasi morfologi dilakukan dengan pewarnaan Gram. Penapisan bakteri dilakukan dengan metode kualitatif pada medium padat. Berdasarkan pengecatan Gram, 5 Isolat tergolong ke dalam bakteri Gram negatif dan 10 Isolat tergolong bakteri Gram positif, dengan bentuk sel yang bervariasi yaitu batang panjang dan bulat. Empat dari 15 isolat memiliki karakter hemolisis negatif atau gamma hemolisis sehingga diduga tidak bersifat patogen. Empat isolat tersebut selanjutnya digunakan untuk penapisan aktivitas hidrolisis terhadap amilum, selulosa, dan protein. Isolat M7 dan P7 mampu menghasilkan protease, selulase, dan amilase, sedangkan 2 isolat lainnya yaitu M4 dan P5 hanya mampu menghasilkan protease. Keempat bakteri tersebut dapat diteliti dan dikembangkan lebih lanjut sebagai penghasil enzim amilase, protease dan selulase., Bacteria producing extracellular enzymes, especially amylase, cellulase and protease enzymes, can be used in various industries. Fifteen isolates of soil bacteria isolated from Muna Island, Southeast Sulawesi, have no known potential as producers of these enzymes. This research aims to characterize cell morphology and screen the amylolytic, proteolytic and cellulolytic activities of soil bacteria isolated from Muna Island. Morphological characterization was carried out using Gram staining. Bacterial screening was carried out using qualitative methods on solid medium. Based on Gram staining, 5 isolates were classified as Gram negative bacteria and 10 isolates were classified as Gram positive bacteria, with varying cell shapes, namely long rods and round. Four of the 15 isolates had negative hemolysis or gamma hemolysis characteristics so they were suspected not to be pathogenic. The four isolates were then used to screen for hydrolysis activity on starch, cellulose and protein. Isolates M7 and P7 were able to produce protease, cellulase and amylase, while the other 2 isolates, namely M4 and P5, were only able to produce protease. These four bacteria can be researched and developed further as producers of amylase, protease and cellulase enzymes
Keyword: Amilase, hemolisis, indeks hidrolitik, Protease, Selulase

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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