Judul: Identifikasi Molekuler Bakteri Pengurai Kitin Serangga dan Karakterisasi Enzim Kitinasenya
Abstrak: Rhizobacteria have beneficial effects for plant growth as phytostymulator, biofertilizer, and biocontrol agent. Our previous study showed that rhizobacteria of I.5, I.21, and II.14 isolates produced chitinases. The enzymes could degrade chitin of leaf miner (Aphis gossypi) and white fly (Bemisia tabaci). This research was conducted to identify the bacteria based on 16S r-RNA gene sequences and to characterize protein of chitinase from selected rhizobacteria. PCR amplification of 16S rRNA gene yielded DNA fragments of 1300 bp for each isolate. Based on sequences of the 16S rRNA gene, I.5 isolate was similar to Bacillus sp. with similarity percentage of 88% and I.21 and II.14 isolates were similar to B. cereus with similarity percentage of 93% and 91% respectively. Zymogram analyses showed that molecular weight of chitinase from I.21 isolate was 145 kDA and 168 kDa. However, no protein bands were showed in zymogram analyses of I.5 and II.14 isolates. Three chitinolytic bacteria have an opportunity to be used as natural biocontrols and bioinsecticides.
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Judul: Potensi Bakteri Kitinolitik untuk Menekan Penularan Cucumber mosaic virus strain soybean (CMV-S) melalui Aphis glycines Matsumura (Hemiptera: Aphididae) pada Kedelai
Abstrak: Bakteri kitinolitik merupakan salah satu agens hayati yang berpotensi untuk mengendalikan serangga vektor. Namun, keefektifannya perlu dievaluasi khususnya terhadap kemampuan vektor menularkan virus. Cucumber mosaic virus strain soybean (CMV-S) dan vektornya (Aphis glycines) merupakan salah satu faktor pembatas produksi kedelai di Indonesia. Penelitian ini bertujuan menguji keefektifan 3 isolat bakteri kitinolitik dalam menghambat kemampuan kutudaun menularkan CMV-S pada tanaman. Penelitian dilakukan dengan menggunakan rancangan acak lengkap (RAL) dengan 6 perlakuan, setiap perlakuan terdiri atas 15 tanaman dan diulang sebanyak 2 kali. Peubah yang diamati adalah waktu inkubasi, insidensi dan keparahan penyakit, tipe gejala, dan titer virus. Nilai indeks kitinolitik isolat NB-1, I-5 dan I-21 masing-masing adalah 2.956, 0.366, dan 0.418. Hasil penelitian menunjukkan bahwa tanaman perlakuan bakteri kitinolitik memperlihatkan parameter agronomi yang lebih baik. Secara umum, perlakuan bakteri kitinolitik mampu memperpanjang waktu inkubasi dan menurunkan titer virus; ketiga bakteri kitinolitik mampu menekan perkembangan virus pada tanaman. Tanaman perlakuan bakteri kitinolitik menunjukkan gejala yang lebih ringan dibandingkan tanaman kontrol dengan infeksi virus. Isolat I-21 dan NB-1 diduga memiliki sifat antivirus karena mampu menurunkan titer virus pada tanaman. Sedangkan isolat I-5 selain menekan titer virus pada tanaman, juga mampu menghambat kutudaun menularkan virus pada tanaman. Hal ini diduga I-5 memiliki sifat antifeedant yang menghambat kutudaun menularkan virus saat makan inokulasi.
Keyword: bakteri kitinolitik, kedelai, vektor, virus

Judul: : Persamaan Tunggal sebagai Representasi Kurva Komposit
Abstrak: A mathematical method is introduced to represent a composite curve based on an extension of analytic geometry. The representation is given either with a single equation or with two equations, in the case of parametric representation. This method permits the representation of composite curves in similar manner to the conventional representation of non-composite curves. Some mathematical tools, including Heaviside unit step function and periodizer function, are used in the establishment of a single equation. In this paper, regular equations of regular and irregular polygon, as well as composite curves of two dimensions, are implemented using a computer algebraic system, Mathematica.
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