Judul: Identifikasi dan Karakterisasi Fragmen DNA Genom yang Terlibat dalam Biosintesis Antifungi pada Bacillus sp
Abstrak: Bacillus merupakan salah satu genus bakteri yang dikenal sebagai penghasil antifungi. Empat isolat Bacillus asal tanah yaitu Cr 24, Cr 64, Cr 66, dan Cr 68 yang digunakan dalam penelitian ini memiliki karakter pemacu pertumbuhan tanaman dan mampu menghambat pertumbuhan fungi patogen Fusarium oxysporum dan/atau Rhizoctonia solani. Penelitian ini bertujuan untuk mengidentifikasi dan mengkarakterisasi gen penyandi antifungi zwittermicin A, bacilysocin, surfactin, dan iturin A pada Bacillus sp. dengan polymerase chain reaction (PCR). Primer yang digunakan telah dilaporkan sebelumnya dapat mengamplifikasi bagian gen-gen antifungi. Bagian gen resistensi antifungi zwittermicin A (zmaR) berukuran 951 pb dengan kandungan GC sebesar 34,78% berhasil diidentifikasi pada genom Cr 64. Fragmen genom Cr 64 tersebut memiliki homologi dengan gen zmaR (1128 pb) pada Bacillus cereus UW85 dengan tingkat kesamaan 98%. Gen zmaR merupakan bagian dari kelompok gen biosintesis zwittermicin A, sehingga diduga isolat Cr 64 berpotensi memiliki keseluruhan kelompok gen yang menyandikan antifungi zwittermicin A. Fragmen gen penyandi antifungi bacilysocin, surfactin, dan iturin A belum dapat diperoleh dari keempat isolat dengan pasangan primer yang digunakan dalam penelitian ini. Genom isolat Bacillus yang telah dilaporkan memiliki gen antifungi perlu digunakan sebagai kontrol untuk memastikan ketepatan kondisi PCR.
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Judul: Genetic Diversity of Antifungal-Producing Rhizobacteria of Bacillus sp. Based on Amplified rDNA Restriction Analysis (ARDRA) and 16S rRNA Sequence
Abstrak: Genus Bacillus has indirectly mechanism to induce the growth of soybean plant by growth suppression of pathogen through production of antibiotic. The objective of this research was to analyze the diversity of 22 antifungal-producing rhizobacteria of Bacillus sp. strain Cr isolated from rhizosphere of soybean plant based on 16S rRNA Sequence and Amplified rDNA Restriction Analysis (ARDRA). ARDRA was a tool to measure and analyze the diversity of 22 isolates through digestion of 16S rRNA gene by restriction enzymes i.e. HinfI, HaeIII, and RsaI. Based on this analysis, genetic diversity of 22 Bacillus Cr isolates were classified into eight different groups by ARDRA analysis. Moreover, six isolates selected randomly from each ARDRA group that have strong activity to suppress fungal growth were compared with reference strains based on 16S rRNA partial sequence. The distributions of 22 isolates were genetically diverse on several species of Bacillus sp. such as B. subtilis, B. cereus, and B. fusiformis. Therefore, ARDRA is a reliable technique to analyze genetic diversity of huge bacterial community.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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