Judul: Kloning fragmen DNA genom yang terlibat dalam toleransi asam-alumunium pada Bradyrhizobium japonicum melalui mutagenesis dengan transposon
Abstrak: Bakteri bintil akar Bradyrhizobium japonicum sensitif asam-aluminium telah berhasil dikonstruksi melalui metode mutagenesis dengan transposon untuk mengetahui gen yang terlibat dalam toleransi asam-aluminium pada B. japonicum. pUTmini-Tn5Km1 yang dibawa oleh Escherichia coli S17-1 (? pir) di transfer ke dalam sel B. japonicum toleran asam-Al melalui konjugasi dengan tiga waktu inkubasi mating yang berbeda. Mutan BJ 11 (25) diketahui tidak mampu tumbuh pada media Ayanaba (pH 4.5) yang ditambahkan 50 mM aluminium . Fragmen DNA sebesar 0.8 kb berhasil diisolasi dari genom BJ 11 (25) menggunakan teknik inverse polymerase chain reaction (Inverse PCR). Fragmen DNA tersebut kemudian diklon ke dalam plasmid pGEMT-Easy (~3 kb) menghasilkan plasmid rekombinan yang didesain sebagai pGEMT- 11 (~3.8kb).
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Judul: Analysis of genomic dna fragment involved in acid- aluminium tolerance in bradyrhizobium japonicum
Abstrak: Bradyrhizobium japonicum is one of Rhizobia species which generally form root nodule on soybean plant (Glycine max). In association with leguminous plant, root nodule bacteria (RNB) fix atmospheric nitrogen (N2) into NH3 which can be used for plant growth. Soil acidity is a significant problem affecting agricultural production in many areas of the world. Lowering pH of the soil can affect soil organisms including the microflora. Among the biological system affected by the decrease in soil pH are those between RNB and leguminous plants. It could affect the association result between them in fixing nitrogen. In the previous work, screening indigenous B. japonicum strains which tolerant to acid-aluminium has been reported. The potential strains were strains BJ11, BJ38, and KDR15. These tolerant strains could become a source of genetic material exploration which involved in acid-Al tolerance in B. japonicum. Transposon delivery was carried out through conjugation between Escherichia coli S17-1 (λ pir) carrying pUTmini-Tn5Km1 and acid-Al tolerant B. japonicum at 1:1 ratio. Frequency of transconjugation was in the range of 10-8–10-6 cells per recipients. A mutant AAS11.2 did not able to grow on the Ayanaba medium (pH 4.5) supplemented with 50 μM aluminium. AAS11.2 was able to form root nodule on siratro plant indicating that the gene involved in acid-Al tolerance was not related with nodulation. A 0.8 kb of the genomic DNA fragment flanking transposon involved in acid-Al tolerance was successfully isolated by inverse polymerase chain reaction (inverse PCR) from AAS11.2 genome. This fragment was subsequently cloned into pGEM-T Easy (∼3 kb) to yield a recombinant plasmid, designated as pGEMT-11 (∼3.8 kb), and sequenced. DNA sequenced analysis revealed that the genomic DNA fragment sequence had high homology with yhfK gene encoding putative inner membrane protein from Salmonella typhimurium (79% identity and 84% similarity, E-value= 1.0xe-100) which function as efflux transporter.
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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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