Judul: Physiological Characterization and Molecular Identification of Bacteriocin Producer Bacillus spp Isolated from Cangkuang Forest.
Abstrak: Bacillus spp from Cangkuang’s forest (A21, F13, and G3 isolates) were able to inhibit the growth of Xanthomonas oryzae pv. oryzae, Escherichia coli, and Staphylococcus aureus. Determination of inhibition activity, physiologycal, and sequences of 16S rRNA gene were conducted in this research. A21 isolate had the biggest inhibition index against S. Aureus and E. coli. G3 isolate had the biggest inhibition index against X. oryzae pv. oryzae. All Bacillus isolates showed a positive reaction for nitrates (exept F13), starch, gelatine, glucose, and O-nitrophenyl-β- D-galactopyranoside. 16S rRNA sequences of A21 and G3 isolates showed 94-95% similarity to Bacillus cereus, while F13 isolate had 96% similarity to Bacillus subtilis. Phylogenetic tree showed that all isolates were placed in the same group.
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Judul: Antimicrobial Activity of Bacillus sp. to Xanthomonas oryzae pv. oryzae, Pseudomonas syringae pv. glycines, and Pseudomonas fluorescens.
Abstrak: Leaf blight disease caused by bacterial plant pathogen such as X. oryzae pv. oryzae and P. syringae pv. glycines had deathly effect to plants. The pathogens can be controlled by biological control using P. fluorescens or antimicrobial substances. The research studied the inhibition ability and production of antimicrobial substances produced by Bacillus sp. againts bacterial plant pathogen such as X. oryzae pv. oryzae, P. syringae pv. glycines, and biological control P. fluorescens. As many as 31 Bacillus sp. isolates isolated from forest soil was determined their antimicrobial activity against indicator bacteria using double layer method. The result showed that 13 isolates was able to inhibit Staphylococcus aureus, Eschericia coli, and X. oryzae pv. oryzae growth, 8 isolates could inhibit P. fluorescens A growth, 9 isolates could inhibit P. fluorescens B growth, and 8 isolates could inhibit P. syringae pv. glycines growth. Bacillus sp. F13 had the fastest inhibition and good efficiency against all indicator bacteria. Mixed culture competition test showed that this isolate had a broad spectrum inhibition activity, it was able to inhibit Gram positive and Gram negative bacteria. The isolate could inhibit growth of P. syringae pv. glycines and X. oryzae pv. oryzae up to 100%. The antimicrobial substance the isolate was produced in the late logarithmic growth phase.
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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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