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: Formulasi Hamilton Untuk Menggambarkan Deformasi Gelombang Soliter Dengan Dasar Tidak Rata Pada Fluida Dua Lapisan
Abstrak: Gelombang internal adalah suatu gelombang yang muncul di bawah permukaan laut sehingga gelombang ini tidak teramati secara kasat mata. Formulasi Hamilton dirumuskan untuk menjelaskan gerak gelombang ini. Dalam hal ini diasumsikan bahwa fluida yang ditinjau terdiri atas dua lapisan dengan masing-masing lapisan memiliki rapat massa yang konstan. Selain itu, diasumsikan pula fluida yang ditinjau berupa fluida tak mampat (incompressible) dan tak kental (invicid). Formulasi Hamilton dilakukan dengan meninjau fluida dua lapisan yang berada pada domain yang dibatasi oleh batas atas yang rata dan batas bawah yang tidak rata. Hamilton (energi total)-nya didefinisikan sebagai penjumlahan antara energi kinetik dan energi potensialnya. Karena energi kinetik tidak secara eksplisit dinyatakan dalam peubah fisis, maka digunakan metode asimtotik untuk menentukan energi totalnya. Dalam hal ini diasumsikan bahwa gelombang interfacial yang ditinjau cukup panjang, dan amplitudo yang cukup kecil. Persamaan Korteweg de- Vries (KdV) diperoleh, jika disumsikan bahwa gelombang interfacial hanya merambat pada satu arah, sedangkan jika gelombang tersebut merambat ke dua arah, diperoleh persamaan Boussinesq.
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