Judul: Antibacterial Activity of Endophytic Actinobacteria Isolated from Ziziphus sp. against Multidrug-Resistant Strains and Their Identification
Abstrak: Eksplorasi aktivitas antibakteri dari aktinobakteri endofit asal bidara (Ziziphus sp.) perlu dilakukan untuk mendapatkan sumber alternatif baru penghasil antibiotik. Penelitian ini bertujuan mengevaluasi aktivitas antibakteri pada aktinobakteri endofit bidara terhadap lima bakteri multidrug- resistant dan mengidentifikasi isolat potensial melalui pendekatan molekuler berdasarkan gen 16S rRNA. Pada penelitian sebelumnya, 30 isolat aktinobakteri telah berhasil diisolasi dari dari akar, batang, dan daun bidara. Penapisan melalui metode double layer agar diffusion menunjukkan bahwa lima dari 30 isolat aktinobakteri (16%) memiliki aktivitas antibakteri spesifik terhadap methicillin-resistant Staphylococcus aureus (MRSA) dan Bacillus subtilis strain M18. Ekstrak kasar metabolit sekunder dari empat isolat terpilih (BBK 1, DBK 2, DBK 3, dan DBSB 1) juga secara konsisten menujukkan aktivitas penghambatannya terhadap MRSA dengan diamter zona hambat berkisar antara 8±0,8–11±2,9 mm. Minimum inhibitory concentration (MIC) yang ditentukan berdasarkan teknik microbroth-dilution menunjukkan bahwa keempat ekstrak tersebut memiliki MIC yang berkisar 2.500–5.000 μg/mL. Karakterisasi morfologi koloni dan sel pada keempat isolat tersebut menujukkan bahwa isolat-isolat tersebut tergolong aktinobakteri. Berdasarkan identifikasi sekuens gen 16S rRNA, keempat isolat termasuk pada kelompok Streptomyces spp. dengan nilai kemiripan > 99%. Keempat isolat terpilih dapat diteliti dan dikembangkan lebih lanjut sebagai penghasil senyawa anti-MRSA di masa depan.
Keyword: Aktinobakteri endofit, antibakteri, methicillin⎯resistant Staphylococcus aureus (MRSA), Streptomyces spp., Ziziphus sp.

Judul: Antibacterial Activity and Identification of Endophytic Bacteria Isolated from Ziziphus sp.
Abstrak: Penyakit infeksi yang disebabkan oleh bakteri patogen resistan antibiotik menjadi permasalahan utama kesehatan global. Bakteri endofit bidara (Ziziphus sp.) dapat menjadi sumber alternatif penghasil antibiotik baru. Penelitian ini bertujuan menganalisis aktivitas antibakteri isolat bakteri endofit bidara, mengidentifikasi isolat potensial melalui pendekatan molekuler, dan mengidentifikasi profil kimia dari isolat-isolat potensial. Sebanyak 21 isolat bakteri endofit telah berhasil diisolasi dari akar, batang, dan daun bidara. Dual-Culture Agar Diffusion Assay menunjukkan dua dari 21 isolat bakteri memiliki aktivitas antibakteri terhadap empat bakteri target. Estrak kasar metabolit sekunder kedua isolat potensial (80 mg/ml) mampu menghambat semua bakteri target dengan diameter zona hambat berkisar 8,3–15,0 mm. Nilai minimum inhibitory concentration (MIC) dan minimum bactericidal concentration (MBC) yang ditentukan dengan teknik microdilution menunjukkan bahwa kedua ekstrak tersebut memiliki nilai MIC berkisar antara 468,75–>30.000 µg/ml, dan MBC berkisar antara 468,75–>30.000 µg/ml. Berdasarkan analisis gen 16S rRNA, dua isolat potensial yaitu BBSB3 dan BDSB4 masing-masing memiliki kemiripan sekuens tertinggi dengan Pseudomonas aeruginosa strain DSM 50071 dan Pseudomonas aeruginosa strain N. Kedua isolat tersebut terdeteksi memiliki gen polyketide synthase I (PKS I) yang umumnya terlibat dalam biosintesis senyawa poliketida. Analisis liquid chromatograohy tandem mass spectrometry (LC-MS/MS) kedua ekstrak kasar menunjukkan keduanya memiliki berbagai senyawa aktif antibakteri., Infectious diseases caused by antibiotic-resistant pathogenic bacteria are one of the significant health problems worldwide. Exploring the antibacterial activity of endophytic bacteria associated with Ziziphus sp. may provide an alternative source of new antibiotics. This study aims to evaluate the antibacterial activity of endophytic bacteria isolated from Ziziphus sp., identify potential isolates through molecular approaches, and identify the chemical profiles of potential isolates. In previous research, 21 endophytic bacterial isolates were successfully isolated from Ziziphus sp. Antagonism assay showed that two of the 21 bacterial isolates had antibacterial activity against four target bacteria. At a concentration of 80 mg/ml, the crude extract of secondary metabolites of the two potential isolates could inhibit all target bacteria with inhibition zone diameters ranging from 8.3-15.0 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of both extracts ranged from 468.75–>30,000 µg/ml. Based on their 16S rRNA sequences, the selected isolates were closely similar to Pseudomonas aeruginosa strain DSM 50071, and Pseudomonas aeruginosa strain N. Both isolates were also detected to have the PKS I gene, which is generally involved in the biosynthesis of polyketide compounds. LC-MS/MS analysis of the two crude extracts showed both to have various antibacterial active compounds.
Keyword: 16S rRNA, LC-MS/MS, MIC, Pseudomonas aeruginosa, Gen PKS I

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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