Judul: Identification of Bacterial Community in Vannamei Shrimp (Litopenaeus vannamei) from Two Different Market Locations Using Metagenomic Technology
Abstrak: Udang merupakan komoditas hasil perairan yang mudah mengalami proses kemunduran mutu, salah satunya disebabkan oleh aktivitas bakteri. Penggunaan media kultur dalam proses identifikasi komunitas bakteri menjadi kurang optimal, karena proses kultivasi tidak dapat menumbuhkan semua jenis bakteri. Penelitian ini bertujuan untuk mengidentifikasi komunitas bakteri yang terdapat pada komoditas udang segar dengan teknik metagenomik. Proses identifikasi bakteri dilakukan melalui tahap pengusapan permukaan udang, kemudian isolasi DNA bakteri menggunakan Wizard Genomic DNA Purification Kit dan amplifikasi menggunakan primer universal 16S rRNA dengan wilayah V3-V4. Proses sekuensing dilakukan menggunakan teknik Next Generation Sequencing. Komunitas bakteri yang teridentifikasi didominasi oleh filum Bacteroidota, Patescibacteria, Firmicutes, Fusobacteriota, Campilobacteriota, Actinobacteriota, dan Proteobacteria. Potensi kelompok bakteri patogen dan pembusuk pada udang teridentifikasi berasal dari genus Myroides, Flavobacterium, Pseudomonas, Aeromonas, Escherichia, Shigella dan Shewanella, Shrimp is an aquatic product that is prone to deterioration in quality, one of which is caused by bacterial activity. The use of culture media in the identification process of bacterial communities is less than optimal because the cultivation process cannot grow all types of bacteria. This study aims to identify the bacterial community found in fresh shrimp commodities with a metagenomic approach. The bacterial identification process was carried out by swabbing the surface of the shrimp, then isolating bacterial DNA using the Wizard Genomic DNA Purification Kit and amplification using a universal 16S rRNA primer with a V3-V4 region. The sequencing process was carried out using Next Generation Sequencing. The identified bacterial community was dominated by the phyla Bacteroidota, Patescibacteria, Firmicutes, Fusobacteriota, Campilobacteriota, Actinobacteriota, and Proteobacteria. Potential groups of pathogenic and spoilage bacteria in shrimp were identified from the genera Myroides, Flavobacterium, Pseudomonas, Aeromonas, Escherichia, Shigella, and Shewanella
Keyword: amplicon sequence variants, bakteri, DNA, udang

Judul: Kelimpahan dan Jenis Bakteri Vibrio pada Sedimen Tambak Udang Vaname Sebagai Deteksi Dini Serangan Penyakit Vibriosis
Abstrak: Komoditas akuakultur yang menjadi unggulan di Indonesia adalah udang vaname (Litopenaeus vannamei). Penyebab utama permasalahan pada budidaya udang adalah penyakit, salah satunya Vibriosis. Vibriosis merupakan penyakit yang disebabkan oleh bakteri Vibrio spp. Penyakit ini ditemukan pada budidaya udang di Tambak Pinang Gading, Lampung Selatan, Provinsi Lampung. Sedimen tambak merupakan tempat penguraian bahan organik dengan melibatkan aktivitas bakteri. Oleh karena itu, pengamatan mikroorganisme di sedimen tambak udang diperlukan untuk memitigasi kejadian penyakit dan penerapan manajemen kesehatan budidaya udang pada petak tambak budidaya. Tujuan penelitian ini untuk menganalisis kelimpahan dan jenis bakteri Vibrio pada sedimen tambak udang vaname sebagai deteksi dini serangan penyakit Vibriosis. Pengukuran kelimpahan bakteri (total bakteri, total bakteri Vibrio sp., total bakteri Vibrio koloni hijau, total bakteri Vibrio koloni kuning, dan total bakteri Vibrio parahaemolyticus) pada media budidaya dilakukan tiga kali, pada DOC 0, 29, dan 43 dengan pengenceran berseri metode cawan sebar untuk dihitung total koloninya. Pengambilan sampel dilakukan secara purposive dan composite. Dilakukan konfirmasi bakteri V. parahaemolyticus strain AHPND dengan nested PCR. Hasil penelitian menunjukkan kelimpahan bakteri Vibrio koloni hijau mendominasi selama pengambilan sampel. Bakteri V. parahaemolyticus pada sedimen budidaya udang telah terekspresi sejak awal masa budidaya. Outbreak penyakit vibriosis mengakibatkan penurunan produksi yang signifikan. Teridentifikasi lima isolat bakteri V. parahaemolyticus strain AHPND dari hasil penelitian. Kata kunci: kelimpahan bakteri, Litopenaeus vannamei, sedimen tambak, vibriosis, The leading aquaculture commodity in Indonesia is vannamei shrimp (Litopenaeus vannamei). The main cause of problems in shrimp farming is disease, one of which is Vibriosis. Vibriosis is a disease caused by the bacterium Vibrio spp. This disease was found in shrimp farming in Pinang Gading Ponds, South Lampung, Lampung Province. Pond sediment is a place for the decomposition of organic matter by involving bacterial activity. Therefore, observation of microorganisms in shrimp pond sediments is necessary to mitigate disease incidence and to implement shrimp farming health management in aquaculture ponds. The purpose of this study was to analyze the abundance and types of Vibrio bacteria in vannamei shrimp pond sediments as an early detection of Vibriosis disease. Measurement of bacterial abundance (total bacteria, total Vibrio sp. bacteria, total green Vibrio colony bacteria, total yellow Vibrio colony bacteria, and total Vibrio parahaemolyticus bacteria) in the culture media was carried out three times, at DOC 0, 29, and 43 with serial dilution method scatter plates to count the total colonies. Sampling was carried out purposively and compositely. Confirmation of V. parahaemolyticus strain AHPND was carried out by nested PCR. The results showed that the abundance of green colony Vibrio bacteria dominated during sampling. V. parahaemolyticus bacteria in shrimp culture sediments have been expressed since the beginning of the culture period. Outbreak of vibriosis resulted in a significant decrease in production. Five isolates of V. parahaemolyticus strain AHPND were identified from the research results. Keywords: bacterial abundance, Litopenaeus vannamei, sediment pond, vibriosis
Keyword: kelimpahan bakteri, Litopenaeus vannamei, sedimen tambak, vibriosis, bacterial abundance, sediment pond, vibriosis

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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