Flavobacterium columnare, the causative agent of "columnaris disease" , is one of the most important bacterial pathogens in freshwater fishes (Wakabayashi, 1993). It was first isolated by Davis in 1922, and named Bacillus columnaris. The organism was variously reclassified as Chondrococcus columnaris (Ordal and Rucker, 1944), Cytophaga columnaris (Garnjobst, 1945) and Flexibacter columnaris (Leadbetter, 1974). The bacterium now belongs to Flavobacterium after Bernardet et al. (1996) amended the description of this genus. Song et al. (1988) found three types of colony morphology among Fl. columnare strains isolated from wide geographical areas, that is, rhizoid, mucoid and honeycomb-like type colonies. Anacker and Ordal for 18-20 h. 16S rDNA amplification The universal primers of 20F and 1500R were used to amplify 16S rDNA and their sequences are 5 '-AGAGTTTGATC(AC)TGGCTCAG-3' (position at 8 to 27 E. coli numbering) and 5'-CGATCCTACTTGCGTAG-3' (position at 1510 to 1492 E. coli numbering), respec tively (Weisburg et al., 1991). PCR amplification was performed in 50 ,ƒÊL containing 1.5 mM MgCl2, 0.5 nM of each dNTP (the nucleotide triphosphate of adenine, guanine, cytosine and thymine), 10 pM of each primer, 2.5 units of Taq polymerase and 400 ng of purified DNA. Samples were subjected to 30 cycles of amplification in a DNA thermal cycler (Gene AmpPCR System 2400, Perkin-Elmer). RFLP analysis PCR products were cut with restriction endonu cleases Haelll, Hhal, Mspl , Hinfl and Rsal. Digested fragments were separated by Mupid mini-gel electro phoresis aparatus with 3% NuSieve agarose. The results were detected by staining with 0.3-0.5% ethidium bromide for 30 min. 16S rDNA sequencing Sequencing of the PCR-amplified 16S rDNA was performed with the ABI Prism 377 DNA sequencer according to the protocol recommended by the manu facturer. Sequence data were compiled and binary sequence similarities were calculated with the GENETIX MAC (Software Development Co., Tokyo, Japan). The nucleotide substitution rate (Knuc values) (Kimura, 1980)

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We isolated a marine bacterium strain S2V2 which inhibited the growth of pathogenic marine Vibrio spp. The aims of this research were to identify a new antibioticproducing marine bacterium strain S2V2, and evaluate its spectrum activity and pathogenic property. Analysis of 16S rDNA sequence placed strain S2V2 in the genus Pseudoalteromonas, but the sequence similarity was low (95.46%) implying the strain might be a new species in this genus. Strain S2V2 inhibited the growth of 67.9% of 28 Vibrio strains tested. This strain inhibited V. alginolyticus, V. anguillarum, V. fluvialis, V. harveyi, V. metschnikovii, V. splendidus, V. ordalii, V. parahaemolyticus, and V. vulnificus, but inactive against V. campbellii, Aeromonas hydrophyla and Staphylococcus aureus. Strain S2V2 produced extracellular non proteinaceous antibacterial substances. The highest antibacterial activity was found when strain S2V2 was cultured for 96 h in ZoBell broth medium. An artificial infection to post larvae of Lithopenaeus vanname indicated that strain S2V2 was a non pathogenic bacterium. Non pathogenic property and specific antibacterial activity against a broad range of fish pathogenic marine Vibrio of strain S2V2 suggest that this strain is a prospective source of unique antibiotic and a potential biocontrol agent in marine aquaculture.

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Rawa pesisir merupakan rawa pasang-surut bagian dari ekosistem estuari. Rawa pesisir di Sungai Cimandiri Kabupaten Sukabumi, Jawa Barat merupakan salah satu ekosistem estuari yang memiliki peran ekologi yang penting untuk kehidupan biota air yang menetap maupun yang bermigrasi seperti ikan sidat.  Penelitian ini bertujuan untuk mengkaji fungsi rawa pesisir, biologi populasi sidat dan faktor lingkungan yang berpengaruh terhadap populasi sidat  Penelitian dilakukan secara parsial pada  September-Oktober 2016, Maret dan Desember 2017 dan January-November 2018. Penangkapan ikan sidat dan pengukuran kualitas air dilakukan pada 4 lokasi terpilih berdasarkan kondisi habitat yang berbeda.  Penangkapan ikan sidat dilakukan pada malam hari dengan alat tangkap pancing dan bubu.  Sidat yang tertangkap terdiri dari 2 jenis yaitu Anguilla bicolor bicolor  (107 individu) dan Anguilla marmorata (4 individu). Panjang total A. bicolor bicolor adalah 15,7-57,0 cm dan berat 5,8-347,2 g dan panjang total  A. marmorata adalah 17,0-29,5 cm dan berat 6,9-33,7 g.  Pola pertumbuhan sidat (A.bicolor bicolor) di rawa pesisir adalah allometrik negatif, dengan nilai faktor kondisi 0,99-1,03.  Sidat di rawa pesisir banyak tertangkap di daerah rawa pesisir yang dalam dan terdapat tumbuhan air. Berdasarkan analisis PCA (Principal Component Analysis), preferensi keberadaan sidat di rawa pesisir dicirikan oleh parameter kedalaman, kecerahan, salinitas, dan kecepatan arus. Rawa pesisir diketahui berfungsi sebagai habitat bagi ikan sidat muda (yellow eel) pada fase estuarine.

In this study the crude ethyl acetate extracts and fractions from red algae Gracilaria edulis were studied against fish pathogens. G. edulis was extracted with ethyl acetate, fractionated in silica gel coloum chromatography and gradient hexane-ethyl acetate. The extract and fractions were subjected for bioassay guided isolation against fish pathogen Vibrio spp and Aeromonas hydrophila. Bioassays were accomplished by diffusion agar, bioauthography, and 96 well microplates format. Profiling chemical constituent was done by thin layer chromatography and GC-MS. Metabolites analysis using GC-MS yielded chemical constituents of active fractions as 9-hexadecenoic acid, hexadecanoic acid, 13-octadecenoic acid, 10-octadecenoic acid, eicosanoic acid, cholest-8-en-3-ol. The results provide in vitro scientific support to the possible application of Gracilaria edulis as antimicrobial agent that may contribute for treatment of bacterial infections in aquaculture.

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