Kemampuan Bakteri Kitinolitik dalam Menghambat Infeksi Aspergillus Sp. pada Ikan Nila (Oreochromis Niloticus)

Abstract

A study on ability of chitinoltytic bacteria to inhibit the Aspergillus sp. causal agent of disease in Tilapia fish has been done in the Laboratory of Microbiology Karantina Ikan Kelas I Polonia, Medan and Laboratory of Microbiology, Department of Biology, Faculty of Mathematics and Natural Sciences, University of Sumatera Utara, Medan. Four suspected pathogenic fungi i.e.Aspergillus sp. 1, Aspergillus sp. 2, Rhizopus sp. and Sp. 1 were isolated from Tilapia fish and koi goldfish eggs. Pathogenic test showed that Aspergillus sp. 2 was more pathogenic than the others, of which 70% of fish were affected. The ability of bacterial isolates to inhibit the fungal in vitro was evaluated by antagonism assay with dual plate on agar MSMC. The result of in vitro antagonism assay of all fungal isolation to six chitinolytic bacteria(Bacillus sp. BK13, Enterobacter sp. BK15, PB08, PB15, Enterobacter sp. PB17 dan Bacillus sp. BK17) showed the ability of bacterial isolate to inhibit fungal growth with to some extent. Antagonistic test showed that bacterial isolate Enterobacter sp. PB17 and Bacillus sp. BK17 inhibited more of all fungal growth. However, bacterial isolate inoculation prior Aspergillus spore inoculation in fish showed that Bacillus sp. BK17 was more capable of suppressing fungal disease, of which 92% of fish were healthy. Observation using Scanning Electron Microscope of fish skin showed that the bacterial isolate might attach to the fish, so capable possibility of suppressing pathogen in fish.