Pengendalian Saprolegnia sp. pada Telur Gurami (Osphronemus gouramy) Menggunakan Isolat Bakteri Kitinolitik

Abstract

A study on potential antagonist activity of 24 chitinolytic bacteria isolated from Osphronemus gouramy pond culture to inhibit the Saprolegnia sp. causal agent of saprolegniasis in gouramy egg was carried out. The ability of bacterial isolates to inhibit the Saprolegnia sp. in vitro was evaluated by antagonism assay on minimum salt medium agar with 2% colloidal chitin as C source. Hyphal abnormality as a result of antagonistic assay was examined in this study. The result showed that 10 isolates, PB3A, PB01, PB02, PB05, PB08, PB10, PB13, PB14, PB15 dan PB17 showed relatively high inhibition zone. The diameter of inhibition zone ranged from 10-19 mm. The abnormality of miselium was lysis (40%), a lised hyphae tips (30%), bent hyphae (23,33%) and twisted hyphae (6,67%). Saprolegnia sp. was examined for its ability causing infection in egg. The result showed that this isolates caused infection on gouramy egg. Pathogenecity and attachment of bacteria assay was done to eliminate pathogen isolate and to know the ability of isolates to adhere on the egg mucosa. The result showed that PB01 was pathogen and all potential bacteria had ability to adhere to egg surface. It was proved by reisolation assay and examination on Scanning Electron Microscope (SEM). Potential chitinolytic bacteria were assayed to Saprolegnia sp. in vivo using gouramy egg. Potential bacteria (PB05, PB08, PB13, PB14, PB15, and PB17) could reduce mortality rate and increase hatching rate on infected egg. Based on this study, we concluded that PB05, PB08, PB13, PB14, PB15, and PB17 had the ability to inhibit the Saprolegnia sp. these isolates could be utilized as potential biological control candidates against Saprolegniasis.

Penelitian ini bertujuan untuk mengetahui potensi 24 bakteri kitinolitik yang diisolasi dari kolam budidaya ikan gurami (Osphronemus gouramy) untuk menghambat pertumbuhan isolat Saprolegnia sp. yang diisolasi dari telur gurami. Uji antagonisme dilakukan pada media garam minimum dengan 2% koloidal kitin untuk mengetahui kemampuan isolat bakteri menghambat Saprolegnia sp. Sepuluh isolat bakteri menunjukkan daya hambat dengan diameter 10–19 mm. Abnormalitas hifa diamati secara mikroskopis meliputi lisis (40%), lisis pada ujung hifa (30%), hifa bengkok (23,33%) dan hifa terpuntir (6,67%). Uji patogenesa isolat Saprolegnia sp. dilakukan untuk mengetahui kemampuan isolat tersebut menginfeksi telur gurami. Hasil penelitian menunjukkan bahwa isolat Saprolegnia sp. patogen terhadap telur. Uji patogenesa dan perlekatan bakteri potensial dilakukan untuk mengeliminasi isolat yang bersifat patogen dan tidak dapat melakukan perlekatan terhadap mukosa sel telur. Isolat PB01 bersifat patogen bagi telur sehingga tidak dapat digunakan sebagai pengendali hayati Saprolegnia sp. Semua isolat memiliki kemampuan melekat pada sel telur ditunjukkan dengan uji reisolasi dan pengamatan Scanning Electron Microscope (SEM). Uji tantang isolat bakteri potensial menghambat infeksi Saprolegnia sp. pada telur dilakukan pada bak percobaan dan kondisi terkontrol. Hasil penelitian menunjukkan bahwa 6 isolat bakteri yaitu PB05, PB08, PB13, PB14, PB15, dan PB17 mampu menurunkan tingkat mortalitas serta meningkatkan daya tetas telur yang yang diinfeksi Saprolegnia sp. sehingga potensial untuk dijadikan agen pengendali hayati Saprolegnia sp. pada telur gurami.