Demetilasi metilmekuri oleh bakteri yang diisolasi dari sedimen Sungai Sangon

SUHERYANTO, Promotor Prof. Dra. Hj. Endang Sutariningsih Soetarto, M.Sc., Ph.D

2010 | Disertasi | S3 Ilmu Lingkungan

Penelitian tentang "demetilasi metilmerkuri oleh bakteri yang diisolasi dari sedimen Sungai Sangon" telah dilakukan. Penelitian ini bertujuan untuk mempelajari keberadaan spesies merkuri di sedimen Sungai Sangon dan transfomasi metilmerkuri oleh aktivitas bakteri indigenous. Tujuan spesifik penelitian adalah (1) menentukan tingkat pencemaran total merkuri dan metilmerkuri di sedimen Sungai Sangon, (2) mendapatkan bakteri indigenous yang resisten terhadap metilmerkuri dan berperan aktif dalam demetilasi metilmerkuri, (3) mengkaji mekanisme demetilasi metilmerkuri oleh isolat bakteri indigenous. Penelitian diawali dengan menganalisis total merkuri dan metilmerkuri di sedimen Sungai Sangon menggunakan metode CV-AAS (Cold Vapor Atomic Absorption Spectrometry) dan Gas Liquid Chromatography (GLC). Hasil penelitian menunjukkan bahwa konsentrasi total merkuri dan metilmerkuri bervariasi. Konsentrasi total merkuri daerah hulu adalah 236,67 ng/g, tengah 154,25 ng/g, dan hilir 70,25 ng/g. Sementara itu, konsentrasi metilmekuri daerah hulu adalah 48,50 ng/g, tengah 96,25 ng/g, dan hilir 55,00 ng/g. lsolasi bakteri dilakukan secara langsung dan tidak langsung melalui teknik kultur diperkaya. Penelitian ini menemukan 82 isolat bakteri pengguna metilmekuri. Setelah melalui seleksi, hanya 6 isolat bakteri yang resisten dan tumbuh menggunakan metilmerkuri. lsolat tersebut adalah strain SDM 41 , SDM 78, SDM 81 , SDPM 8a, SDPM 8b, dan SDPM 24. Uji kemampuan demetilasi metilmerkuri dilakukan melalui percobaan pertumbuhan. Kemampuan demetilasi metilmerkuri bakteri ditunjukkan dengan penurunan konsentrasi metilmerkuri pada fasa eksponensial akhir pertumbuhan. Kemampuan demetilasi tertinggi ditunjukkan oleh strain SDM 81 dan SDPM 8a. Mekanisme demetilasi metilmerkuri diawali dengan terlepasnya gugus metil (- CH3) dan dihasilkan ion merkuri (Hg+2) . Hasil aktivitas protein spesifik pada Elektroforesis gel PAGE dan NATIVE menunjukkan pelepasan ion Hg+2 akibat aktivitas enzim organomerkuriliase dengan berat molekul 19 - 27 kDa. Keenam isolat bakteri berhasil diidentifikasi dengan alat BD Phonix dan mempunyai karakter yang spesifik dalam demetilasi metilmerkuri. Keenam isolat bakteri mempunyai kemiripan dengan Brevundimonas diminuta (strain SDM 41), Bacillus cereus (strain SDM 78), Empedobacter brevis (strain SDM 81), Klebsiella pneumoniae (strain SDPM 8a), Pseudomonas aeruginosa (strain SDPM 8b) dan Spingomonas paucimobilis (strain SDPM 24).

Research about "demethylation methylmercury by bacteria isolated from sediment Sangon River has been done. The aim of this research was to reveal the fate of the methylmercury in the sediment of Sangon River and the transformation of methylmercury by indigenous bacteria activities. Specifically, this research consisted of (1) determination of total mercury and methyl mercury contamination in River Sangon sediment, (2) isolation of indigenous bacteria, which had resistant to methylmercury and had active role in methylmercury demethylation, (3) learning mechanism of methylmercury demethyilation by indigenous isolated bacteria. At the beginning, total mercury and methylmercury in Sangon River sediment were analyzed using Cold Vapour Atomjc Absorption Spectrometry (CV-AAS) and Gas Liquid Chromatography (GLC) methods. Results indicated that contamination of total mercury and methylmercury varied. The concentrations of total mercury in upstream were 236.67 ng/g, midle 154.25 ng/g, downstream 70.25 ng/g, while the concentrations of methylmercury in upstream were 48.50 ng/g, midle 96.25 ng/g downstream 55.00 ng/g. Based on the growing ability in methylmercury contamination, the isolation of bacteria was conducted using direct and indirect methods, by means of culture technique with the once harvest systems. This research found 82 isolated from Sangon River sediment which were able to tolerate the methylmercury. However, only 6 bacteria isolated exhibited resistance to methylmercury. These were strain SDM 41 , SDM 78, SDM 81, SDPM 8a, SDPM 8b, and SDPM 24. The demethylation ability of the strains towards methylmercury was investigated by growth test. The demethylation ability of bacteria was indicated by the decrease in methylmercury concentration at final exponential phase of growth. The highest decrease of methylmercury concentration was shown by SDM 81 and SDPM 8a strain. The demethylation mechanism was begun with realising -CH3 group and producing mercury ion (Hgl. The specific protein activity at gel of PAGE and NATIVE Electrophoresis showed the release of Hg +2 was caused by organomercuryliase enzyme activity. It had 19- 27 kDa molecul weight. These six isolated bacteria had been successfully identified using BD Phonix method and showed the specific character in methylmercury demethylation. These six isolates were similar to Brevundimonas diminuta (strain SDM 41 ), Bacillus cereus (strain SDM 78), Empedobacter brevis (strain SDM 81 ), Klebsiella pneumoniae (strain SDPM 8a), Pseudomonas aeruginosa (strain SDPM 8b) and Spingomonas paucimobilis (strain SDPM 24).

Kata Kunci : Demetilasi,Metilmerkuri,Isolat bakteri,Sedimen,Sungai Sangon