KARAKTERISASI DAN IDENTIFIKASI AEROBIC METHANE OXIDIZING BACTERIA (MOB) SEBAGAI PENURUN EMISI GAS METANA DI TANAH SAWAH

ANGGA PREMANA, Prof. Langkah Sembiring, M.Sc., Ph.D.

2013 | Tesis | S2 Biologi

Tujuan penelitian ini adalah untuk mengetahui keanekaragaman oxidizing bacteria (MOB) serta kemampuannya dalam mengoksidasi gas metana pada tanah persawahan yang telah diberi berbagai variasi perlakuan (salinitas, sumber karbon, dan pupuk). Varietas padi yang digunakan dalam penelitian ini adalah Ciherang dengan jumlah total 39 pot. Media tanam diukur paramater fisikokimiawi dengan menggunakan pH meter. Pada saat padi berumur 2 minggu dan 12 minggu dilakukan pengukuran emisi metana in situ dengan menggunakan Gas Detector. Proses isolasi MOB dilakukan dengan metode culture dependent dan culture independent. Isolasi culture independent dilakukan dengan mengisolasi total DNA bakteri tanah, setiap perlakuan dan diuji keberadaan MOB dengan deteksi gen pmoA. Hasil amplifikasi gen pmoA selanjutnya dianalisis dengan DGGE untuk mengetahui diversitas MOB. Isolasi culture dependent dilakukan untuk mendapatkan isolat MOB. Konsorsium bakteri MOB diuji kemampuan oksidasi metana dengan menggunakan GC. Isolat yang ditemukan selanjutya diisolasi DNA bakterinya dan diamplifikasi dengan gen pmoA, mxa dan 16S rRNA. Isolat yang positif terdeteksi memiliki gen tersebut dilakukan proses generic assignment dan sequencing gen 16S rRNA. Hasil dari penelitian ini menunjukkan bahwa MOB pada tanah sawah yang telah diberi perlakuan beda pupuk, salinitas dan sumber karbon memiliki struktur komunitas yang berbeda. Padi sebelum berbulir menunjukkan emisi metana yang lebih tinggi daripada padi setelah berbulir. Penurunan emisi metana pada perlakuan yang diberi pupuk NPK menunjukkan nilai yang lebih tinggi dibandingkan dengan bioaktivator. Pada perlakuan sumber substrat, emisi metana tertinggi pada perlakuan media tanam kompos yang ditambah jerami. Dari kedua strain (AP37 dan AP41) memiliki gen fungsional pmoA dan mxa. Strain AP37 diduga kuat sebagai strain anggota genus Pantoea sedangkan strain AP41 diduga kuat sebagai strain anggota genus Ralstonia.

The purpose of this research was to determine the diversity of methane oxidizing bacteria (MOB) and their ability to oxidize methane gasses in rice fields that have been given various treatments (salinity, carbon source, and fertilizer). The rice variety used in this research was the Ciherang rice with a total number of 39 pots. The planting media was measured for its physiochemical parameters using a pH meter. When the rice reaches 2 weeks and 12 weeks of age, an in situ methane gauging was performed using a Detector. The MOB isolation processes were carried out using culture dependent and culture independent methods. Culture independent isolation was performed by totally isolating soil bacteria DNA on each treatment, and then the MOB presence was tested using a pmoA gene detection. The result of pmoA gene amplification was then analyzed using the DGGE to determine the MOB diversity. Culture dependent isolation was performed to obtain MOB isolates. MOB consortium was tested for its oxidation capacity by using GC. The found isolates were then isolated of their bacteria DNA and then amplified using pmoA gene, mxa and 16S rRNA. Isolates that were positively detected having the said gene were subjected to a generic assignment process and a 16 rRNA gene sequencing. The results of this research shows that MOB in rice fields that have been given different treatments of fertilizer, salinity and carbon source have different community structures. Rice plants before bearing grains show higher methaneemission than when bearing grains. The reduction of methane emission on NPK fertilizer treatment shows higher value compared with the bioactivator. On substrate source treatment, the methane emission reduction was highest on rice-straw-added compost plant media treatment. Both strains (AP37 and AP41) have pmoA and mxa functional genes. AP37 strain was strongly suspected as a member of the Pantoea genus, while AP41 strain was strongly suspected as a member of the Ralstonia.

Kata Kunci : metana, tanah sawah, bakteri methanotrophic, oksidasi metana