KARAKTERISASI DAN IDENTIFIKASI BAKTERI PELARUT FOSFAT DARI LAHAN YANG TERKENA ERUPSI MERAPI 2010

SENLIE OCTAVIANA, Drs.Langkah Sembiring, M.Sc.,Ph.D

2012 | Tesis | S2 Bioteknologi

Penelitian mengenai bakteri pelarut fosfat dilakukan untuk mengetahui peran komunitas mikrobia tanah dalam memacu aktivitas mobilisasi senyawa fosfat dari material vulkanik Gunung Merapi. Penelitian difokuskan pada isolasi bakteri pelarut fosfat (BPF), serta analisis komunitas bakteri pada material vulkanik. Objek penelitian berasal dari tanah sampel yang terkena erupsi Merapi dalam selang waktu 1, 3 dan 6 bulan. Aktivitas bakteri tanah dideteksi dengan teknik fluorescein diacetat (FDA). Bakteri tanah yang terdeteksi dengan FDA dianalisis diversitasnya dengan teknik denaturing gel gradient electroforesis (DGGE) berdasarkan gen 16S rRNA (culture independent) dan diisolasi dengan menggunakan medium Pikovskaya berdasarkan indeks zona jernih (culture dependent). Isolat bakteri yang diperoleh tersebut diseleksi dan diuji aktivitasnya dalam pelarutan fosfat pada medium Calsium Phosphate, Alumunium Phosphate dan penghasilan hormon auksin. Konfirmasi sifat yang dimilikinya sebagai agen biofertilizer dideteksi berdasarkan 4 gen fungsional yang terlibat dalam pelarutan fosfat, penghasil hormon auksin, fiksasi nitrogen dan nitrifikasi. Selanjutnya isolat BPF terpilih dikarakterisasi dan diidentifikasi berdasarkan sistematik molekular dengan menggunakan sekuense gen 16S rRNA. Hasil penelitian berdasarkan Profil DGGE 16S rRNA, komunitas bakteri di lahan yang terkena erupsi Merapi membutuhkan rentang waktu 6 bulan untuk recovery keanekaragaman strain dalam komunitas. Sebanyak 23 koloni isolat bakteri pelarut fosfat berhasil diisolasi dan hanya 9 isolat yang mampu menunjukkan aktivitas pelarutan fosfat pada medium Alumunium-Fosfat dan atau aktivitas produksi auksin yaitu isolat BS1F, BS2K, BS3ML2, BS4ML4, BS6TM1, BS7TM2, BS14E601 dan BS15E032. Kesembilan isolat terdeteksi memiliki 4 gen fungsional yang bervariasi dan isolat BS2K paling banyak gen fungsionalnya di antara 9 isolat. Berdasarkan analisis sekuen molekular 16S rRNA, kesembilan isolat teridentifikasi sebagai anggota genus Burkholderia (BS1F, BS2K, BS3ML2, BS6TM1, BS7TM2), Enterobacter (BS14E601 & BS15EO32), Klebsiella (BS13E301) dan Bacillus (BS4ML4). Dengan demikian, kecepatan perubahan (recovery) komunitas bakteri membutuhkan rentang waktu 6 bulan dan pada lahan yang terkena erupsi tersebut dapat ditemukan 3 bakteri pelarut fosfat yang mampu menghasilkan hormon auksin yang berpotensi meningkatkan kesuburan tanah di lahan yang terkena erupsi Merapi.

The research on phosphate solubilizing bacteria was carried out to understand the role of the soil microbial community encompassing to mobilization activities of the phosphate from the effect of changing physicochemical conditions caused by volcanic eruption Mount Merapi. The study was focused on isolation of phosphate solubilizing bacteria (PSB) and bacterial community structural analyses of soil as affected by volcanic materials at sampling site. The soil and volcanic material were collected from Merapi areas within interval of 1, 3, and 6 months. Hydrolytic activities of soil bacteria were detected with fluorescein diacetat technique (FDA). Samples which were positively detected of FDA method, were subsequently analysed for diversity of soil bacteria by using Denaturing Gel Gradien Electrophoresis (DGGE). In addition, from the same sample, PSB were selectively isolated by using Pikovskaya medium based on the clear zone index value. The selected bacterial isolates were tested for their activities in solubilizing phosphate using different phosphate (Ca-P and Al-P) and in producing auxin. Based on phosphate solubilizing and in producing auxin, the isolates were subquently selected. There genetic characters as biofertilizer agents were also determined by detecting 4 functional genes involved in solubilizing phosphate, auxin production, nitrogen fixation, and nitrification. The selected isolates were characterize molecularly based on 16S rRNA gene sequences. The results of the study showed that community of soil bacteria on Merapi eruption-affected area was susceptible to physicochemical of environment and it took 6 months for it recovery. A total of 23 isolates of bacterial colonies were isolated and only 9 isolates which were able to demonstrate solubilizing phosphate (Al-P) medium and or producing auxin of the isolates namely BS1F, BS2K, BS3ML2, BS4ML4, BS6TM1, BS7TM2, BS14E601 and BS15E032. The nine isolates were detected to have a variety of 4 functional genes and only BS2K was found to have all the 4 functional gene. Based on 16S rRNA molecular analysis, the selected isolates were identified to be member of genus Burkholderia (BS1F, BS2K, BS3ML2, BS6TM1, BS7TM2), Enterobacter (BS14E601 & BS15EO32), Klebsiella (BS13E301) and Bacillus (BS4ML4). Therefore, the phosphate solubilizing and auxin producing bacteria could be obtained from samples collected from Mount Merapi eruption-affected area. Furthemore, it was also observed bacterial comunity could only recovery require 6 months.

Kata Kunci : Lahan terkena erupsi Merapi, Bakteri Pelarut Fosfat .