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Abstrak :
Telah dilakukan penelitian untuk mengetahui laju fiksasi nitrogen strain-strain Nostoc [Vaucher 1803] Bornet et Flahault 1886. Penelitian menggunakan 8 strain Nostoc koleksi Laboratorium Taksonomi Tumbuhan, Departemen Biologi, FMIPA UI. Penelitian menggunakan metode Acetylene Reduction Assay (ARA) dengan 2 ulangan untuk setiap strain Nostoc. Pengujian dilakukan pada strain yang telah berumur 21 hari. Biomassa berat basah strain Nostoc yang digunakan adalah 0,1 gram. Masing-masing strain diinkubasi selama 30, 60, dan 90 menit dengan menambahkan 1 ml gas asetilen. Hasil penelitian menunjukkan data yang bervariasi untuk masing-masing strain Nostoc pada masing-masing waktu inkubasi. Sebanyak 6 strain Nostoc menunjukkan nilai laju fiksasi nitrogen tertinggi pada waktu inkubasi 30 menit. Sebanyak 2 strain Nostoc menunjukkan nilai laju fiksasi nitrogen tertinggi pada waktu inkubasi 60 menit. Strain Nostoc BTM6-02 menunjukkan nilai laju fiksasi nitrogen yang paling tinggi yaitu 3892,5 μmol (dicapai pada inkubasi 60 menit). Strain Nostoc CPG24 menunjukkan nilai laju fiksasi nitrogen yang paling rendah, yaitu 292,44 μmol (dicapai pada inkubasi 90 menit). ......The research of nitrogen fixation rate of Nostoc [Vaucher 1803] Bornet et Flahault 1886 have been done. Eight strains of Nostoc from Plant Taxonomy Culture Collection, Department of Biology, Faculty of Mathematics & Natural Sciences, University of Indonesia, were used. The measurement of nitrogen fixation used Acetylene Reduction Assay (ARA) method with 2 samples for each strain. Experiments were conducted using strains at 21st day age. Wet weight of each strain was 0.1 gram. Then, each Nostoc strain was incubated with addition of 1 ml acetylene for 30, 60, and 90 minutes. The experiment result showed a different value for each Nostoc strain in every incubation times. Six Nostoc strains showed the highest value of nitrogen fixation after incubated for 30 minutes. Two Nostoc strains showed the highest value of nitrogen fixation after incubated for 60 minutes. Nitrogen fixation rate of BTM6-02 reached the highest value of 3892.5 μmol after incubated for 60 minutes. Nitrogen fixation rate of CPG24 was the lowest ones (292.44 μmol) after incubated for 90 minutes.

Abstrak :
Telah dilakukan penelitian mengenai potensi bakteri basil indigenous sebagai plant growth promoting bacteria (PGPB). Isolat G7, G10 dan G18 yang berpotensi dalam meningkatkan pertumbuhan tanaman diisolasi dari saluran pencernaan larva lalat tentara hitam, sedangkan isolat B. siamensis LDR dengan potensi sebagai agen biokontrol diisolasi dari cocopeat. Penelitian ini dilakukan untuk untuk mengetahui karakterisasi pertumbuhan dari isolat G7, G10 dan G18, meliputi pH medium (5, 6, 7, 8, 9) dan suhu inkubasi (30, 40, 50 oC). Uji antagonisme dilakukan antara isolat G7, G10 dan G18 dengan B. siamensis LDR guna melihat kemungkinan isolat-isolat tersebut untuk disatukan dalam satu konsorsium. Uji kemampuan memfiksasi nitrogen dan memproduksi siderofor dilakukan pada isolat G7, G10, G18 dan B. siamensis LDR.  Hasil menunjukkan bahwa isolat G7, G10 dan G18 dapat tumbuh pada pH 5—9 dengan pertumbuhan optimum pada kisaran pH 7—9. Suhu optimum bagi ketiga isolat diketahui pada 40 oC. Terdapat hubungan antagonisme isolat G7, G10 dan G18 terhadap B. siamensis LDR sehingga isolat-isolat tersebut tidak dapat disatukan dalam satu konsorsium. Kemampuan memfiksasi nitrogen ditunjukkan oleh isolat G7 dan G10. Kemampuan memproduksi siderofor dimiliki oleh semua isolat, yaitu G7, G10, G18 dan juga B. siamensis LDR. Isolat G7 dan G10 yang mampu memfiksasi nitrogen serta memproduksi siderofor merupakan isolat yang lebih unggul karena memiliki karakteristik PGPB yang lebih lengkap. ......Research has been carried out on the potential of several indigenous bacili bacteria as plant growth promoting bacteria (PGPB). Isolates G7, G10 and G18 with potential to increase plant growth were isolated from the digestive tract of black soldier fly larvae, while B. siamensis LDR with potential as a biocontrol agent was isolated from cocopeat. This research was conducted to determine the growth characteristics of isolates G7, G10 and G18, including medium pH (5, 6, 7, 8, 9) and incubation temperature (30, 40, 50 oC). Antagonism test was carried out between isolates G7, G10 and G18 against B. siamensis LDR to see the possibility of these isolates to be combined in one consortium. The ability to fix nitrogen and produce siderophores were carried out on isolates G7, G10, G18 and B. siamensis LDR. The results showed that isolates G7, G10 and G18 could grow at pH 5—9 with optimal growth in the range of pH 7—9. The optimum temperature for the three isolates was at 40 oC. There was an antagonistic relationship between isolates G7, G10 and G18 towards B. siamensis LDR so these isolates could not be combined into one consortium. The ability to fix nitrogen was shown by isolates G7 and G10. The ability to produce siderophores was shown by all isolates, namely G7, G10, G18 and also B. siamensis LDR. Isolates G7 and G10 which are able to fix nitrogen and produce siderophores, were the best isolates because they have more complete characteristics as PGPB.