Judul: Penapisan dan Identifikasi Bakteri Rhizosfer Padi Penghasil Asam Indol Asetat pada Kondisi Salin
Abstrak: Increased salinity in farmland due to the rising sea level have an impact on ion balance, an increased of ethylene in roots, caused of hypo-osmotic condition in roots, and finally hinder the growth of root. Utilization of indigen rhizobacteria with ability to produce growth phytohormone indole-3-acetic acid (IAA) could become one of solution of this problem. This research aims to screening a number of rhizobacteria which have ability of producig phytohormone IAA and tolerant of salinity stress. A total of 48 rhizobacteria isolates from coastal rice field of Patimban and Eretan, west Java have been analyzed. Isolates Er B1.3 and Er B1.7a have ability to grow on minimal salt medium content with 15 % NaCl. Both isolates are still capable of producing IAA with consecutive concentrations at 11 ppm and 3.1 ppm on minimal medium salt content with 10 % NaCl. IaaM gene identification results prove that isolates Er B1.3 and Er B1.7a producing IAA through the IAM pathway. Based on the result of sequencing 16S Rrna gene known that isolate Er B1.3 and Er B1.7a belong to genus Brevibacterium and Aeromonas, respectively.
Keyword: Bogor Agricultural University (IPB), salinity stress tolerance, IAA production, rhizobacteria

Judul: Penapisan Bakteri Rhizosfer Padi Penghasil Nitrogenase yang Tahan Kondisi Salin dan Identifikasi Gen nifH
Abstrak: The ability of nitrogen fixing by rhizosfer bacteria could be used to decrease salinity impact in coastal rice field. It was caused by nitrogenase, encoded by nifH gene in component II. The objectives of this research were to screen of rhizosfer bacterias that have the nitrogenase activity in saline condition and identify the presence of nifH gene. The fifty isolates of rhizosfer bacteri isolated from coastal rice field Eretan and Patimban region, West Java was analyzed. Five isolates showed the nitrogenase activity under saline condition, are Er B1 3, Er B1 4, Er B1 9, Er B2 10 dan Ptb B1 4. The identification of nifH gene from these 5 samples using polymerase chain reaction (PCR) showed that the size is ~360 bp. The highest activity of nitrogenase used acetylene reduction assay (ARA) was showed by Er B2 10 is 4,4081 μmol.mL-1hour-1.
Keyword: rhizosfer bacteria, nitrogenase activity, nifH gene, coastal soil, ARA

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf