Judul: Isolation and Characterization of Acyl Homoserine Lactonase (AHL-lactonase) Producing Bacteria from Agricultural Field in Java
Abstrak: Quorum sensing (QS) is a bacterial communication mechanism correlating with the number of bacterial population and accumulation of autoinducer (AI). Quorum sensing in Gram-negative bacteria involves a AI group of acyl homoserine lactone (AHL) to regulate the expression of several genes, including virulence genes. Anti-quorum sensing compounds can degrade AHL so that virulence genes can not be expressed. Acyl homoserine lactonase (AHL-lactonase) encoded by the aiiA gene is one enzyme that can act as an anti-quorum sensing. This study aimed to isolate and characterize the AHL-lactonase producing bacteria isolated from agricultural field in Java. Activity of AHL degradation bioassay using Chromobacterium violaceum as a bacterial indicator. Verification the presence of AHL-laktonase was performed by gene aiiA amplification. As many as 12 bacterial isolates showed AHL degradation activity and two isolates had the aiiA gene i.e. INT1c and SGT3g isolates. These isolates had bacil cells with chain arrangement and endospores. They were grouped in Gram-positive bacteria. AiiA gene sequence analysis showed that aiiA gene of INT1c had homology with aiiA gene of Bacillus cereus ATTCC 14579 while the SGT3g isolate had homology with aiiA gene of Bacillus thuringiensis BMB171. Molecular identification based on 16S rRNA gene showed that INT1c isolate had the closest similarity with the Bacillus cereus strain GM3 (98%) while SGT3g isolate had the closest similarity with the Bacillus thuringiensis strains A1-1 (99%).
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Judul: Isolasi dan karakterisasi bakteri penghasil ahl-laktonase asal lahan pertanian luar Pulau Jawa
Abstrak: Quorum sensing (QS) is communication between bacterial cells mediated by autoinducer (AI) to regulate the expression of specific genes in certain bacterial population quorum. AI of Gram negative bacteria is N-acyl homoserine lactone (AHL). QS system controls behaviors of bacterial population on biofilm formation, virulence, bioluminescence, and formation of antibiotics. QS process can be inhibited by anti-QS compound. AHL-lactonase is one of anti-QS compound encoded by aiiA gene. The aims of this study were to isolate and characterize bacteria producing AHL-lactonase from agricultural land outside Java. Soil samples were taken from 16 locations of agricultural lands. Bioassay was performed by AHL degradation of Chromobacterium violaceum. Detection of aiiA gene was conducted using specific primer aiiAF and aiiAR, while molecular identification was conducted based on 16S rRNA gene sequence. It was found that from 58 isolates, six isolates had AHL degradation activity i.e. PAD1a, BAL2a, NTT3a, NTT3e, NTT6B6, dan NTT6B7 isolates. Two isolates (i.e. NTT3a and NTT3e isolates) had aiiA gene. And indicated by 800 bp product. They were 99% closely related to AHL-lactonase gene from Bacillus sp 91.
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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