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Abstrak :
Penelitian ini bertujuan untuk memperoleh isolat Actinobacteria termofilik potensial dari tanah di sekitar geiser Cisolok yang dapat mendegradasi xylan dan mengetahui hubungan kekerabatannya dengan taksa terdekat dari Actinobacteria penghasil xylanase. Tujuh belas isolat Actinobacteria termofilik diisolasi dari tanah di sekitar geiser Cisolok, Jawa Barat. Penapisan kemampuan 17 isolat Actinobacteria dan type strain Actinomadura keratinilytica NBRC 105837T mendegradasi xylan dilakukan menggunakan medium Minimal (Mm) padat dengan penambahan substrat xylan 0,5, inkubasi selama 7 hari. Pewarnaan dengan Congo red 0,2 (b/v) menunjukkan terbentuknya zona bening di sekitar koloni isolat Actinobacteria yang dapat mendegradasi xylan 0,5 pada suhu 45 C (15 isolat), 50 C (14 isolat), 55 C (4 isolat), dan 60 C (3 isolat). Type strain NBRC 105837T dapat mendegradasi xylan 0,5 pada suhu 45 C hingga 60 C. Tiga isolat (SL1- 2-R-2, SL1-2-R-3, dan SL1-2-R-4) yang mendegradasi xylan 0,5 hingga suhu 60 C dipilih sebagai isolat potensial. Tiga isolat potensial dan type strain NBRC 105837 dapat mendegradasi substrat Remazol Brilliant Blue R-xylan (RBB-xylan) 0,1 pada medium Mm padat setelah 3 hari inkubasi pada suhu 45 hingga 60 C. Tiga isolat potensial telah diidentifikasi pada penelitian sebelumnya sebagai Actinomadura keratinilytica berdasarkan karakter genotip dan fenotip. Crude enzyme dari tiga isolat potensial dan type strain NBRC 105837 dapat mendegradasi xylan 0,5 dan RBB-xylan 0,1 pada medium Mm padat setelah 24 jam inkubasi pada suhu 45 hingga 60 C. Berdasarkan analisis filogenetik sequence gen 16S rRNA menggunakan metode neighbor-joining, minimum evolution, dan maximum likelihood, 3 isolat potensial membentuk clade yang monofiletik dengan dua spesies Actinomadura termofilik yang dapat mendegradasi xylan (A. keratinilytica dan A. miaoliensis). Tiga isolat potensial membentuk clade yang monofiletik dengan empat spesies Actinomadura termofilik (A. keratinilytica, A. miaoliensis, A. rubrobrunea, dan A. viridilutea). Tiga isolat potensial menghasilkan miselium substrat yang bercabang dan tidak berfragmen, serta miselium aerial yang menghasilkan spora pada medium modified Bennetts padat setelah 14 hari inkubasi pada suhu 45 C. Penelitian ini memberikan informasi tambahan mengenai kemampuan typestrain A. keratinilytica NBRC 105837 mendegradasi xylan.

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The aims of this study were to obtain the potential xylan-degrading thermophilic Actinobacteria isolates from soil of Cisolok geysers and to understand their relationship with the closely related taxa of xylanase-producing Actinobacteria. Seventeen thermophilic Actinobacteria isolates were isolated from soil collected around Cisolok geysers, West Java. Xylan-degrading ability of 17 Actinobacteria isolates and type strain Actinomadura keratinilytica NBRC 105837T were screened by using Minimal (Mm) agar medium with the addition of 0.5 xylan substrate, incubated for 7 days. Clear zone was formed around the colony of Actinobacteria isolates which showed xylan-degrading ability at 45 C (15 isolates), 50 C (14 isolates), 55 C (4 isolates), and 60 C (3 isolates) after staining by 0.2 (w/v) Congo red. Type strain NBRC 105837T was able to degrade 0,5 xylan at 45 to 60 C. Three isolates (SL1-2-R-2, SL1-2-R-3, dan SL1-2-R-4) that showed xylan-degrading ability at 45 to 60 C were choosen as potential isolates. Three potential isolates and type strain NBRC 105837T were able to degrade 0,1 Remazol Brilliant Blue R-xylan (RBB-xylan) substrate on Mm agar after 3 days incubation at 45 to 60 C. In the previous study, these potential isolates were identified as Actinomadura keratinilytica based on genotypic and phenotypic characters. Crude enzyme of 3 potential isolates and type strain NBRC 105837T were able to degrade both 0.5 xylan and 0.1 RBB-xylan on Mm agar after 24 hours at 45 to 60 C. Phylogenetic analyses based on 16S rRNA gene using neighbor-joining, minimum evolution, and maximum likelihood methods showed the 3 potential isolates formed monophyletic clade with two thermophilic xylan-degrading Actinobacteria species (A. keratinilytica and A. miaoliensis). Three potential isolates formed monophyletic clade with four thermophilic Actinobacteria species (A. keratinilytica, A. miaoliensis, A. rubrobrunea, and A. viridilutea). These isolates produced non-fragmented branched substrate mycelia and spores produced from aerial mycelia after 14 days incubation at 45 C. This study reports a new information regarding the xylan-degrading ability of A. keratinilytica NBRC 105837.

Abstrak :
Tujuan dari penelitian ini adalah untuk memperoleh isolat 'Actinobacteria' termofilik dari tanah di sekitar geiser Cisolok, Jawa Barat yang memiliki aktivitas selulolitik pada suhu tinggi serta mengetahui posisi filogenetik isolat terpilih terhadap spesies-spesies terdekatnya berdasarkan gen 16S rRNA. Penapisan kemampuan degradasi selulosa 17 isolat dilakukan secara kualitatif pada 'Minimal medium' (Mm) padat yang ditambahkan substrat yaitu 'carboxymethyl cellulose' (CMC) 1% (b/v) atau  'microcrystalline cellulose' (MCC) 1% (b/v) kemudian diinkubasi selama 7 hari. Pengamatan dilakukan dengan pewarnaan 'Congo red' 0,2% (b/v) dan zona bening pada sekitar koloni mengindikasikan degradasi substrat. Hasil penapisan menunjukkan bahwa 15 isolat mendegradasi CMC 1% dan 12 isolat mendegradasi MCC 1% pada suhu 45 ^oC, 14 isolat mendegradasi CMC 1% dan MCC 1% pada suhu 50 ^oC, 4 isolat mendegradasi CMC 1% dan MCC 1% pada suhu 55 ^oC, dan 3 isolat mendegradasi CMC 1% dan MCC 1% pada suhu 60 ^oC. Tiga isolat (SL1-2-R-2, SL1-2-R-3, dan SL1-2-R-4) yang mendegradasi CMC 1% dan MCC 1% hingga 60 ^oC merupakan isolat terpilih. Identifikasi dan karakterisasi telah dilakukan pada penelitian sebelumnya dan melaporkan tiga isolat terpilih memiliki kekerabatan terdekat dengan 'Actinomadura keratinilytica' WCC-2665^T(=NBRC 105837^T). Hasil pengujian menunjukkan 'type strain' NBRC 105837^T mendegradasi CMC 1% dan MCC 1% pada medium Mm padat dengan suhu 45, 50, 55, dan 60 ^oC setelah inkubasi 7 hari. 'Crude enzyme' dari tiga isolat potensial dan 'type strain' NBRC 105837^T menunjukkan aktivitas selulolitik pada medium Mm padat yang ditambahkan CMC 1% atau MCC 1% pada suhu 45, 50, 55, dan 60 ^oC. Analisis filogenetik tiga isolat terpilih berdasarkan gen 16S rRNA menggunakan metode 'Neighbor-Joining' (NJ), 'Minimum Evolution' (ME), dan 'Maximum Likelihood' (ML) menunjukkan bahwa tiga isolat terpilih berada pada satu 'clade' monofiletik dengan 'Actinomadura' 'keratinilytica' WCC-2665^T. Analisis filogenetik juga menunjukkan dua kelompok yang terpisah berdasarkan kemampuan menghasilkan selulase pada anggota famili 'Thermomonosporaceae'. ...... The aims of this study were to obtained thermophilic 'Actinobacteria' isolates from soil around Cisolok geyser, West Java with the ability to degrade cellulose at high temperatures and to analyze the phylogenetic position based on 16S rRNA gene of the selected isolates compared to closely related species. Cellulose degradation screening was performed on Minimal (Mm) medium with the addition of 1% (w/v) carboxymethyl cellulose (CMC) or 1% (w/v) microcrystalline cellulose (MCC) as substrate then incubated for 7 days. Cellulose degradations were observed by staining the plates with  0,2% (w/v) Congo red and clear zone formation around the bacterial colony would indicate the cellulose degradation. The results showed that 15 isolates were able to degrade 1% CMC and 12 isolates were able to degrade 1% MCC at 45 ^oC, 14 isolates were able to degrade 1% CMC and 1% MCC at 50 ^oC, 4 isolates were able to degrade 1% CMC and 1% MCC at 55 ^oC, and 3 isolates were able to degrade 1% CMC and 1% MCC at 60 ^oC. Three isolates (SL1-2-R-2, SL1-2-R-3, and SL1-2-R-4) were selected due to their CMC and MCC degrading ability at 60 ^oC. Molecular identification based on 16S rRNA gene and characterization in previous study showed that the three selected isolates are closely related to 'Actinomadura keratinilytica' WCC-2665^T(=NBRC 105837^T). The assay showed that type strain NBRC 105837^T was able to degrade 1% CMC and 1% MCC at 45, 50, 55, and 60 ^oC after 7 days of incubation. Cellulolytic activity show that the crude enzymes of the three selected isolates and type strain were able to degrade 1% CMC and 1% MCC at 45, 50, 55, and 60 ^oC. Phylogenetic analysis using Neighbour-Joining (NJ), Minimum Evolution (ME), and Maximum Likelihood (ML) methods showed that the  three selected isolates  were  clustered  together in monophyletic clade with 'Actinomadura keratinilytica' WCC-2265^T with 100% bootstrap value. Phylogenetic analysis also showed that cellulase  producers  and  non-cellulase  producers  in 'Thermomonosporaceae' were grouped into different clades.

Abstrak :
Penelitian ini bertujuan untuk memperoleh informasi mengenai pengaruh variasi medium pertumbuhan terhadap pembentukan miselium aerial dan aktivitas antimikroba delapan isolat rare Actinobacteria termofilik dari tanah di sekitar geiser Cisolok, Jawa Barat. Pengujian pertumbuhan, pembentukan miselium aerial, dan aktivitas antimikroba dilakukan dengan menumbuhkan isolat pada medium ISP 1 agar, ISP 1 gellan gum, ISP 2 agar, ISP 2 gellan gum, ISP 3 agar, ISP 3 gellan gum, Bennett’s agar, Bennett’s gellan gum, Minimal (Mm) 3 agar, Mm 3 gellan gum, 2% agar, dan 2% gellan gum. Isolat kemudian diinkubasi pada suhu 45 °C selama 7 dan 14 hari. Konfirmasi suhu pertumbuhan menunjukkan 2 isolat dapat tumbuh hingga suhu 45 °C dan 6 isolat dapat tumbuh hingga 50 °C. Hasil pengujian variasi medium pertumbuhan menunjukkan semua isolat rare Actinobacteria dapat menghasilkan miselium substrat pada semua medium. Hasil pengamatan setelah inkubasi selama 7 hari pada suhu inkubasi 45 °C menunjukkan isolat-isolat tersebut dapat menghasilkan miselium aerial pada medium ISP 1 agar (2 isolat), Mm 3 agar (3 isolat), 2% agar (5 isolat), dan 2% gellan gum (5 isolat). Hasil pengamatan setelah inkubasi selama 14 hari menunjukkan isolat-isolat tersebut dapat menghasilkan miselium aerial pada medium ISP 1 gellan gum (2 isolat), ISP 2 agar (1 isolat), ISP 2 gellan gum (3 isolat), ISP 3 agar dan gellan gum (2 isolat), Mm 3 agar 3 isolat, dan Mm 3 gellan gum (3 isolat). Hasil pengujian aktivitas antibakteri menunjukkan isolat SL3-2-R-11 yang ditumbuhkan pada medium ISP 3 gellan gum dan SL3-1-R-7 yang ditumbuhkan pada Bennett’s agar selama 7 hari dapat menghambat pertumbuhan Staphylococcus aureus. Hasil pengujian aktivitas antikhamir menunjukkan isolat SL3-2- R-11 yang ditumbuhkan pada medium ISP 3 gellan gum dan SL3-1-R-7 pada medium Bennett’s agar selama 14 hari dapat menghambat pertumbuhan Candida albicans. Hasil pengujian aktivitas antifungi menunjukkan tidak ada isolat yang dapat menghambat pertumbuhan Aspergillus flavus.

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This study aims to obtain information about the effect of growth medium variations on the formation of aerial mycelium and antimicrobial activity of eight thermophilic rare Actinobacteria isolates from the soil around Cisolok geyser, West Java. The ability to grow at various media, aerial mycelium formation, and antimicrobial activity were carried out by growing isolates on medium ISP 1 agar, ISP 1 gellan gum, ISP 2 agar, ISP 2 gellan gum, ISP 3 agar, ISP 3 gellan gum, Bennett’s agar, Bennett’s gellan gum, Minimum (Mm) 3 agar, Mm 3 gellan gum, 2% agar, and 2% gellan gum. The isolates were then incubated at 45 oC for 7 and 14 days. Growth test at various temperatures showed that two isolates could grow at a temperature of 45 oC and six isolates could grow up to 50 oC. The results of the growth medium variation test showed that all rare Actinobacteria isolates could produce substrate mycelium in all mediums. Observations after incubation for 7 days at 45 °C showed that these isolates could produce aerial mycelium on ISP 1 agar medium (2 isolates), Mm 3 agar (3 isolates), 2% agar (5 isolates), and 2% gellan gum (5 isolates). Observations after incubation for 14 days showed that these isolates could produce aerial mycelium on the medium ISP 1 gellan gum (2 isolates), ISP 2 agar (1 isolate), ISP 2 gellan gum (3 isolates), ISP 3 agar and gellan gum (2 isolates), Mm 3 agar 3 isolates, and Mm 3 gellan gum (3 isolates). The results of antibacterial activity test showed that isolates SL3-2-R-11 grown on ISP 3 gellan gum and SL3-1-R-7 grown on Bennett’s agar for 7 days could inhibit the growth of Staphylococcus aureus. The antifungal activity test of isolates SL3-2-R-11 grown on ISP 3 gellan gum medium and SL3-1-R-7 on Bennett’s agar for 14 days showed inhibition towards Candida albicans. Meanwhile, all isolates did not show antifungal activity against Aspergillus flavus

Abstrak :
The aims of this study are to provide data regarding the taxonomic study of thermophilic Actinobacteria based on 16S rRNA gene sequences, description, and assessment for secondary metabolite biosynthetic gene clusters (BGCs) in the genome of novel taxa, and its antibacterial activity. Thirty-one isolates of thermophilic Actinobacteria were isolated from soil samples in Cisolok geothermal area, West Java. The 16S rRNA gene sequence-similarity search against all related species was performed using EzTaxon-e database. The sequences of 31 isolates showed similarity to member of family Micromonosporaceae, Nocardiaceae, Pseudonocardiaceae, Streptomycetaceae, Streptosporangiaceae, and Thermomonosporaceae. Six isolates displayed high similarity to genera in the family Pseudonocardiaceae, and most closely related to the genus Thermotunica, T. guangxiensis AG2-7T with similarity values from 94.6 to 95.2%. Phenotypic features and phylogenetic data differentiated strain SL3-2-4T from members of the family Pseudonocardiaceae. Therefore, the strain SL3-2-4T is proposed as a representative of a novel species in a novel genus, Gandjariella thermophila gen. nov., sp. nov. The genome of SL3-2-4T contained 21 antiSMASH-identified secondary metabolite regions harboring BGCs. These BGCs were for polyketide synthase, non-ribosomal peptide synthase, and ribosomally synthesized and post-translationally modified peptide family clusters. Thirteen and five regions displayed low (4–35%) and no similarity with known BGCs for secondary metabolites, respectively. Screening for antibacterial activity showed that strains SL3-2-4T and SL3-2-7 on MM 2 medium solidified with gellan gum at 45°C for 14 days demonstrated inhibitory activity against all Gram-positive, but not Gram-negative bacteria. Strain SL3-2-10 on ISP 3 gellan gum medium incubated for seven-days only active against K. rhizophila NBRC 12078. The results indicated that novel taxa have the potential for the discovery of active secondary metabolites.

Abstrak :
Tujuan penelitian adalah mengetahui aktivitas amilolitik 17 isolat Actinobacteria termofilik pada suhu tinggi, dan memperoleh informasi spesies, dan posisi filogenetik isolat potensial berdasarkan data sekuens gen 16S rRNA, analisis filogenetik, karakterisasi morfologi, fisiologi, dan biokimia. Kemampuan tumbuh 17 isolat Actinobacteria termofilik pada berbagai variasi suhu diuji menggunakan medium ISP 1 agar, dan diinkubasi pada suhu 45, 50, 55, 60 °C selama 7 hari. Berdasarkan hasil penelitian, 17 isolat memiliki pertumbuhan yang bervariasi pada suhu 45-60 °C. Tujuh belas isolat tumbuh pada suhu inkubasi 45 °C, 16 isolat pada suhu 50 °C, enam isolat pada suhu 55 °C, dan lima isolat pada suhu 60 °C terdiri atas SL1-2-R-2, SL1-2-R-3, SL1-2-R-4, SL2-2-R-15, dan SL3-1-R-16. Aktivitas amilolitik 17 isolat Actinobacteria termofilik pada berbagai variasi suhu diuji dengan metode starch agar plate, menggunakan medium Minimal (Mm) agar dengan penambahan pati (soluble starch) sebagai substrat sebanyak 1% (b/v), dan diinkubasi pada suhu 45, 50, 55, dan 60 °C selama 7 hari. Aktivitas amilolitik yang positif ditandai dengan terbentuknya zona bening di sekitar koloni bakteri setelah diteteskan larutan Lugol's iodine sebanyak 1,5 ml. Hasil penelitian menunjukkan bahwa sebagian besar isolat yang diperoleh dari tanah di dekat geiser Cisolok memiliki aktivitas amilolitik yang bervariasi pada suhu 45-60 °C. Lima belas isolat memiliki aktivitas amilolitik pada suhu 45 °C, 13 isolat pada suhu 50 °C, empat isolat pada suhu 55 °C, dan hanya tiga isolat pada suhu 60 °C. Namun demikian, dua isolat (SL2-2-R-15 dan SL3-1-R-16) tidak memiliki aktivitas amilolitik pada suhu 45, 50, dan 55 °C setelah diinkubasi selama 7 hari. Tiga isolat potensial yang memiliki aktivitas amilolitik pada suhu 60 °C (SL1-2-R-2, SL1-2-R-3, dan SL1-2-R-4), berdasarkan data sekuens gen 16S rRNA, analisis filogenetik, dan karakterisasi fenotipik tiga isolat potensial tersebut diidentifikasi sebagai Actinomadura keratinilytica. ......The aims of this study were to screen for amylolytic activity of the 17 themorphilic Actinobacteria at high temperature, and to obtain species information and phylogenetic position based on 16S rRNA gene sequence, phylogenetic analysis, morphological, physiological, and biochemical characterizations. The ability to grow at various temperature was carried out on ISP 1 agar medium, incubated at 45, 50, 55, 60 °C for 7 days. The results showed that the 17 isolates Actinobacteria have varying growth at a temperature of 45-60 °C. Seventeen, 16, and six isolates grew at 45, 50, and 55 °C, respectively, and only five isolates grew at 60 °C, designated SL1-2-R-2, SL1-2-R-3, SL1-2-R-4, SL2-2-R-15, and SL3-1-R-16. Amylolytic activity of the 17 themorphilic Actinobacteria at various temperature was carried out using the starch agar plate method on Minimal (Mm) agar medium with the addition of 1% (w/v) soluble starch as substrate, and incubated at 45, 50, 55, and 60 °C for up to 7 days. Amylolytic activity was detected by flooding the plates with 1.5 ml of Lugol's iodine solution. Clear zones around the colonies indicated positive results for amylolytic activity. The results showed that most of the isolates obtained from the soil near the Cisolok geyser have varying amylolytic activity at a temperature of 45-60 °C. In this study, 15, 13, four, and three out of 17 isolates were positive for amylolytic activity at 45, 50, 55, and 60 °C, respectively. Meanwhile, two isolates, designated SL2-2-R-15 and SL3-1-R-16, showed negative results for amylolytic activity at 45, 50, and 55 °C, even after 7 days of incubation. Three potential isolates which have amylolytic activity at 60 °C (designated SL1-2-R-2, SL1-2-R-3, and SL1-2-R-4), based on 16S rRNA gene sequence, phylogenetic analysis, and phenotypic characterizations were identified as Actinomadura keratinilytica.

Abstrak :
Kelompok Actinobacteria berfilamen merupakan bakteri Gram positif yang beberapa anggotanya diketahui memiliki kemampuan mendegradasi selulosa dengan menghasilkan selulase. Penelitian ini bertujuan untuk mengetahui kemampuan tumbuh isolat Actinobacteria-like GL1-2, GL1-9, dan GL1-12 pada variasi media agar (ISP 1, ISP 2, ISP 3, dan modified Bennett’s) dan suhu (25, 30, 35, 40, 45, 50, dan 55°C), serta mengetahui kemampuan selulolitiknya pada substrat 1% CMC di berbagai suhu (30, 35, 40, 45, 50, dan 55°C). Kemampuan selulolitik diuji dengan menginokulasi biakan pada medium agar minimal (Mm) dengan penambahan 1% CMC, kemudian diinkubasi pada berbagai suhu selama 3, 7, dan 14 hari. Kemampuan selulolitik diamati dengan terbentuknya zona bening di sekitar koloni setelah ditetesi 0,1% Congo red dan dibilas dengan larutan NaCl 1 M. Isolat GL1-2 dan GL1-9 menunjukkan pertumbuhan miselium substrat dalam jumlah banyak pada semua medium yang diuji, namun sporulasi penuh hanya teramati pada medium ISP 1 agar dan MBA. Isolat GL1-12 menunjukkan pertumbuhan miselium substrat yang baik kecuali pada medium ISP 2 agar, namun sporulasi hanya teramati pada medium ISP 3 agar. Suhu pertumbuhan isolat GL1-2 dan GL1-9 berkisar antara 30--55°C, sedangkan GL1-12 berkisar antara 35--55°C. Hasil uji kemampuan selulolitik menunjukkan bahwa isolat GL1-2 dan GL19 memiliki kemampuan mendegradasi 1% CMC pada suhu 30, 35, 40, 45, 50, dan 55°C. Isolat GL1-12 memiliki kemampuan selulolitik pada suhu 40, 45, 50, dan 55°C. Hasil penelitian menunjukkan bahwa ketiga isolat Actinobacteria-like dari serasah di kawasan sumber air panas gunung Galunggung memiliki potensi menghasilkan enzim selulase di berbagai suhu yang diuji. ......Members of Gram-positive filamentous Actinobacteria are some recognized for their ability to degrade cellulose by producing cellulase. This study aimed to determine the growth ability of three Actinobacteria-like isolates (designated isolates GL1-2, GL19, and GL1-12) obtained from litter samples of mount Galunggung hot spring, Tasikmalaya, West Java, on various agar media (ISP 1, ISP 2, ISP 3, and modified Bennett’s) and temperatures (25, 30, 35, 40, 45, 50, 55°C), along with their cellulolytic ability on 1% carboxymethyl cellulose (CMC) as substrate. Cellulolytic ability was tested by inoculating the cultures on minimal (Mm) agar plates with the addition of 1% CMC, and incubated at various temperatures (30, 35, 40, 45, 50, and 55°C) for 3, 7, and 14-days. Cellulolytic ability was observed as formation of clear zone surrounding the colonies after being flooded with 0.1% Congo red and rinsed with 1 M NaCl solution. The results showed that isolates GL1-2 and GL1-9 have abundant substrate mycelia formation on all media tested, while optimal sporulation was only observed on ISP 1 agar and MBA. Isolate GL1-12 showed good growth of substrate mycelia except on ISP 2 agar, however sporulation was poorly observed only on ISP 3 agar. Growth temperatures of isolates GL1-2 and GL1-9 were ranging from 30 to 55°C, while GL112 was ranging from 35 to 55°C. Isolates GL1-2 and GL1-9 have the ability to degrade 1% CMC at 30, 35, 40, 45, 50, and 55°C. Isolate GL1-12 has celulolytic ability at temperatures of 40, 45, 50, and 55°C. This study revealed that Actinobacteria-like isolates obtained from litter samples of mount Galunggung hot spring, Tasikmalaya are potential cellulase-producers on various tested temperatures.

Abstrak :
Tujuan penelitian adalah mengetahui aktivitas amilolitik 17 isolat 'Actinobacteria' termofilik pada suhu tinggi, dan memperoleh informasi spesies, dan posisi filogenetik isolat potensial berdasarkan data sekuens gen 16S rRNA, analisis filogenetik, karakterisasi morfologi, fisiologi, dan biokimia. Kemampuan tumbuh 17 isolat 'Actinobacteria' termofilik pada berbagai variasi suhu diuji menggunakan medium ISP 1 agar, dan diinkubasi pada suhu 45, 50, 55, 60 ^oC selama 7 hari. Berdasarkan hasil penelitian, 17 isolat memiliki pertumbuhan yang bervariasi pada suhu 45--60 ^oC. Tujuh belas isolat tumbuh pada suhu inkubasi 45 ^oC, 16 isolat pada suhu 50 ^oC, enam isolat pada suhu 55 ^oC, dan lima isolat pada suhu 60 ^oC terdiri atas SL1-2-R-2, SL1-2-R-3, SL1-2-R-4, SL2-2-R-15, dan SL3-1-R-16. Aktivitas amilolitik 17 isolat 'Actinobacteria' termofilik pada berbagai variasi suhu diuji dengan metode 'starch agar plate', menggunakan medium Minimal (Mm) agar dengan penambahan pati ('soluble starch') sebagai substrat sebanyak 1% (b/v), dan diinkubasi pada suhu 45, 50, 55, dan 60 ^oC selama 7 hari. Aktivitas amilolitik yang positif ditandai dengan terbentuknya zona bening di sekitar koloni bakteri setelah diteteskan larutan 'Lugol's iodine' sebanyak 1,5 ml. Hasil penelitian menunjukkan bahwa sebagian besar isolat yang diperoleh dari tanah di dekat geiser Cisolok memiliki aktivitas amilolitik yang bervariasi pada suhu 45--60 ^oC. Lima belas isolat memiliki aktivitas amilolitik pada suhu 45 ^oC, 13 isolat pada suhu 50 ^oC, empat isolat pada suhu 55 ^oC, dan hanya tiga isolat pada suhu 60 ^oC. Namun demikian, dua isolat (SL2-2-R-15 dan SL3-1-R-16) tidak memiliki aktivitas amilolitik pada suhu 45, 50, dan 55 ^oC setelah diinkubasi selama 7 hari. Tiga isolat potensial yang memiliki aktivitas amilolitik pada suhu 60 ^oC (SL1-2-R-2, SL1-2-R-3, dan SL1-2-R-4), berdasarkan data sekuens gen 16S rRNA, analisis filogenetik, dan karakterisasi fenotipik tiga isolat potensial tersebut diidentifikasi sebagai 'Actinomadura keratinilytica'. ...... The aims of this study were to screen for amylolytic activity of the 17 themorphilic 'Actinobacteria' at high temperature, and to obtain species information and phylogenetic position based on 16S rRNA gene sequence, phylogenetic analysis, morphological, physiological, and biochemical characterizations. The ability to grow at various temperature was carried out on ISP 1 agar medium, incubated at 45, 50, 55, 60 ^oC for 7 days. The results showed that the 17 isolates 'Actinobacteria' have varying growth at a temperature of 45--60 ^oC. Seventeen, 16, and six isolates grew at 45, 50, and 55 ^oC, respectively, and only five isolates grew at 60 ^oC, designated SL1-2-R-2, SL1-2-R-3, SL1-2-R-4, SL2-2-R-15, and SL3-1-R-16. Amylolytic activity of the 17 themorphilic 'Actinobacteria' at various temperature was carried out using the starch agar plate method on Minimal (Mm) agar medium with the addition of 1% (w/v) soluble starch as substrate, and incubated at 45, 50, 55, and 60 ^oC for up to 7 days. Amylolytic activity was detected by flooding the plates with 1.5 ml of Lugol's iodine solution. Clear zones around the colonies indicated positive results for amylolytic activity. The results showed that most of the isolates obtained from the soil near the Cisolok geyser have varying amylolytic activity at a temperature of 45--60° C. In this study, 15, 13, four, and three out of 17 isolates were positive for amylolytic activity at 45, 50, 55, and 60 ^oC, respectively. Meanwhile, two isolates, designated SL2-2-R-15 and SL3-1-R-16, showed negative results for amylolytic activity at 45, 50, and 55 ^oC, even after 7 days of incubation. Three potential isolates which have amylolytic activity at 60 ^oC (designated SL1-2-R-2, SL1-2-R-3, and SL1-2-R-4), based on 16S rRNA gene sequence, phylogenetic analysis, and phenotypic characterizations were identified as 'Actinomadura keratinilytica.'