Characterization of Moderately Thermophilic Bacteria Isolated from Saline Hot Spring in Japan

Abstract

Bacillus aeoliusTwelve strains of moderately thermophilic bacteria were isolated from a saline hot spring (55°C, pH 8.3) located in Odaito, Hokkaido, Japan. All strains showed over 99% sequence similarities in the 16S rRNA gene. However, only eight strains grew well at 55°C and demonstrated detectable activities. The representative strains, BEK6 and BEK11, were chosen from individual phenotypic groups and were further characterized. The nucleotide sequence of the almost full-length 16S rRNAgenes of the representative strains showed 97.1% and 96.6% similarity with and , respectively, indicating that the strains belonged to a novel species of the genus . The cells of both strains were Gram-positive and showed catalase and oxidase activities. The optimal growth temperature and pH of strains BEK6 and BEK11 was approximately 50°C and 7-8, respectively. These strains grew in a medium containing 10% NaCl, in contrast to and that grew in a medium containing maximum of 4-5% NaCl. The strain BEK11 showed relatively strong protease and amylase activities in the presence of 3% NaCl, suggesting the potential industrial uses of these enzymes under saline conditions. Key words: thermophile, hot spring, novel species, Dua belas galur bakteri termofilik telah diisolasi dari sumber air panas berkadar garam tinggi (55°C, pH 8.3) yang terletak di Odaito, Hokkaido, Jepang. Semua galur bakteri menunjukkan lebih dari 99% persamaan sekuens dalam gen rRNA 16S. Hanya delapan galur bakteri yang dapat tumbuh dengan baik pada suhu 55°C dan mempunyai aktivitas -galaktosidase. Dari kelompok fenotipe individu BEK6 dan BEK11 dipilih sebagai perwakilan. Urutan nukleotida 16S rRNA secara parsial dari BEK6 dan BEK11 menunjukkan masing-masing 97.1% dan 96.6% kesamaan dengan dan , menunjukkan bahwa galur tersebut adalah spesies baru dari genus . Kedua bakteri adalah Gram-positif dan mempunyai aktivitas katalase dan oksidase. Suhu pertumbuhan optimal galur BEK6 dan BEK11 ialah sekitar 50°C dan pH 7-8. Berbeda dengan dan yang hanya dapat tumbuh dalam medium yang mengandung NaCl maksimum 4-5%, kedua galur bakteri tersebut dapat tumbuh dalam medium yang mengandung NaCl 10%. Galur BEK11 menunjukkan aktivitas protease dan amilase yang yang relatif tinggi dalam kondisi NaCl 3%, sehingga menjanjikan potensinya sebagai produsen enzim industri.Kata kunci: termofil, sumber air panas, spesies baru, β-galactosidase β

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