台灣地熱區抗輻射 Rubrobacter 屬細菌之研究

Abstract

本研究室曾自台灣地熱環境中分離出許多具有輻射線抗性的細菌，其中也包含Rubrobacter 屬的嗜熱菌。Rubrobacter 屬的細菌具有相當強的抗輻射能力，但研究資料卻不多，至今僅有少數Rubrobacter 屬的新菌種被研究與發表。根據 16S rRNA 基因序列分析結果顯示，至今在台灣十個地熱區中總共有32 株屬於Rubrobacter 屬的菌株被分離出。 本研究主要集中於兩群可能屬於Rubrobacter 屬新菌種的六株細菌做詳細的特性分析並加以鑑定。此六株新分離株皆屬於革蘭氏陽性的嗜熱菌，而且都具有抗輻射線的特性。根據遺傳、形態及生理生化特性的分析，顯示第一群來自丹大溫泉的新分離株NTU-806 、 NTU-807 及 NTU-808 為Rubrobacter taiwanensis。而第二群新分離株 NTU-829 、 NTU-1106 、 NTU-1119 與 R. radiotolerans在 16S rRNA 序列相似度為 94 %、DNA-DNA 雜合反應的結果為 26-29 % 間。第二群新分離株的最適生長溫度為 50 ℃ ，最適鹽度為0-7 % ；而標準菌株 R. radiotolerans 則分別為 40 – 50 ℃ 與0-3 % 鹽度之間。此外，相較於R. radiotolerans 而言，第二群的三株分離菌株含有較高含量的 18 碳及19 碳含支鏈飽和脂肪酸。故根據遺傳、形態及生理生化特性等實驗結果，初步鑑定NTU-829 、 NTU-1106 、 NTU-1119 為 Rubrobacter 屬的新菌種。

In the previous studies, several genera of thermophilic bacteria with radiation resistance were isolated from geothermal environments in Taiwan by our laboratory. Though Rubrobacter spp. exhibited extreme radiation resistance, but only a few species had been isolated and studied. According to 16 S rRNA gene sequence analysis, 32 strains of thermophiles belong to genus Rubrobacter were isolated and partially characterized from ten geothermal areas in Taiwan. In this study, we focus on two groups containing six isolates that had the potential to be new species in genus Rubrobacter for further characterization and identification. These new isolates were Gram positive thermophiles with the ability to resist radiation. According to genetic, morphological, physiological and biochemical properties, group 1 isolates NTU-806, NTU-807, and NTU-808 from Danda were identified as R. taiwanensis. Group 2 isolates NTU-829, NTU-1106, and NTU-1119 showed 94 % 16S rRNA gene sequence similarities and 26-29% DNA-DNA similarities to R. radiotolerans. These three isolates grew optimally at 50 oC, and in the medium containing 0-7 % (w/v) NaCl, while R. radiotolerans at 45 oC and 0-3% NaCl. The new isolates from group 2 contained higher amount of 18:0 anteiso and 19:0 anteiso fatty acids than R. radiotolerans. Based on DNA homology, 16S rRNA gene sequence, as well as physiological and biochemical analyses, strains NTU-829, NTU-1106, and NTU-1119 could be identified as a novel species of genus Rubrobacter.