제주도 연안 해양에서 분리한 한천분해 미생물 Vibrio sp. S4의 동정 및 내열성 agarase의 생화학적 특성 = Identification of a New Agar-hydrolyzing Bacterium Vibrio sp. S4 from the Seawater of Jeju Island and the Biochemical Characterization of Thermostable Agarose

국문 초록 (Abstract)

대한민국 제주도 연안 해수로부터 agarase를 생산하는 균주 S4를 분리하였다. 균주 S4는 그람-음성의 막대형 세포로 부드러운 베이지색 원형 콜로니를 형성하며, 한 개의 극성 편모를 갖는다. S4 균주는 15-42°C, 0.5-5%(w/v) NaCl, pH 6.0-9.0, 0.5-5%(w/v) NaCl 농도에서 안정된 성장을 보인다. S4균주의 G+C content는 49.93 mol%, 세포내 주요 지방산 (>15%)은 C18:1ω7c, C16:0, Summed feature 3(comprising C16:1ω7c/iso-C15:0 2-OH)이다. 16S rRNA 염기서열, 생화학적 및 분류학정 특징에 기초하여 S4 균주를 Vibrio sp. S4로 명명하였다. 0.1% agar를 첨가한 액체배지에서 S4 균주는 72시간에 세포농도와 agarase 활성이 최대치를 보였다. 반면, agar 를 첨가하지 않은 배양액에서의 agarase 활성은 무시할만한 수준이었으며, 이는 균주의 agarase 유전자 발현이 agar에 의해 유도됨을 시사하고 있다. 균주 S4가 세포외부로 분비하는 총 agarase는 45oC와 pH 7.0에서 최상의 효소 활성을 보였으며, agarose를 분해하여 (neo)agarotetraose 와 (neo)agarohexaose를 생산하였다.

다국어 초록 (Multilingual Abstract)

Agar-hydrolyzing bacteria were isolated from the coastal sea water of Jeju Island. One isolate, designated as S4, was selected for further study. The S4 cells were Gram-negative and rod-shaped with smooth beige surfaces and single polar flagellum. Cells were grown at 15-42°C, 0.5-5% (w/v) NaCl, between pH 6.0 and 9.0, and in media containing 0.5-5% (w/v) NaCl. The G+C content was 49.93 mol%. The major fatty acids (>15%) were C18:1ω7c, C16:0 and Summed feature 3 (comprising C16:1ω7c/iso-C15:0 2-OH). Based on 16S rRNA sequencing and biochemical and chemotaxonomic characteristics, the strain was designated as Vibrio sp. S4. In liquid culture supplemented with 0.1% agar the cell density and agarase activity reached a maximum level in 72 h, while agarase activity in the culture without agar was negligible, implying agarose expression is induced by agar. The optimum pH and temperature for the extracellular crude agarase of S4 were 7.0 and 45°C, respectively. However, it also exhibited 98.6% and 87.6% at 40°C and 50°C, respectively, of the maximum activity seen at 45°C. The crude agarase hydrolyzed agarose into (neo)agarotetraose and (neo)agarohexaose.

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