Korean Journal of Microbiology (미생물학회지)

The Microbiological Society of Korea (한국미생물학회)
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Antibacterial Effects of Lactococcus lactis HK-9 Isolated from Feces of a New Born Infant

신생아 태변에서 젖산세균인 Lactococcus lactis HK-9의 분리 및 항균활성

  • Baek, Hyun (Department of Biotechnology, Soonchunhyang University) ;
  • Ahn, Hye-Ran (Department of Biotechnology, Soonchunhyang University) ;
  • Cho, Yun-Seok (Department of Biotechnology, Soonchunhyang University) ;
  • Oh, Kye-Heon (Department of Biotechnology, Soonchunhyang University)
  • 백현 (순천향대학교 생명공학과) ;
  • 안혜란 (순천향대학교 생명공학과) ;
  • 조윤석 (순천향대학교 생명공학과) ;
  • 오계헌 (순천향대학교 생명공학과)
  • Received : 2010.05.12
  • Accepted : 2010.06.05
  • Published : 2010.06.30
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Abstract

The purpose of this work was to investigate the antibacterial activity derived from a lactic acid bacterium, Lactococcus lactis HK-9, isolated from the feces of a 2-day newborn infant. We characterized the physiological and biochemical properties of this strain. Both the BIOLOG system and phylogenetic analysis using 16S rRNA sequencing were utilized for identification, and the strain was assigned to the Lactococcus lactis species, designated as L. lactis HK-9, and registered in GenBank as [GU936712]. We monitored growth rate, production of lactic acid and acetic acid as metabolites, and pH during growth. The maximum concentrations of lactic acid and acetic acid reached 495.6 mM and 104.3 mM, respectively, and the initial pH of the cultures decreased from 7.0 to 4.1 after incubating for 60 h. HPLC was used to confirm the production of lactic acid and acetic acid. Significant antibacterial activity of the concentrated supernatant was demonstrated against Gram-positive (e.g., Staphylococcus aureus, Enterococcus faecalis, Listeria monocytogenes, MRSA) and Gram-negative (e.g., Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Shigella sonnei) bacteria by the plate diffusion method. The antibacterial activity was sensitive to protease, and the molecular weight of the presumed bacteriocin molecule was estimated to be about 4 kDa by tricine-SDS-PAGE.

본 연구는 신생아 태변에서 분리된 Lactococcus lactis HK-9의 다양한 생리적 특성과 항균활성을 조사하기 위하여 실시하였다. 균주 HK-9을 MRS 배지에서 배양하였고, 형태 및 생리학적 특성에 대하여 조사하였으며, BIOLOG 시험과 16SrRNA 염기서열 분석을 통해 균주를 동정하였다. 그 결과 Lactococcus lactis으로 동정되었고, L. lactis HK-9로 명명하였으며, 이 균주의 계통수 분석을 통해 GenBank에 [GU936712]로 등록하였다. 배양기간에 따른 L. lactis HK-9의 생장과 중간 대사산물로서 lactic acid와 acetic acid의 생산 및 pH의 변화를 조사하였으며, 이들 유기산의 생성은 HPLC를 통하여 확인하였다. 유기산의 생성은 L. lactis HK-9의 생장에 따라 증가하는 것을 확인하였으며, 배양 60시간이 지난 후 생성된 lactic acid와 acetic acid의 농도는 각각 495.6 mM, 104.3 mM이었다. 배양 초기의 pH는 7.0이었으며 배양 기간 동안 4.1로 감소하였다. 다양한 그람양성 세균과 그람음성 세균을 대상으로 농축된 HK-9 배양상등액의 항균력을 조사하였으며, 그 결과 항균범위가 그람양성 세균에서만 나타나는 것이 관찰되었다. 농축된 배양상등액을 protease를 처리한 후 항균활성은 소멸하였으며, 상등액의 박테리오신 추정 분자의 분자량은 tricine-SDS-PAGE를 통하여 약 4 kDa으로 확인되었다.

Keywords

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