• 한국미생물·생명공학회지
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• 제19권6호
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• pp.619-623
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• 1991

Lactococcus lactis ssp. lactis ML8(L.lactis ML8)의 nisin 생산과 저항 특성을 구명하기 위하여 배지의 종류 및 pH가 nisin의 역가에 미치는 영향, 균체의 생육에 따른 nisin의 생산특성, nisin이 균체생육에 미치는 영향 및 $Ca^[2+}$ 이온의 존재가 균주의 nisin 저항성에 미치는 영향을 조사하였다. Nisin의 역가를 Micrococcus flacus에 대하여 항생효과를 나타내는 성질을 이용하여 agar diffusion법으로 측정하였을 때, M.flavus 생육에 대한 저해직경은 nisin 농도 (0.5`20 unit/ml)의 log치에 비례하였다.

• 한국미생물·생명공학회지
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• 제40권4호
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• pp.310-318
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• 2012

유세포 형광분석에 의한 유산균의 면역증진 효과와 황색포도상구균에 대한 유산균의 항균활성을 확인하여 항아토피 기능성이 있는 유산균을 탐색하고 그 배양법을 검토하였다. T cell에서 CD4+/CD25+/foxp3+ 증가는 Lactobacillus plantarum, Lactococcus lactis subsp. lactis (Lc. lactis)의 순으로 면역증진효과를 보였고, 황색포도상구균에 대한 항균력은 Lc. lactis, Lb. plantarum의 순으로 나타냈다. Lc. lactis 배양액 첨가배지에 Lb. plantarum을 배양한 실험에서는 항균력의 증가가 없었으나 Lb. plantarum 배양액 첨가배지에 Lc. lactis를 배양한 실험에서 황색포도상구균의 항균활성 증대가 나타났다. 항균력을 증가시키는 유산균 첨가배지법의 최적조건은 Lb. plantarum 배양상층액 10%를 첨가하고 가열살균한 배지에서의 Lc. lactis 배양으로 나타났다. 이때 유산균의 항균역가는 Lc. lactis 순수배양 시보다 대수기 말기에 급격히 증가하여, 황색포도상구균의 증식 억제력이 1.29배 높아졌다.

• Journal of Microbiology and Biotechnology
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• 제3권4호
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• pp.217-223
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• 1993

To investigate the nature and location of the nisin-resistance determinant of Lactococcus lactis subsp. lactis 7962 (L. lactis 7962), a total plasmid DNA prepared from L. lactis 7962, a nisin producer, was used to transform L. lactis subsp. lactis LM0230, a plasmid-free and nisin-sensitive strain, by protoplast mediated transformation procedures. All of the nisin-resistant transformants acquired the ability to utilize sucrose at the same time, confirming the close linkage between these two determinants in L. lactis 7962. The plasmid DNA profiles of a few selected nisin-resistant transformants were examined by agarose gel electrophoresis. No common plasmid was found among the transformants and some small plasmids previously not present in L. lactis 7962 were detected. These transformants were named as L. lactis KL1, KL2, KL3, KL4, or KL5, respectively based on their plasmid profiles. Growth curves of all transformants were similar to that of L. lactis LM0230, but different from that of L. lactis 7962. L. lactis KL5 showed the highest level of resistance to nisin, growing up to 1, 200 IU nisin/ml after 40 hr incubation. Some nisin-sensitive derivatives of KL1 or KL2 were obtained by plasmid curing experiments. The plasmid DNA profiles of the nisin-sensitive KL1 derivatives were apparently the same as that of the KL1. All of the nisin-sensitive KL2 derivatives were plasmid-free, but a nisin-resistant strain with no apparent plasmid was also obtained. These results indicate that the nisin-resistance of the $Nis^r$ transformants is presumably mediated by the chromosomally located gene(s) rather than plasmid-encoded gene(s).

• Journal of Microbiology and Biotechnology
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• 제26권11호
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• pp.1829-1835
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• 2016

Dental caries is caused by cariogenic biofilm, an oral biofilm including Streptococcus mutans. Recently, the prevention of dental caries using various probiotics has been attempted. Lactococcus lactis HY 449 is a probiotic bacterium. The aim of this study was to investigate the effect of L. lactis HY 449 on cariogenic biofilm and to analyze its inhibitory mechanisms. Cariogenic biofilm was formed in the presence or absence of L. lactis HY 449 and L. lactis ATCC 19435, and analyzed with a confocal laser microscope. The formation of cariogenic biofilm was reduced in cultures spiked with both L. lactis strains, and L. lactis HY 449 exhibited more inhibitory effects than L. lactis ATCC 19435. In order to analyze and to compare the inhibitory mechanisms, the antibacterial activity of the spent culture medium from both L. lactis strains against S. mutans was investigated, and the expression of glucosyltransferases (gtfs) of S. mutans was then analyzed by real-time RT-PCR. In addition, the sucrose fermentation ability of both L. lactis strains was examined. Both L. lactis strains showed antibacterial activity and inhibited the expression of gtfs, a nd t he d ifference b etween both strains did not show. In the case of sucrose-fermenting ability, L. lactis HY 449 fermented sucrose but L. lactis ATCC 19435 did not. L. lactis HY 449 inhibited the uptake of sucrose and the gtfs expression of S. mutans, whereby the development of cariogenic biofilm may be inhibited. In conclusion, L. lactis HY 449 may be a useful probiotic for the prevention of dental caries.

• 한국미생물·생명공학회지
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• 제26권6호
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• pp.562-565
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• 1998

Nisin-producing and nisin resistant L. lactis subsp. lactis ATCC7962 harbored six plasmids. To find a plasmid containing a nisin resistant gene, these plasmids were transformed into L lactis LM0230 of plasmid-free and nisin sensitive strain. After screening on nisin selection media containing nisin (150 $\mu\textrm{g}$/$m\ell$), several nisin resistant transformants were obtained and the level of nisin resistance was very similar to that of wild type L lactis subsp. lactis ATCC7962. A 26.5 kb plasmid, named as pCS100, which confers resistance to nisin, was identified in transformants. The pCS100 was digested with EcoRI and Southern blot hybridization was done with nisI probe to localize the nisin resistant gene. A 4 kb EcoRI fragment showed a strong positive signal, and it was cloned into pBluescript for the potential selection marker.

• Journal of Pharmaceutical Investigation
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• 제35권2호
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• pp.75-80
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• 2005

A promising application of Lactococcus lactis is its use as live vehicles for production and delivery of heterologous proteins of vaccines and therapeutic substances. Because L. lactis has GRAS ('generally regarded as safe') status, we tested whether L. lactis could function as the carrier of the Ll protein of human papillomavirus (HPV) type 16. The RNA level expression of Ll gene was detected in L. Lactis. The Ll protein was expressed in L. lactis with Ll gene. The growth of strains L. lactis with an empty plasmid (pAMJ328) and L. lactis with Ll-encoding plasmid (pAMJ328-Ll) was slightly decreased in comparison with the growth of strains L. lactis (wild type). However, all the three strains of L. lactis maintained the ability to ferment sugars primarily into lactic acid, indicating that Ll protein did not affect the biochemical property of L. lactis. These results suggest that L. lactis, capable of carrying Ll protein, might be further developed as a biocompatible oral protein delivery system.

• Preventive Nutrition and Food Science
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• 제5권3호
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• pp.153-159
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• 2000

A 4.4 kb DNA fragment encompassing lacA (galactoside acetyltransferase) and lacZ($\beta$-galactosidase) genes from Lactococus lactis ssp. lactis ATCC 7962 (L. lactis 7962) was introduced ito a Lac strain, Lactococcus lactis ssp. lactis MG1363 (L. lactis MG1363) by using a lactococcal expression vector, pMG36e and expression level of lacZ was examined. Growth rates and $\beta$-galactosidase ($\beta$-gal) activities of MG1363 cells carrying recombinant plasmid, pMLZ3, on M17 broth containing different carbon sources (1%, w/v) were examined. Contrary to the expectations, MG1363 [pMLZ3] grown on lactose showed the lowest enzyme activity (17 units) and cells grown on galactose had the highest $\beta$-gal activity (41 units). Cells grown on glucose had intermediate activity (33 units). These activities are about one tenth of the values observed in L. lactis 7962 where lacZ is present as a single-copy gene in the chromosome. When the cellular concentrations of lacZ transcript were examined using slot blot hybridization, it was found that MG1363[pMLZ3] produced sufficient amounts of transcript. These results indicate that either proteolytic degradation of $\beta$-gal or other regulatory mechanism prevent the translation or accumulation of $\beta$-gal in L. lactis MG1363 cells. In regard to regulation, the presence of the ccpA gene in L. lactis MG1363 was confirmed by Southern blot.

• 한국미생물·생명공학회지
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• 제33권4호
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• pp.241-247
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• 2005

선별마커로써 Lactococcus lactis ssp. lactis ATCC 7962 유래의 $\beta$-galactosidase 유전자를 포함하는 Lactococcus용 셔틀/발현 벡터 pWgall3T를 제조하여 Escherichia coli DH5$\alpha$와 고. Lactis MG1363내로 도입하였다. 이들 형질 전환체들은 X-gal을 포함하는 배지에서 파란색의 표현형을 보임으로써 쉽게 확인할 수 있었다. 또한, L. lactis MG1363 형질전환체로부터 $\beta$-galactosidase 활성을 측정한 결과 기존에 $\beta$-galactosidase를 활성을 지닌 L. lactis ATCC 7962에 비해 glucose를 포함하는 M17배지에서 4배정도 높은 활성을 보임으로써 선별마커로써의 효율성을 나타내었다. pWgal13T는 $\beta$-galactosidase 유전자 외에 L. lactis Wg2유래의 replicon과 외래 유전자의 발현을 위한 L. lactis ssp. cremoris LM0230의 promoter P13C, terminator를 포함하고 있다. 이 벡터의 이용가능성을 확인하기 위하여 외래 유전자 EGFP유전자를 P13C 아래에 삽입하여 E. coli와 L. iactis에서 발현을 확인하였다. 이 연구에서 제조된 Lactococcus용 발현 벡터 pWgal13T는 E. coli와 L. lactis에서 외래 유용 유전자를 생산을 위해 이용 할 수 있을 것이다.

• 대한소아치과학회지
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• 제27권4호
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• pp.549-557
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• 2000

치아우식증은 치아구조의 국소적, 침윤적, 분자적인 붕괴로 특징지워지는 치아 경조직에 대한 세균성질환이다. 이런 치아 우식증의 주 원인균인 S. mutans의 치태형성과 증식에 대해 아동의 구강에서 분리된 L. lactis 51의 작용을 연구하여 다음과 같은 결과를 얻었다. 1. 비커 와이어 검사에서 S. mutans와 L. lactis 51의 혼합배양시 S. mutans 단독배양에 비해 치태의 무게가 감소하였다. 2. S. mutans는 S. mutans와 L. lactis 51의 혼합 배양에 비교하여 S. mutans 단독배양시에 생균수가 감소하였다. 3. S. mutans와 L. lactis 51은 M17Y broth에서 단독 및 혼합배양시 배양 12시간 때까지 증가하다가 24시간 때에 감소 하였으나, M17YS broth에서는 S. mutans와 L. lactis 51의 혼합배양시 S. mutans의 생균수가 시간이 지남에 따라 감소하였다. 4. L. lactis 51의 배양 상청액은 S. mutans의 치태형성과 증식에 대해 억제 작용을 하지 못하였다. 5. M17YS broth에서의 L. lactis 51 배양 상청액 성분의 thin layer chromatography에서 자당과 과당이 계속 검출되었다. 이상의 결과를 종합하면 구강에서 분리된 L. lactis 51는 S. mutans의 인공치태 형성과 증식을 억제시키는 것으로 사료된다.

• 대한미생물학회지
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• 제35권1호
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• pp.77-85
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• 2000

Streptococcus mutans is the most important causative bacteria of dental caries among the oral bacteria. Lactococcus lactis 1370 was isolated from the oral cavity of child. The effect of Lactococcus lactis 1370 on the formation of artificial plaque by Streptococcus mutans was studied. 1. The insoluble substances and bacteria were much more attached on the wall of disposable cuvette in the culture of Streptococcus mutans than in the combined culture of Streptococcus mutans and Lactococcus lactis 1370. 2. The mean weight of produced artificial plaque on the wires in the beaker was 131.7 mg in the culture of Streptococcus mutans only, whereas being reduced to 6.4 mg in the combined culture of Streptococcus mutans and Lactococcus lactis 1370 (p<0.05). The viable cell didn't show the significant difference between them after culturing. 3. When Streptococcus mutans was cultured in the media containing culture supernatant of Lactococcus lactis 1370 cultured in M17 broth containing 0.5% yeast extract and 5% sucrose, the mean weight of produced artificial plaque was 8.0 mg on the wires, whereas being 125.4 mg in the media without culture supernatant of Lactococcus lactis 1370 (p<0.05). The viable cell didn't show the significant difference between them after culturing. 4. When Streptococcus mutans was cultured in the media containing soluble polymer produced by Lactococcus lactis 1370, the mean weight of produced artificial plaque was significantly reduced compared with being cultured in the media without soluble polymer (p<0.05). The viable cell didn't show the significant difference between them after culturing. 5. The soluble polymer produced by Lactococcus lactis 1370 was glucan. 6. The glucan produced by Lactococcus lactis 1370 was water-soluble glucan containing ${\alpha}$-1,6-glucose linkage as the main linkage. These results suggest that the artificial plaque formed by Streptococcus mutans is inhibited by water-soluble glucan produced by Lactococcus lactis 1370.