• 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.

• 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.

• 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.

• 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).

• 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.

• 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.

• Journal of Microbiology and Biotechnology
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• 제2권2호
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• pp.73-77
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• 1992

The effect of a nisin-producing Lactococcus lactis spp. lactis (L. lactis) on the growth and attachment of Listeria monocytogenes Scott A and Brie 1 on stainless steel and their growth in Brain Heart Infusion broth was determined. Viable cells of Listeria decreased rapidly after 9~12 hr of incubation at $21^{\circ}C$ and after 6~9 hr of incubation at $32^{\circ}C$ in the presence of L. lactis. The number of L. monocytogenes Scott A attached to stainless steel in pure culture was $2.5{\times}10^3/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}2.3{\times}10^3/\textrm{cm}^2{\;}at{\;}32^{\circ}C$ after 48 hr of incubation, but was only $10/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}1.1{\times}10/\textrm{cm}^2{\;}at{\;}32^{\circ}C$ in the presence of L. lactis. Results from L. monocytogenes strain Brie 1 were similar to those from strain Scott A. The population of L. monocytogenes Scott A which attached to stainless steel with previously adherent L. lactis was $1.8{\times}10^2/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}8.2{\times}10^2/\textrm{cm}^2{\;}at{\;}32^{\circ}C$, whereas the population attached to sterile stainless steel was $1.2{\times}10^3/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}2.1{\times}10^2/\textrm{cm}^2{\;}at{\;}32^{\circ}C$. For L. monocytogenes Brie 1, the attached population of the control was $1.6{\times}10^4/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}3.2{\times}10^2/\textrm{cm}^2{\;}at{\;}32^{\circ}C$, and on stainless steel with adherent L. lactis, it was $1.1{\times}10/\textrm{cm}^2{\;}at{\;}21^{\circ}C{\;}and{\;}6.9{\times}10/\textrm{cm}^2{\;}at{\;}32^{\circ}C$. Surface adherent L. lactis was less inhibitory to attachment of L. monocytogenes on stainless steel than a liquid culture inoculum. Listeria attached to stainless steel survived dry storage for 20 days both in the presence and absence of adherent lactococci.

• KSBB Journal
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• 제11권4호
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• pp.504-509
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• 1996

Promoters which are useful for constructing expression vectors for lactic acid bacteria were obtained from the chromosomal DNA of Lactococcus lactis ssp. lactis MG1363. pBV5030, a promoter-selection vector, replicates in L. lactis and Escherichia coli and carries a promoterless chloramphenicol acetyltransferase gene (cat-86). After examining E. coli transformants which grew on LB media containing chloramphenicol (Cm, 20$\mu\textrm{g}$/mL) , many MG1363 derived DNA fragments which encompass promoter sequences were identified. Some recombinant E. coli cells can grow at the Cm concentration of 1,000$\mu\textrm{g}$/mL. When plasmids from those highly resistant E. coli cells were purified and introduced into L. lactis ssp. lactis MG1614 cells by electroporation, lactococcal transformants showing Cm resistance were obtained. So far, five plasmids with different promoter inserts were introduced into L. lactis MGl614 cells. The maximum level of Cm resistance in L. lactis MG1614 transformants was quite low (20$\mu\textrm{g}$/mL) when compared with that observed in recombinant E. coli cells harboring the same plasmids.

• Journal of Microbiology and Biotechnology
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• 제9권6호
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• pp.732-736
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• 1999

The superoxide dismutase (SOD) in Lactococcus lactis was measured quantitatively and qualitatively under various culture conditions. The L. lactis SOD was induced by oxidative stress. As the concentration of paraquat to produce superoxide radicals increased, the growth of L. lactis decreased with concomitant increase of SOD activity. The SOD activity was found to be growth-phase dependent: when aerobically grown cells entered to the stationary phase, the activity increased gradually until the late stationary phase. From inhibition studies, L. lactis SOD was found to be insensitive to KCN and $H_2O_2$ which are known to inhibit Cu/ZnSOD and FeSOD, respectively. Moreover, as the concentration of manganese in the medium increased, the activity of SOD also increased. These data strongly suggested that L. lactis possessed a single manganese-containing SOD (MnSOD). Finally, a putative sod gene fragment of 510 bp was identified in L. lactis using a polymerase chain reaction (PCR) with degenerate primers designed from the deduced DNA sequences of known SOD genes.

• 한국식품저장유통학회지
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• 제6권4호
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• pp.442-447
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• 1999

섬유질이 풍부하고 enthocyanin색소가 풍부한 자색 고구마를 이용하기 위하여 탈지유와 설탕이 들어있는 기본배지에 증자, 박피한 고구마를 첨가한 후 5종(Lactebacillus bulgaricis, Lactobacillus delbruchii sub. sp. lactis, Streptococcus lactis, Bifidobacterium bifidum, Leuconostoc lactis) 의 젖산균주를 배양, 접종하여 호상 요쿠르트를 만들고 자색고구마가 젖산균의 생육과산 생성, 색도에 미치는 영향 및 저장성 등을 조사한 결과 L. bulgaricus균을 배양한 경우가 젖산균의 증식과 산 생성이 가장 빨라 발효개시 12시간만에 1.04 $\times$$10^{9}$CFU/$m\ell$의 생균수와 pH 4.22를 나타냈고 B. bifidum균은 발효개시 24시간까지는 젖산균의 증식이 느리게 이루어져 발효개시 36시간에 달할 때 3.3 $\times$ $10^{8}$ CFU/$m\ell$의 생균수와 pH 5.1을 나타냈다. 발효종료 후 자색고구마를 첨가한 요쿠르트의 자색은 B. bifdum균에 의한 요쿠르트제조시 색도가 가장 안정하였고 Leuc. lactis, L. delbruechii sub. sp. lactis, L bulgaricus순으로 안정하였으며 St. lactis균에 의한 요쿠르트는 자색의 색소 소실이 가장 많았다. 2~3$^{\circ}C$에서 저장시 저장 2주까지 pH의 변화는 거의 없었고 생균수의 변화는 L. bulgaricus와 L. delbruechii sub. sp. lactis균에 의해 제조된 요쿠르트는 저장 1주까지는 변화가 없었으나 그 이후는 약간 감소하였으며 St. lactis균과 B. bifidum 균은 저장 1주까지 저온에서도 생균수가 소량 증가함을 보여주었다. 색도는 저장 2주 후 B. bifidum균에 의한 요쿠르트 제조시 자색도가 많이 소실되었고 L. delbruechii sub. sp. lactis균에 의한 요쿠르트가 가장 안정하였다.