The draft genome sequence of Lactobacillus salivarius GJ-24 isolated from the feces of healthy adults was determined. Its properties, including milk fermentation activity and bacteriocin production, suggest its potential uses as a probiotic lactic acid bacterium and start culture for dairy products.Lactobacilli colonize the human gastrointestinal tract as normal flora (1), and they can regulate the intestinal homeostasis by providing several beneficial properties, including pathogen inhibition and immunomodulation (5, 7). As an effective probiotic lactobacillus, the genome sequence of Lactobacillus salivarius GJ-24 isolated from the feces of healthy adults was determined using next-generation sequencing (NGS) technology. Additional studies identified that this strain has a high level of activity in lactic acid production during growth in milk medium, indicating its potential uses as a useful starter culture candidate for dairy products such as yogurt and cheese.The sequence data were obtained using a GS FLX Titanium system (Roche Diagnostics, Branford, CT) with an 8-kb-span paired-end library (380,940 reads, ϳ63.4 Mb) and Illumina GA IIx (San Diego, CA) with 100 bp paired-end information (31,391,624 reads, ϳ2,862.3 Mb). All reads were assembled into 11 contigs using GS Assembler 2.3 (Roche Diagnostics, Branford, CT) and CLC Genomics Workbench 4.5.1 (CLC bio, Denmark), and total coverage over the whole genome reached ϳ1,467-fold. The functional annotation of predicted genes was achieved using a RAST server (2) and in-house comparison with the KEGG (6) and COG (9) databases.The draft genome of L. salivarius GJ-24 includes 1,995,968 bp with a 33.0% GϩC ratio. GJ-24 contains 1,883 protein-and 71 tRNA-encoding genes and 4 rRNA operons, and as in other L. salivarius strains (3), the presence of a megaplasmid which reaches approximately 236 kb is detected.Bacteriocin activity and the responsible genes, homologs of salivaricin ABP-118 in L. salivarius UCC118 (4), have been confirmed in preliminary experiments and genome analysis. In contrast to the situation in other strains, the bacteriocin gene cluster is contained in the phage, and it shows a lower degree of similarity (ϳ80%) than other regions of the genome to its counterparts in other strains. The synteny of bacteriocin gene cluster is conserved, except that the AbpIM bacteriocin immunity protein and bacteriocin precursor are moved to the start of the cluster (4). The spectra and level of bacteriocin activity should be investigated in further studies.Comparative genome analysis with other strains revealed that L. salivarius GJ-24 contains the exclusive dextransucrase responsible for sucrose hydrolysis. Also, two alpha-and one beta-galactosidase were identified which play a role in sugar degradation. GJ-24 lacks several gene clusters, including glucitol/sorbitol and fructose/sorbose phpsphotransferase systems and exopolysaccharide (EPS)-related genes (8), but contains unique cell wall-anchored proteins and glycosyltransferases which may contribute to adherence to th...
As a trial for the development of a new starter culture for yogurt products, more than two hundred lactic acid bacteria strains were isolated from raw milk and healthy human feces. The strains that showed excellent growth and acid production ability in the 10% skim milk media were selected and identified as Lactobacillus casei through the API carbohydrate fermentation pattern and 16S rDNA sequence analysis. L. casei CU2604 was further investigated for its physiological characteristics as a starter culture compared with a commercial strain. The CU2604 strain showed good acid production and growth characteristics in milk, which were comparable to those of the L. casei Shirota strain. Despite the fact that both these strains displayed the same sugar fermenting pattern and PFGE band pattern, and had similar growth characteristic in milk, L. casei CU2604 exhibited different fatty acid composition in the cell wall, showed more tolerance to bile and to pH, and presented better growth inhibition activity against pathogenic bacteria. Based on these results, the L. casei CU2604 strain holds great promise for use as a novel and efficient starter culture in the production of yogurt. Additional studies on the probiotic characteristics of this strain are currently being conducted. Key words:Lactobacillus casei, yogurt starter, probiotics, PFGE, fatty acid composition 서 론 많은 소화관 질환이 장 점막 기능의 변화와 연관이 있 고 probiotic 유산균은 장내 균총의 안정화를 위한 새로운 기능성 식품인 것이 밝혀지면서 (Marteau et al., 1993;Salminen et al., 1996;Sanders, 1995) probiotic 유산균이 함유된 발효유 제품이 주는 건강에 유익한 효과에 대한 관심이 증가하고 있다.Probiotics란 장내미생물 균형을 유지시킴으로써 숙주에 게 이로운 작용을 하는 살아있는 미생물을 의미하며 (Fuller, 1989), 충분한 양을 섭취할 경우 면역-염증반응의 억제 (Cebra, 1999), 항암작용(Fuller and Gibson, 1997), 장내균 총의 안정화, 유당불내증 경감, 콜레스테롤 수치 감소 등 과 같은 수요자에게 유익한 효과를 제공한다고 보고되 었다 (Heenan et al., 2004;Sanders, 1993; Schaafsma, 1996a,b). 효과적인 probiotics는 장관을 통과하며 위산과 담즙산에 견뎌야 하고, 장관 내에 부착력이 있어야 하며 (Mishra and Prasad, 2005), 내열성이 뛰어나고 증식이 빨 라야 한다 (Park et al., 1996).Probiotics로 사용되고 있는 미생물로는 Bifidobacterium, Enterococcus, Lactobacillus가 연구되었는데(Gilliland, 1979) Latobacilli의 섭취는 인체의 병원성균에 대한 저항성을 증 가시키며, 이는 probiotic의 선택적인 증가로 인해 병원성 균에 대한 경쟁력이 증가하는 것과 면역조절효과가 있는 것으로 보고되었다 (Havenaar and Spanhaak, 1994). 또한, lactobacilli의 섭취는 macrophages와 lymphocytes, natural killer cells를 증가시키고 γ-interferon의 생산과 IgA 분비 를 증가시킨다고 보고되었다 (Kaila et al., 1992;Perdigon et al., 1990).
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