Fontana Alessandra, Falasconi Irene, Molinari Paola, Treu Laura, Basile Arianna, Vezzi Alessandro, Campanaro Stefano, Morelli Lorenzo
Department for Sustainable Food Process - DiSTAS, Università Cattolica del Sacro Cuore, Piacenza, Italy.
Department of Biology, University of Padua, Padua, Italy.
Front Microbiol. 2019 Jun 26;10:1380. doi: 10.3389/fmicb.2019.01380. eCollection 2019.
belongs to the large group of lactic acid bacteria (LAB), which are the major players in the fermentation of a wide range of foods. LAB are also present in the human gut, which has often been exploited as a reservoir of potential novel probiotic strains, but several parameters need to be assessed before establishing their safety and potential use for human consumption. In the present study, six strains isolated from natural whey cultures were analyzed for their phenotype and genotype in exopolysaccharide (EPS) production, low pH and bile salt tolerance, bile salt hydrolase (BSH) activity, and antibiotic resistance profile. In addition, a comparative genomic investigation was performed between the six newly sequenced strains and the 51 publicly available genomes of to define the pangenome structure. The results indicate that the newly sequenced strain UC1267 and the deposited strain DSM 20075 can be considered good candidates for gut-adapted strains due to their ability to survive in the presence of 0.2% glycocholic acid (GCA) and 1% taurocholic and taurodeoxycholic acid (TDCA). Moreover, these strains had the highest bile salt deconjugation activity among the tested strains. Considering the safety profile, none of these strains presented antibiotic resistance phenotypically and/or at the genome level. The pangenome analysis revealed genes specific to the new isolates, such as enzymes related to folate biosynthesis in strains UC1266 and UC1267 and an integrated phage in strain UC1035. Finally, the presence of maltose-degrading enzymes and multiple copies of 6-phospho-β-glucosidase genes in our strains indicates the capability to metabolize sugars other than lactose, which is related solely to dairy niches.
属于乳酸菌（LAB）这一大类，乳酸菌是多种食品发酵的主要参与者。乳酸菌也存在于人体肠道中，人体肠道常被用作潜在新型益生菌菌株的储存库，但在确定其安全性和对人类消费的潜在用途之前，需要评估几个参数。在本研究中，对从天然乳清培养物中分离出的6株菌株进行了分析，检测其胞外多糖（EPS）产生、低pH和胆盐耐受性、胆盐水解酶（BSH）活性以及抗生素抗性谱的表型和基因型。此外，对6株新测序菌株与51个公开可用的基因组进行了比较基因组研究，以确定泛基因组结构。结果表明，新测序的菌株UC1267和保藏菌株DSM 20075可被视为肠道适应性菌株的良好候选者，因为它们能够在0.2%甘氨胆酸（GCA）以及1%牛磺胆酸和牛磺脱氧胆酸（TDCA）存在的情况下存活。此外，在测试的菌株中，这些菌株具有最高的胆盐去结合活性。考虑到安全性，这些菌株在表型和/或基因组水平上均未表现出抗生素抗性。泛基因组分析揭示了新分离株特有的基因，例如菌株UC1266和UC1267中与叶酸生物合成相关的酶以及菌株UC1035中的一个整合噬菌体。最后，我们的菌株中存在麦芽糖降解酶和多个6-磷酸-β-葡萄糖苷酶基因拷贝，这表明它们具有代谢除乳糖以外的糖类的能力，而乳糖代谢仅与乳制品生态位相关。
