Barrangou Rodolphe, Altermann Eric, Hutkins Robert, Cano Raul, Klaenhammer Todd R
Genomic Sciences Program and Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, NC 27695, USA.
Proc Natl Acad Sci U S A. 2003 Jul 22;100(15):8957-62. doi: 10.1073/pnas.1332765100. Epub 2003 Jul 7.
Lactobacillus acidophilus is a probiotic organism that displays the ability to use prebiotic compounds such as fructooligosaccharides (FOS), which stimulate the growth of beneficial commensals in the gastrointestinal tract. However, little is known about the mechanisms and genes involved in FOS utilization by Lactobacillus species. Analysis of the L. acidophilus NCFM genome revealed an msm locus composed of a transcriptional regulator of the LacI family, a four-component ATP-binding cassette (ABC) transport system, a fructosidase, and a sucrose phosphorylase. Transcriptional analysis of this operon demonstrated that gene expression was induced by sucrose and FOS but not by glucose or fructose, suggesting some specificity for nonreadily fermentable sugars. Additionally, expression was repressed by glucose but not by fructose, suggesting catabolite repression via two cre-like sequences identified in the promoter-operator region. Insertional inactivation of the genes encoding the ABC transporter substrate-binding protein and the fructosidase reduced the ability of the mutants to grow on FOS. Comparative analysis of gene architecture within this cluster revealed a high degree of synteny with operons in Streptococcus mutans and Streptococcus pneumoniae. However, the association between a fructosidase and an ABC transporter is unusual and may be specific to L. acidophilus. This is a description of a previously undescribed gene locus involved in transport and catabolism of FOS compounds, which can promote competition of beneficial microorganisms in the human gastrointestinal tract.
嗜酸乳杆菌是一种益生菌，具有利用低聚果糖（FOS）等益生元化合物的能力，这些化合物可刺激胃肠道中有益共生菌的生长。然而，关于乳杆菌属利用FOS的机制和基因，人们了解甚少。对嗜酸乳杆菌NCFM基因组的分析揭示了一个msm基因座，它由一个LacI家族的转录调节因子、一个四组分ATP结合盒（ABC）转运系统、一个果糖苷酶和一个蔗糖磷酸化酶组成。对该操纵子的转录分析表明，基因表达由蔗糖和FOS诱导，但不由葡萄糖或果糖诱导，这表明对难发酵糖具有一定特异性。此外，表达受葡萄糖抑制，但不受果糖抑制，这表明通过在启动子-操纵子区域鉴定出的两个类cre序列进行分解代谢物阻遏。编码ABC转运体底物结合蛋白和果糖苷酶的基因的插入失活降低了突变体在FOS上生长的能力。对该基因簇内基因结构的比较分析表明，与变形链球菌和肺炎链球菌的操纵子具有高度的同线性。然而，果糖苷酶和ABC转运体之间的关联并不常见，可能是嗜酸乳杆菌特有的。这是对一个先前未描述的参与FOS化合物转运和分解代谢的基因座的描述，该基因座可促进人类胃肠道中有益微生物的竞争。
