Schwab Clarissa, Walter Jens, Tannock Gerald W, Vogel Rudi F, Gänzle Michael G
Department Agricultural Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
Syst Appl Microbiol. 2007 Sep;30(6):433-43. doi: 10.1016/j.syapm.2007.03.007. Epub 2007 May 8.
Glycosyltransferases of lactic acid bacteria are associated with biofilm formation, bacterial stress response and sucrose metabolism. The aim of this study was to determine the contribution of glycosyltransferases to sucrose metabolism in Lactobacillus reuteri TMW1.106 expressing the glucosyltransferase GtfA and the inulosucrase Inu, and L. reuteri LTH 5448 expressing the fructosyltransferase FtfA. Transcriptional analysis using quantitative real time PCR revealed that expression of ftfA of L. reuteri LTH5448 was induced by sucrose, while sucrose had no effect on gtfA and inu expression of strain TMW 1.106. Inactivation of ftfA had no influence on growth of L. reuteri LTH5448 and only a minor impact on sucrose turnover. L. reuteri TMW1.106 and its gtfA and inu mutants reached similar cell counts when maltose was offered as substrate. Mutation of gtfA or inu impaired growth in media containing sucrose as sole carbon source despite the expression of sucrose phosphorylase as an alternative sucrose-hydrolysing enzyme. Moreover, the gtfA and inu mutants formed less lactate and ethanol and tolerated lower lactate levels compared to L. reuteri TMW1.106. The inu mutant constitutively overexpressed GtfA. We show here that the impact of different glycosyltransferases on sucrose metabolism of L. reuteri is strain dependent. In strain L. reuteri TMW 1.106, GtfA accounts for sucrose utilization, metabolism, and growth of the organism. In contrast, FtfA of L. reuteri LTH5448 contributes to sucrose turnover but alternative routes for sucrose metabolism are functional in this strain. Our data thus indicate that these glycosyltransferases affect the competitiveness of some L. reuteri strains in ecosystems where sucrose is present.
乳酸菌的糖基转移酶与生物膜形成、细菌应激反应和蔗糖代谢有关。本研究的目的是确定糖基转移酶对表达葡糖基转移酶GtfA和菊粉蔗糖酶Inu的罗伊氏乳杆菌TMW1.106以及表达果糖基转移酶FtfA的罗伊氏乳杆菌LTH 5448中蔗糖代谢的贡献。使用定量实时PCR进行的转录分析表明，罗伊氏乳杆菌LTH5448的ftfA表达受蔗糖诱导，而蔗糖对菌株TMW 1.106的gtfA和inu表达没有影响。ftfA的失活对罗伊氏乳杆菌LTH5448的生长没有影响，对蔗糖周转只有轻微影响。当以麦芽糖作为底物时，罗伊氏乳杆菌TMW1.106及其gtfA和inu突变体达到相似的细胞数量。尽管表达了蔗糖磷酸化酶作为另一种蔗糖水解酶，但gtfA或inu的突变损害了在以蔗糖作为唯一碳源的培养基中的生长。此外，与罗伊氏乳杆菌TMW1.106相比，gtfA和inu突变体产生的乳酸和乙醇较少，并且能耐受较低的乳酸水平。inu突变体组成型过表达GtfA。我们在此表明，不同糖基转移酶对罗伊氏乳杆菌蔗糖代谢的影响因菌株而异。在罗伊氏乳杆菌TMW 1.106菌株中，GtfA负责该生物体的蔗糖利用、代谢和生长。相比之下，罗伊氏乳杆菌LTH5448的FtfA有助于蔗糖周转，但该菌株中蔗糖代谢的替代途径也起作用。因此，我们的数据表明，这些糖基转移酶影响了某些罗伊氏乳杆菌菌株在存在蔗糖的生态系统中的竞争力。
