Teixeira Januana S, Seeras Arisha, Sanchez-Maldonado Alma Fernanda, Zhang Chonggang, Su Marcia Shu-Wei, Gänzle Michael G
Department of Agricultural, Food and Nutritional Science, University of Alberta, 4-10 Ag/For, Edmonton, AB, Canada T6G 2P5.
Department of Agricultural, Food and Nutritional Science, University of Alberta, 4-10 Ag/For, Edmonton, AB, Canada T6G 2P5.
Food Microbiol. 2014 Sep;42:172-80. doi: 10.1016/j.fm.2014.03.015. Epub 2014 Mar 29.
This study aimed to determine whether glutamine deamidation improves acid resistance of Lactobacillus reuteri, and to assess whether arginine, glutamine, and glutamate-mediated acid resistance are redundant or complementary mechanisms of acid resistance. Three putative glutaminase genes, gls1, gls2, and gls3, were identified in L. reuteri 100-23. All three genes were expressed during growth in mMRS and wheat sourdough. L. reuteri consistently over-expressed gls3 and the glutamate decarboxylase gadB. L. reuteri 100-23ΔgadB over-expressed gls3 and the arginine deiminase gene adi. Analysis of the survival of L. reuteri in acidic conditions revealed that arginine conversion is effective at pH of 3.5 while glutamine or glutamate conversion were effective at pH of 2.5. Arginine conversion increased the pHin but not ΔΨ; glutamate decarboxylation had only a minor effect on the pHin but increased the ΔΨ. This study demonstrates that glutamine deamidation increases the acid resistance of L. reuteri independent of glutamate decarboxylase activity. Arginine and glutamine/glutamate conversions confer resistance to lactate at pH of 3.5 and phosphate at pH of 2.5, respectively. Knowledge of L. reuteri's acid resistance improves the understanding of the adaptation of L. reuteri to intestinal ecosystems, and facilitates the selection of probiotic and starter cultures.
本研究旨在确定谷氨酰胺脱酰胺作用是否能提高罗伊氏乳杆菌的耐酸性，并评估精氨酸、谷氨酰胺和谷氨酸介导的耐酸性是冗余机制还是互补机制。在罗伊氏乳杆菌100-23中鉴定出三个假定的谷氨酰胺酶基因，即gls1、gls2和gls3。这三个基因在mMRS培养基和小麦酸面团中生长时均有表达。罗伊氏乳杆菌持续过表达gls3和谷氨酸脱羧酶gadB。罗伊氏乳杆菌100-23ΔgadB过表达gls3和精氨酸脱亚氨酶基因adi。对罗伊氏乳杆菌在酸性条件下存活率的分析表明，精氨酸转化在pH 3.5时有效，而谷氨酰胺或谷氨酸转化在pH 2.5时有效。精氨酸转化提高了细胞内pH值，但未改变跨膜电位差（ΔΨ）；谷氨酸脱羧作用对细胞内pH值影响较小，但增加了跨膜电位差。本研究表明，谷氨酰胺脱酰胺作用可独立于谷氨酸脱羧酶活性提高罗伊氏乳杆菌的耐酸性。精氨酸和谷氨酰胺/谷氨酸转化分别在pH 3.5时赋予对乳酸的抗性和在pH 2.5时赋予对磷酸盐的抗性。了解罗伊氏乳杆菌的耐酸性有助于增进对其适应肠道生态系统的理解，并便于益生菌和发酵剂培养物的选择。
