Lactobacillus casei Low-Temperature, Dairy-Associated Proteome Promotes Persistence in the Mammalian Digestive Tract

We
found that incubation of probiotic Lactobacillus casei BL23 in milk at 4 °C prior to ingestion increased its survival
in the mammalian digestive tract. To investigate the specific molecular
adaptations of L. casei to milk, we used tandem mass
spectrometry to compare proteins produced by L. casei BL23 at 4 °C in milk to those in exponential and stationary
phase cells in laboratory culture medium at either 37 or 4 °C.
These comparisons revealed a core of expressed L. casei proteins as well as proteins produced in either a growth-phase or
temperature-specific manner. In total, 205 L. casei proteins were uniquely expressed or detected in higher abundance
specifically as a result of incubation in milk and included an over-representation
of proteins for cell surface modification, fatty acid metabolism,
amino acid transport and metabolism, and inorganic ion transport.
Genes for DltD (d-alanine transfer protein), FabH (3-oxoacyl-ACP
synthase), RecA (recombinase A), and Sod (superoxide dismutase) were
targeted for inactivation. The competitive fitness of the mutants
was altered in the mouse intestine compared with wild-type cells.
These results show that the food matrix can have a profound influence
on dietary (probiotic) bacteria and their functional significance
in the mammalian gut.

本研究发现，在摄入前于4°C条件下将益生菌乳酸杆菌BL23在牛奶中培养，可显著提高其在哺乳动物消化道的存活率。为探究乳酸杆菌BL23对牛奶的特定分子适应性，本研究采用串联质谱技术，比较了乳酸杆菌BL23在4°C牛奶中产生的蛋白质与在实验室培养介质中处于对数生长期和稳定生长期的细胞在37°C或4°C条件下产生的蛋白质。这些比较揭示了乳酸杆菌BL23表达的核心蛋白质，以及在不同生长阶段或特定温度下产生的蛋白质。总计鉴定出205种乳酸杆菌BL23蛋白，这些蛋白在牛奶中表达独特或含量显著增加，其中富含细胞表面修饰、脂肪酸代谢、氨基酸转运和代谢、以及无机离子转运相关蛋白。针对DltD（d-丙氨酸转移蛋白）、FabH（3-氧酰基-ACP合酶）、RecA（重组酶A）和Sod（超氧化物歧化酶）基因进行敲除，突变株在老鼠肠道中的竞争适应性相较于野生型细胞发生改变。这些结果表明，食物基质对膳食（益生菌）细菌及其在哺乳动物肠道中的功能意义具有深远影响。