Teagasc, Moorepark Food Research Centre, Moorepark, Fermoy, County Cork, Ireland.
Appl Environ Microbiol. 2011 Oct;77(19):6889-98. doi: 10.1128/AEM.05213-11. Epub 2011 Aug 5.
The aim of this study was to investigate the influence of supplementing growth medium with unsaturated fatty acids on the technical properties of the probiotic strain Lactobacillus johnsonii NCC 533, such as heat and acid tolerance, and inhibition of Salmonella enterica serovar Typhimurium infection. Our results showed that the membrane composition and morphology of L. johnsonii NCC 533 were significantly changed by supplementing a minimal Lactobacillus medium with oleic, linoleic, and linolenic acids. The ratio of saturated to unsaturated plus cyclic fatty acids in the bacterial membrane decreased by almost 2-fold when minimal medium was supplemented with unsaturated fatty acids (10 μg/ml). The subsequent acid and heat tolerance of L. johnsonii decreased by 6- and 20-fold when the strain was grown in the presence of linoleic and linolenic acids, respectively, compared with growth in oleic acid (all at 10 μg/ml). Following acid exposure, significantly higher (P < 0.05) oleic acid content was detected in the membrane when growth medium was supplemented with linoleic or linolenic acid, indicating that saturation of the membrane fatty acids occurred during acid stress. Cell integrity was determined in real time during stressed conditions using a fluorescent viability kit in combination with flow cytometric analysis. Following heat shock (at 62.5°C for 5 min), L. johnsonii was unable to form colonies; however, 60% of the bacteria showed no cell integrity loss, which could indicate that the elevated heat inactivated vital processes within the cell, rendering it incapable of replication. Furthermore, L. johnsonii grown in fatty acid-enriched minimal medium had different adhesion properties and caused a 2-fold decrease in S. enterica serovar Typhimurium UK1-lux invasion of HT-29 epithelial cells compared with bacteria grown in minimal medium alone. This could be related to changes in the hydrophobicity and fluidity of the membrane. Our study shows that technical properties underlying probiotic survivability can be affected by nutrient composition of the growth medium.
本研究旨在探讨在基础乳酸菌培养基中添加不饱和脂肪酸对益生菌菌株 Johnson 乳杆菌 NCC 533 的技术特性的影响，如热耐受性、酸耐受性和对肠炎沙门氏菌 Typhimurium 感染的抑制作用。我们的结果表明，通过在最小乳酸菌培养基中添加油酸、亚油酸和亚麻酸，Johnson 乳杆菌 NCC 533 的膜组成和形态发生了显著变化。当最小培养基中添加不饱和脂肪酸（10 μg/ml）时，细菌膜中饱和脂肪酸与不饱和脂肪酸加环脂肪酸的比例几乎降低了 2 倍。当该菌株在亚油酸和亚麻酸存在的情况下生长时，其酸和热耐受性分别比在油酸存在的情况下降低了 6 倍和 20 倍（均为 10 μg/ml）。在酸暴露后，当生长培养基中添加亚油酸或亚麻酸时，膜中检测到的油酸含量显著升高（P < 0.05），表明在酸胁迫下，膜脂肪酸饱和。在应激条件下，使用荧光活细胞试剂盒结合流式细胞术分析实时测定细胞完整性。在经受热冲击（62.5°C 5 分钟）后，Johnson 乳杆菌无法形成菌落；然而，60%的细菌没有细胞完整性损失，这可能表明高温使细胞内的重要过程失活，使其无法复制。此外，在富含脂肪酸的最小培养基中生长的 Johnson 乳杆菌与单独在最小培养基中生长的细菌相比，对 HT-29 上皮细胞的肠炎沙门氏菌 Typhimurium UK1-lux 入侵的黏附特性不同，导致入侵减少了 2 倍。这可能与膜的疏水性和流动性的变化有关。我们的研究表明，生长培养基的营养组成可以影响益生菌生存能力的技术特性。
