School of Food Science, Washington State University, Pullman, WA 99163, USA.
Appl Environ Microbiol. 2011 Aug;77(15):5257-69. doi: 10.1128/AEM.02845-10. Epub 2011 Jun 3.
Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were used to study the cell injury and inactivation of Campylobacter jejuni from exposure to antioxidants from garlic. C. jejuni was treated with various concentrations of garlic concentrate and garlic-derived organosulfur compounds in growth media and saline at 4, 22, and 35°C. The antimicrobial activities of the diallyl sulfides increased with the number of sulfur atoms (diallyl sulfide < diallyl disulfide < diallyl trisulfide). FT-IR spectroscopy confirmed that organosulfur compounds are responsible for the substantial antimicrobial activity of garlic, much greater than those of garlic phenolic compounds, as indicated by changes in the spectral features of proteins, lipids, and polysaccharides in the bacterial cell membranes. Confocal Raman microscopy (532-nm-gold-particle substrate) and Raman mapping of a single bacterium confirmed the intracellular uptake of sulfur and phenolic components. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to verify cell damage. Principal-component analysis (PCA), discriminant function analysis (DFA), and soft independent modeling of class analogs (SIMCA) were performed, and results were cross validated to differentiate bacteria based upon the degree of cell injury. Partial least-squares regression (PLSR) was employed to quantify and predict actual numbers of healthy and injured bacterial cells remaining following treatment. PLSR-based loading plots were investigated to further verify the changes in the cell membrane of C. jejuni treated with organosulfur compounds. We demonstrated that bacterial injury and inactivation could be accurately investigated by complementary infrared and Raman spectroscopies using a chemical-based, "whole-organism fingerprint" with the aid of chemometrics and electron microscopy.
傅里叶变换红外（FT-IR）光谱和拉曼光谱用于研究从大蒜抗氧化剂暴露中受到影响的空肠弯曲菌的细胞损伤和失活。将空肠弯曲菌用各种浓度的大蒜浓缩物和大蒜衍生的有机硫化合物在生长培养基和盐水中于 4、22 和 35°C 下进行处理。二烯丙基硫化物的抗菌活性随硫原子数的增加而增加（二烯丙基硫化物<二烯丙基二硫化物<二烯丙基三硫化物）。FT-IR 光谱证实，有机硫化合物是空肠弯曲菌抗菌活性的主要原因，其活性远大于大蒜酚类化合物，这表明细菌细胞膜中蛋白质、脂质和多糖的光谱特征发生了变化。共焦拉曼显微镜（532nm-金颗粒基底）和单个细菌的拉曼图谱证实了硫和酚类成分的细胞内摄取。扫描电子显微镜（SEM）和透射电子显微镜（TEM）用于验证细胞损伤。进行了主成分分析（PCA）、判别函数分析（DFA）和类模拟的软独立建模（SIMCA），并进行了交叉验证，以根据细胞损伤程度区分细菌。采用偏最小二乘回归（PLSR）对处理后剩余的健康和受损细菌细胞的实际数量进行定量和预测。研究了 PLSR 基于的加载图，以进一步验证用有机硫化合物处理的空肠弯曲菌细胞膜的变化。我们证明了可以通过使用基于化学的“全生物体指纹”结合化学计量学和电子显微镜，使用互补的红外和拉曼光谱来准确研究细菌损伤和失活。
