Modugno Chloé, Peltier Caroline, Simonin Hélène, Dujourdy Laurence, Capitani Francesco, Sandt Christophe, Perrier-Cornet Jean-Marie
AgroSup Dijon, PAM UMR A 02.102, Université Bourgogne Franche-Comté, Dijon, France.
AgroSup Dijon, Service d'Appui à la Recherche, Dijon, France.
Front Microbiol. 2020 Jan 31;10:3122. doi: 10.3389/fmicb.2019.03122. eCollection 2019.
Bacterial spores are extremely resistant life-forms that play an important role in food spoilage and foodborne disease. The return of spores to a vegetative cell state is a three-step process, these being activation, germination, and emergence. High-pressure (HP) processing is known to induce germination in part of the spore population and even to inactivate a high number of spores when combined with other mild treatments such as the addition of nisin. The aim of the present work was to investigate the mechanisms involved in the sensitization of spores to nisin following HP treatment at ambient temperature or with moderate heating leading to a heterogeneous spore response. spores were subjected to HP treatment at 500 MPa at 20 and 50°C. The physiological state of different subpopulations was characterized. Then Fourier transform infrared (FTIR) microspectroscopy coupled to a synchrotron infrared source was used to explore the heterogeneity of the biochemical signatures of the spores after the same HP treatments. Our results confirm that HP at 50°C induces the germination of a large proportion of the spore population. HP treatment at 20°C generated a subpopulation of ungerminated spores reversibly sensitized to the presence of nisin in their growth medium. Regarding infrared spectra of individual spores, spores treated by HP at 50°C and germinated spores had similar spectral signatures involving the same structural properties. However, after HP was performed at 20°C, two groups of spores were distinguished; one of these groups was clearly identified as germinated spores. The second group displayed a unique spectral signature, with shifts in the spectral bands corresponding to changes in membrane fluidity. Besides, spores spectra in the amide region could be divided into several groups close to spectral properties of dormant, germinated, or inactivated spores. The part of the spectra corresponding to α-helix and β-sheet-structures contribute mainly to the spectral variation between spores treated by HP at 20°C and other populations. These changes in the lipid and amide regions could be the signature of reversible changes linked to spore activation.
细菌芽孢是极具抗性的生命形式，在食品变质和食源性疾病中起着重要作用。芽孢恢复到营养细胞状态是一个三步过程，即激活、萌发和出芽。已知高压（HP）处理可诱导部分芽孢群体萌发，甚至在与其他温和处理（如添加乳链菌肽）联合使用时能使大量芽孢失活。本研究的目的是探究在常温或适度加热的HP处理后芽孢对乳链菌肽敏感化所涉及的机制，这种处理会导致芽孢产生异质性反应。将芽孢在20℃和50℃下于500MPa进行HP处理。对不同亚群体的生理状态进行了表征。然后，使用与同步加速器红外光源耦合的傅里叶变换红外（FTIR）显微光谱法来探究相同HP处理后芽孢生化特征的异质性。我们的结果证实，50℃的HP处理可诱导大部分芽孢群体萌发。20℃的HP处理产生了一个未萌发芽孢的亚群体，该亚群体对其生长培养基中乳链菌肽的存在产生可逆性敏感。关于单个芽孢的红外光谱，50℃HP处理的芽孢和已萌发芽孢具有相似的光谱特征，涉及相同的结构特性。然而，在20℃进行HP处理后，区分出了两组芽孢；其中一组被明确鉴定为已萌发芽孢。第二组呈现出独特的光谱特征，光谱带的移动对应于膜流动性的变化。此外，酰胺区域的芽孢光谱可分为几组，接近休眠、已萌发或失活芽孢的光谱特性。对应于α-螺旋和β-折叠结构的光谱部分主要导致了20℃HP处理的芽孢与其他群体之间的光谱变化。脂质和酰胺区域的这些变化可能是与芽孢激活相关的可逆变化的特征。
