Biotechnology, Microbiology and Food Safety, Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
Yeast. 2010 Apr;27(4):217-28. doi: 10.1002/yea.1746.
In this contribution, the influence of various physicochemical factors on Saccharomyces cerevisiae invasive growth is examined quantitatively. Agar-invasion assays are generally applied for in vitro studies on S. cerevisiae invasiveness, the phenomenon observed as a putative virulence trait in this clinically more and more concerning yeast. However, qualitative agar-invasion assays, used until now, strongly limit the feasibility and interpretation of analyses and therefore needed to be improved. Besides, knowledge in this field concerning the physiology of invasive growth, influenced by stress conditions related to the human alimentary tract and food, is poor and should be expanded. For this purpose, a quantitative agar-invasion assay, presented in our previous work, was applied in this contribution to clarify the significance of the stress factors controlling the adhesion and invasion of the yeast in greater detail. Ten virulent and non-virulent S. cerevisiae strains were assayed at various temperatures, pH values, nutrient starvation, modified atmosphere, and different concentrations of NaCl, CaCl2 and preservatives. With the use of specific parameters, like a relative invasion, eight invasive growth models were hypothesized, which enabled intelligible interpretation of the results. A strong preference for invasive growth (meaning high relative invasion) was observed when the strains were grown on nitrogen- and glucose-depleted media. A significant increase in the invasion of the strains was also determined at temperatures typical for human fever (37-39 degrees C). On the other hand, a strong repressive effect on invasion was found in the presence of salts, anoxia and some preservatives.
在本研究中，定量研究了各种物理化学因素对酿酒酵母侵袭性生长的影响。琼脂侵袭实验通常用于体外研究酿酒酵母的侵袭性，这种现象被认为是该临床相关酵母的一种潜在毒力特征。然而，迄今为止使用的定性琼脂侵袭实验极大地限制了分析的可行性和解释，因此需要改进。此外，关于受人类消化道和食物相关应激条件影响的侵袭性生长生理学的相关知识还很匮乏，需要进一步拓展。为此，本研究应用了我们之前提出的一种定量琼脂侵袭实验，以更详细地阐明控制酵母黏附和侵袭的应激因素的重要性。在不同温度、pH 值、营养饥饿、改良气氛以及不同浓度的 NaCl、CaCl2 和防腐剂条件下，对 10 株毒力和非毒力酿酒酵母菌株进行了检测。使用特定参数，如相对侵袭性，提出了 8 种侵袭性生长模型，从而可以对结果进行合理的解释。当菌株在氮和葡萄糖耗尽的培养基中生长时，侵袭性生长（高相对侵袭性）的偏好性较强。在人类发热的典型温度（37-39 摄氏度）下，菌株的侵袭性也显著增加。另一方面，盐、缺氧和某些防腐剂的存在对侵袭性有很强的抑制作用。
