Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland.
Food Microbiol. 2010 Aug;27(5):653-60. doi: 10.1016/j.fm.2010.02.009. Epub 2010 Mar 9.
The cold growth phenotypes and transcriptional activation of cold stress adaptation genes was evaluated amongst Listeria monocytogenes strains from human listeriosis cases, food products and associated production environments. Significant cold growth phenotypic variation was observed during growth of such strains in rich (BHI) as well as chemically defined minimal (MDM) nutrient conditions. While all twenty analyzed strains grew in BHI at 4 degrees C, only eight of these strains, mostly those recovered from human listeriosis cases, were also able to grow in MDM under similar cold stress. The cold growth phenotypes observed in BHI were used to define two categories of five strains each, which either displayed enhanced and poor cold tolerance relative to the rest of the strain collection. The first group (GP1) consisted of strains characterized by short lag times, whilst the second group (GP2) comprised of strains displaying prolonged lag times before growth resumption during incubation in BHI cultures at 4 degrees C. Transcription level activation of sigB, cspA and pgpH gene expression associated with cold stress exposure in a selection of GP1 and GP2 strains was assessed. Despite similar cold dependent sigB transcript induction between these two strain groups, there were significant differences observed in cold stress dependent induction of cspA and pgpH transcripts. Cold tolerant GP1 strains displayed relatively higher transcriptional activation of cspA and pgpH after cold stress exposure compared to the cold sensitive GP2 strains. This study highlights strain variability in cold stress tolerance phenotypes, as well as in strain capacity to activate specific cold adaptation gene expression responses. In addition the study also shows that enhanced and poor cold growth phenotypes are associated with particular strain capacity to activate important cold stress gene expression responses upon transition of L. monocytogenes into low temperature environments.
在人类李斯特菌病病例、食品产品和相关生产环境中分离的李斯特菌菌株中，评估了冷生长表型和冷应激适应基因的转录激活。在丰富（BHI）和化学定义的最小（MDM）营养条件下，这些菌株的生长过程中观察到明显的冷生长表型变异。虽然所有 20 株分析的菌株在 4°C 的 BHI 中都能生长，但只有其中的 8 株，主要是从人类李斯特菌病病例中分离出来的，也能在类似的冷应激条件下在 MDM 中生长。在 BHI 中观察到的冷生长表型用于定义两个五株菌株组，每个组都显示出相对于菌株集合的其他菌株增强和较差的耐寒性。第一组（GP1）由具有短迟滞时间的菌株组成，而第二组（GP2）由在 4°C 的 BHI 培养物中孵育时恢复生长之前表现出延长迟滞时间的菌株组成。评估了一组 GP1 和 GP2 菌株中与冷应激暴露相关的 sigB、cspA 和 pgpH 基因表达的转录水平激活。尽管这两个菌株组之间存在相似的冷依赖性 sigB 转录诱导，但在 cspA 和 pgpH 转录的冷应激依赖性诱导方面观察到显著差异。冷耐受 GP1 菌株在冷应激暴露后显示出相对较高的 cspA 和 pgpH 转录激活，而冷敏感 GP2 菌株则较低。本研究强调了冷应激耐受表型以及菌株激活特定冷适应基因表达反应的能力的菌株变异性。此外，该研究还表明，增强和较差的冷生长表型与李斯特菌进入低温环境时特定菌株激活重要冷应激基因表达反应的能力有关。
