Department of Veterinary Disease Biology, University of Copenhagen, Stigboejlen 4, 1870 Frederiksberg C, Denmark.
Food Microbiol. 2013 Apr;33(2):221-7. doi: 10.1016/j.fm.2012.09.020. Epub 2012 Oct 6.
Salmonellae are often present as immobilized cells in food products in the form of micro-colonies. Despite this, most research into Salmonella physiology has been performed with bacteria grown as planktonic cultures. In the current study, we compared the transcriptome of planktonic and immobilized Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) subjected to 30 min of heat stress at 45 °C. The expression of 538 genes was differently regulated between the two conditions after 30 min. Heat stress of an immobilized culture induced expression of flagella and virulence genes compared to the non-heat stressed immobilized bacteria. Immobilized heat stressed S. Typhimurium was more invasive in HeLa cells than the non-heat stressed controls, whereas the heat stress caused planktonic bacteria to be less invasive. The decrease in invasion of heat stressed planktonic cultures returned to non-heat stressed levels 30 min post treatment, whereas the increased invasion of HeLa cells of the heat stressed immobilized cultures still remained 30 min after the heat stress was terminated. This study shows that immobilized bacteria respond to heat stress differently than planktonic bacteria.
沙门氏菌通常以微菌落的形式作为固定细胞存在于食品中。尽管如此，大多数对沙门氏菌生理学的研究都是在浮游培养物中生长的细菌进行的。在当前的研究中，我们比较了浮游和固定的鼠伤寒沙门氏菌亚种（鼠伤寒沙门氏菌）在 45°C 下经受 30 分钟热应激时的转录组。30 分钟后，两种条件下有 538 个基因的表达存在差异调控。与非热应激固定细菌相比，固定培养物的热应激诱导了鞭毛和毒力基因的表达。与非热应激对照相比，固定热应激的鼠伤寒沙门氏菌在 HeLa 细胞中的侵袭性更强，而热应激导致浮游细菌的侵袭性降低。热应激浮游培养物的侵袭性下降在处理后 30 分钟恢复到非热应激水平，而热应激固定培养物的 HeLa 细胞侵袭性增加仍在热应激终止后 30 分钟保持。这项研究表明，固定细菌对热应激的反应与浮游细菌不同。
