Horton A J, Hak K M, Steffan R J, Foster J W, Bej A K
Department of Biology, The University of Alabama at Birmingham, 35294, USA.
Antonie Van Leeuwenhoek. 2000 Jan;77(1):13-20. doi: 10.1023/a:1002055719798.
Salmonella typhimurium is a major foodborne microbial pathogen which primarily contaminates poultry products causing salmonellosis in humans. S. typhimurium LT2 cultures, when transferred from 37 degrees C to 5 degrees C or 10 degrees C, showed an initial lag period in growth with an approximate generation time of 10-25 h. Western blot assay using E. coli CS7.4 antibody and analysis of radiolabeled total cellular proteins from S. typhimurium cultures after exposure to 10 degrees C or 5 degrees C showed elevated expression of a major cold shock protein, CS7.4. Identification of a decreased level of CS7.4 at 37 degrees C suggests that the expression of this protein may require a large temperature downshift. Putative regulatory protein binding segment on the 5'-untranslated region referred as 'Fragment 7' in S. typhimurium exhibited a 90.6% and a 56.25% nucleotide sequence identity when compared with the Fragment 7 of E. coli and S. enteritidis, respectively. The differences in the nucleotide sequence within the Fragment 7 between S. typhimurium and S. enteritidis may explain the differential expression of CspA at 37 degrees C. The nucleotide sequence of the open reading frame of S. typhimurium cspA gene showed a single base difference at 816 bp position from a G to a C which altered the amino acid residue from a glycine to an alanine. In addition to CspA, an elevated expression of a 105 kDa, and decreased expression of 6 proteins were evidenced when cultures of S. typhimurium were exposed to 10 degrees C or 5 degrees C. Differential expression of the CspA and other proteins in S. typhimurium following exposure to cold temperatures suggest that adaptation and continued growth and survival at cold temperatures in this pathogen may be aided by these cold-responsive proteins.
鼠伤寒沙门氏菌是一种主要的食源性病原体，主要污染家禽产品，可导致人类感染沙门氏菌病。鼠伤寒沙门氏菌LT2培养物从37℃转移至5℃或10℃时，生长出现初始延迟期，代时约为10 - 25小时。使用大肠杆菌CS7.4抗体的蛋白质免疫印迹分析以及对暴露于10℃或5℃后的鼠伤寒沙门氏菌培养物的放射性标记总细胞蛋白分析表明，一种主要的冷休克蛋白CS7.4表达升高。在37℃时CS7.4水平降低，这表明该蛋白的表达可能需要大幅度降温。鼠伤寒沙门氏菌5'-非翻译区上被称为“片段7”的推定调节蛋白结合片段，与大肠杆菌和肠炎沙门氏菌的片段7相比，核苷酸序列同一性分别为90.6%和56.25%。鼠伤寒沙门氏菌和肠炎沙门氏菌片段7内核苷酸序列的差异可能解释了CspA在37℃时的差异表达。鼠伤寒沙门氏菌cspA基因开放阅读框的核苷酸序列在816 bp位置有一个单碱基差异，从G变为C，这使得氨基酸残基从甘氨酸变为丙氨酸。除了CspA，当鼠伤寒沙门氏菌培养物暴露于10℃或5℃时，还证实了一种105 kDa蛋白表达升高，6种蛋白表达降低。鼠伤寒沙门氏菌在暴露于低温后CspA和其他蛋白的差异表达表明，这些冷反应蛋白可能有助于该病原体在低温下适应、持续生长和存活。
