Goverde R L, Huis in't Veld J H, Kusters J G, Mooi F R
University of Utrecht, Faculty of Veterinary Medicine, Department of the Science of Food of Animal Origin, The Netherlands.
Mol Microbiol. 1998 May;28(3):555-69. doi: 10.1046/j.1365-2958.1998.00816.x.
The psychrotrophic bacterium Yersinia enterocolitica is characterized by temperature-dependent adaptations. To investigate Y. enterocolitica genes involved in cold adaptation, a mutant restricted in its ability to grow at 5 degrees C was isolated from a transposon mutant library. The transposon insertion site in this psychrotrophy-defective (PD) mutant mapped 16 bp upstream of an open reading frame whose predicted amino acid sequence showed 93% similarity with the Escherichia coli exoribonuclease polynucleotide phosphorylase (PNPase), encoded by pnp. Expression of this gene was blocked in the PD mutant. However, the introduction of a second copy of pnp, including 0.33 kbp sequences upstream of its coding region, into the chromosome of the PD mutant restored pnp expression as well as the ability to grow at 5 degrees C. Furthermore, the expression of pnp appeared to be temperature dependent: in the parental Y. enterocolitica strain, the levels of both pnp mRNA and PNPase were 1.6-fold higher at 5 degrees C compared with 30 degrees C. A similarly enhanced level of PNPase at 5 degrees C was observed in the merodiploid recombinant strain, which indicates that the 0.33 kbp region upstream of pnp harboured a cold-inducible promoter. A putative cold shock promoter motif (ATTGG) was observed in this region.
嗜冷细菌小肠结肠炎耶尔森菌具有温度依赖性适应特征。为了研究参与冷适应的小肠结肠炎耶尔森菌基因，从转座子突变体文库中分离出一株在5℃下生长能力受限的突变体。该嗜冷缺陷（PD）突变体中的转座子插入位点位于一个开放阅读框上游16 bp处，其预测的氨基酸序列与大肠杆菌外切核糖核酸酶多核苷酸磷酸化酶（PNPase，由pnp编码）有93%的相似性。该基因在PD突变体中的表达被阻断。然而，将包括其编码区上游0.33 kbp序列的pnp第二拷贝引入PD突变体的染色体中，恢复了pnp的表达以及在5℃下生长的能力。此外，pnp的表达似乎具有温度依赖性：在亲本小肠结肠炎耶尔森菌菌株中，与30℃相比，5℃时pnp mRNA和PNPase的水平均高出1.6倍。在部分二倍体重组菌株中，5℃时也观察到类似的PNPase水平增强，这表明pnp上游0.33 kbp区域含有一个冷诱导启动子。在该区域观察到一个假定的冷休克启动子基序（ATTGG）。
