MOST-USDA Joint Research Center for Food Safety and Bor Luh Food Safety Center, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, PR China.
Foodborne Pathog Dis. 2012 Mar;9(3):265-71. doi: 10.1089/fpd.2011.1033.
Thermonuclease is known as a specific virulence factor in Staphylococcus aureus. It is widely used as a genetic marker for detection of S. aureus in various types of food. Previous studies have revealed the existence of two functional thermostable nucleases encoded by two different genes (nuc1 and nuc2) in S. aureus. To identify the expression characteristics of these two genes, comparative mRNA analysis of nuc1 and nuc2 was carried out by quantitative real-time polymerase chain reaction (PCR). Distinct expression patterns were observed at different growth stages, and expression was under the control of the sae regulatory system in strain RN4220. The maximum level of nuc1 transcripts was at the post-exponential growth phase, and expression was notably down-regulated in a sae mutant. In contrast, nuc2 transcript levels declined after the early exponential phase, and they were slightly up-regulated in the sae mutant. Furthermore, unlike the expression of nuc1, which varied in three different S. aureus clinical strains, the transcription of nuc2 remained relatively constant. The nuc1 transcription level correlated well with thermonuclease activity results, which suggests that nuc1 plays a primary role in thermonuclease activity in S. aureus. This information will be useful for understanding thermonuclease gene function and alterations of regulation for pathogenesis and diagnosis of S. aureus.
耐热核酸酶是金黄色葡萄球菌中一种特定的毒力因子。它被广泛用作各种类型食品中金黄色葡萄球菌检测的遗传标记。先前的研究表明，金黄色葡萄球菌中存在两种由不同基因（nuc1 和 nuc2）编码的具有功能的耐热核酸酶。为了鉴定这两个基因的表达特征，通过定量实时聚合酶链反应（PCR）对 nuc1 和 nuc2 进行了比较 mRNA 分析。在不同的生长阶段观察到不同的表达模式，并且在 RN4220 菌株中受 sae 调节系统的控制。nuc1 转录物的最大水平出现在指数生长后期，在 sae 突变体中表达明显下调。相比之下，nuc2 的转录水平在早期指数期后下降，在 sae 突变体中略有上调。此外，与 nuc1 的表达不同，nuc1 在三种不同的金黄色葡萄球菌临床菌株中变化，nuc2 的转录保持相对恒定。nuc1 的转录水平与耐热核酸酶活性结果密切相关，这表明 nuc1 在金黄色葡萄球菌的耐热核酸酶活性中起主要作用。这些信息将有助于理解耐热核酸酶基因的功能以及调控变化对于金黄色葡萄球菌发病机制和诊断的影响。
