Influence of Autoinducer-2 (AI-2) in Salmonella Typhimurium Gene Expression. Salmonella enterica subsp. enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium is known to synthesize and respond to the cell signaling molecule, autoinducer-2 (AI-2). The luxS gene is involved in the synthesis of AI-2. We have previously shown that luxS controls a variety of bacterial processes in S. Typhimurium. In this study we identified the genes regulated by AI-2 using mRNA samples from isogenic luxS gene mutant of S. Typhimurium strain 87-26254 grown in LB media in the presence/absence of in vitro synthesized AI-2. In the presence of in vitro synthesized AI-2, 536 genes were significantly (p<0.05) regulated. Interestingly, in vitro synthesized AI-2 caused the down-regulation of 39 genes in Salmonella Pathogenicity Island-1 (SPI-1) including the transcriptional regulators hilA, hilD, and invF. Overall design: Purified cDNAs from the mutant supplemented with AI-2 and mutant without AI-2 (PBS) were each labeled with Cy-3 mono-Reactive Dye and Cy-5 mono-Reactive Dye (GE Health Care, Piscataway, NJ) and were processed using a dye-swapping design. A total of eight microarray arrays, each with duplicate spots for each gene and used for mutant supplemented with AI-2.

鼠伤寒沙门氏菌（Salmonella enterica serovar Typhimurium）已知可合成并响应细胞信号分子自体诱导物-2（autoinducer-2, AI-2）。luxS基因参与AI-2的生物合成。本团队此前已证实，在鼠伤寒沙门氏菌中，luxS可调控多种细菌生理过程。
本研究以在LB培养基中培养的、经体外合成AI-2处理/未处理的鼠伤寒沙门氏菌同基因luxS突变株87-26254的信使RNA（messenger RNA, mRNA）样本，鉴定了受AI-2调控的基因。当添加体外合成的AI-2时，共有536个基因发生显著调控（p<0.05）。值得注意的是，体外合成的AI-2可使沙门氏菌致病岛-1（Salmonella Pathogenicity Island-1, SPI-1）内的39个基因表达下调，其中包括转录调控因子hilA、hilD及invF。
整体实验设计：将添加AI-2的突变株与未添加AI-2（以磷酸盐缓冲液PBS处理）的突变株的互补DNA（complementary DNA, cDNA）分别用Cy-3单反应染料（Cy-3 mono-Reactive Dye）与Cy-5单反应染料（Cy-5 mono-Reactive Dye，通用电气医疗集团，新泽西州皮斯卡塔韦市）标记，并采用染料互换设计开展实验。本研究共使用8张微阵列芯片，每张芯片针对每个基因设有重复斑点，全部用于AI-2处理的突变株样本实验。