Influence of Autoinducer-2 (AI-2) in Salmonella Typhimurium Gene Expression

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. 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.