Influence of Autoinducer-2 (AI-2) in Cell-Free Supernatant of Salmonella Typhimurium in Gene Expression of S. 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 in the Cell-Free supernatant of S. Typhimurium using mRNA samples from isogenic luxS gene mutant of S. Typhimurium strain 87-26254 grown in LB media in the presence of S. Typhimurium wild type CFS / absence AI-2 (mutant CFS of S. Typhimurium). In the presence of AI-2 in CFS, 758 genes were significantly regulated. Interstingly, AI-2 in CFS caused the down-regulation of 39 genes in Salmonella Pathogenicity Island-1 (SPI-1). Purified cDNAs from the mutant supplemented with CFS containing AI-2 and mutant without AI-2 (Mutant CFS) 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 5 microarray arrays, each with duplicate spots for each gene.