A putative operon. Gene expression measurements from a genomic region of Salmonella typhimurium. The genome is represented as two barplots, one for each strand. Each gene has three bars representing expression at 4 h, 8 h and 12 h post macrophage infection. Gene expression measurements (y-axis) are ratios of test RNA to control RNA on the log 2 scale. Distance between genes is relative and representative of intergenic distance. The image shows six genes that have been identified by ProGenExpress as potentially interesting. The genes are very close together on the genome and display similar expression patterns, and therefore could represent an as yet unannotated operon. The genes have synonyms STM4257 – STM4262 and currently have no confirmed function.