SRA

Listeria monocytogenes is a human, food-borne pathogen. Genomic comparisons between L. monocytogenes and Listeria innocua, a closely related non-pathogenic species, were pivotal in the identification of protein coding genes essential for virulence. However, no comprehensive comparison has focused on the non-coding genome. We used strand-specific cDNA sequencing to produce genome-wide transcription start site (TSS) maps for both organisms, and developed a publicly available integrative browser to visualize and analyze both transcriptomes in different growth conditions and genetic backgrounds. Our data revealed conservation across most transcripts, but significant divergence between the species in a subset of non-coding RNAs. In L. monocytogenes we identified 113 sRNAs and 70 asRNAs, significantly increasing the repertoire of non coding RNAs in this species. Remarkably, we identified a class of long antisense transcripts (lasRNAs) that overlap one gene while also serving as the 5' UTR of the adjacent divergent gene. Experimental evidence suggests that lasRNAs transcription inhibits expression of one operon while activating the expression of another. Such lasRNA/operon structure, termed "excludon", might represent a novel form of regulation in bacteria. Overall design: Construction of consensus TSS-maps in Listeria monocytogenes and Listeria innocua by applying 5'-end sequencing on samples in different conditions and genetic backgrounds.