To build on these results, we used a combination of comparative genomics, RNA-seq, and experimental validation by Northern blotting to identify additional sRNAs conserved among the Mycobacteria (Methods). Our computational results provide evidence for 50 conserved small RNAs in Mtb that have not been previously reported. It is likely that additional conserved regions are expressed under other diverse conditions. Figure 5a shows the expression and conservation map for one of our predicted RNAs in the GenomeView Browser [64] . Table 6 shows a listing of the top 12 candidate RNAs. To verify a subset of these candidate small RNAs, we used Northern blot analysis on four of the top predicted regions (Methods). The results (Figure 5b) show signals corresponding to small RNAs from each of four candidates (Table 6 , labeled 1, 2, 3, and 9). All transcripts were near the expected size, or slightly larger. Full-length gels are provided in Additional file 3: Figure S2 . Consistent with previous work, the majority of small RNAs were seen as more than one size transcript [62] . This suggests that small RNAs might be generated by processing of larger transcripts. In the RNAseq data, there are longer "tails" extending outside of the main peak that corresponds to the RNA prediction-different length RNAs could be responsible for the additional bands of higher mass.