FIG 5 .

Number of predicted sRNAs versus genome size. The number of predicted sRNAs for each clostridial species is plotted against the size of its genome. The number of predicted sRNAs in pathogenic clostridial strains varies linearly with genome size (R² = 0.8901). For species with similar genome sizes (shown within the dashed-line box), the number of predicted sRNAs varies systematically with the type (grouped based on physiological niche) of clostridial species: very low in cellulolytic species, high for pathogenic species, and intermediate for solventogenic and C. kluyveri (this is statistically significant; the t test comparing any two of the three clostridial types gives P values of <0.005).