K-mer frequency distribution curve. All 17-mer sequences were extracted from pre-processed high-quality paired-end reads and plotted the frequency (y-axis) as a function of the depth (x-axis). (A) k-mer curve for L. pallidum. The single main peak indicates a homozygous genomic source. (B) k-mer curve for L. scutellare. Instead of a single peak, minor residual peaks are also shown, indicating the heterozygous nature of the isolated genomic material.