Conserved gene strings in prokaryotic genomes: coverage versus depth. Information-density-based alignments (E < 0.1) were used to calculate coverage and alignment depth. The coverage is expressed as the fraction of genes in a genome that are included in conserved gene strings. The depth is expressed as the average number of genes in a column of the template-anchored alignment for the respective genome (A) or the average number of genes in a column that belongs to a conserved gene string (i.e., contains at least one gene) (B). Abbreviations: Bb, Borrelia burgdorferi, Mg,Mycoplasma genitalium; Ssp, Synechocystis sp., Tm,Thermotoga maritima, Uu, Ureaplasma urealyticum.