%GC of singleton genes was also included in the histogram. Table 3 Serovar to serovar difference expressed in percent   1 3 6 14 2 4 5 7 8 9 10 11 12 13 1   0.66 0.52 0.75 9.90 9.99 9.68 9.78 9.66 10.23 9.84 9.70 9.93 9.79 3 0.70   0.49 0.35 9.93 9.67 9.33 9.43 9.33 10.01 9.43 CHIR98014 manufacturer 9.36 9.66 9.84 6 0.62 0.52   0.50 9.82 9.82 9.40 9.49 9.38 9.95

9.53 9.42 9.76 9.75 14 0.83 0.33 0.45   9.92 10.01 9.59 9.69 9.57 9.99 9.70 9.60 9.95 9.83 2 9.82 9.87 9.58 9.81   0.86 0.74 0.78 0.76 1.25 0.74 0.77 0.86 0.84 4 9.90 9.60 9.57 9.83 0.94   0.69 0.64 0.69 0.82 0.88 0.66 0.07 0.80 5 9.72 9.31 9.25 SCH727965 mouse 9.52 0.72 0.60   0.15

0.13 0.66 0.56 0.16 0.58 0.66 7 9.72 9.32 9.25 9.52 0.82 0.60 0.16   0.15 0.66 0.53 0.11 0.60 0.67 8 9.76 9.35 9.27 9.54 0.71 0.59 0.08 0.10   0.61 0.51 0.11 0.59 0.65 9 10.90 9.83 9.60 9.71 1.21 0.72 0.63 0.62 0.60   0.85 0.63 0.75 1.08 10 9.79 9.35 9.29 9.56 0.70 0.81 0.51 0.48 0.51 0.87   0.46 0.80 0.43 11 9.73 9.33 9.25 9.52 0.80 0.61 0.16 0.11 0.16 0.67 0.51   0.60 0.64 12 9.85 9.58 9.52 9.79 0.93 0.06 0.67 0.64 0.69 0.85 0.87 0.65   0.80 13 9.70 9.74 9.47 9.66 0.97 PLEKHB2 0.86 0.79

0.76 0.75 1.27 0.56 0.74 0.86   The percent difference was obtained by whole genome comparison on the nucleotide level. Fifty percent of these extra genes encode hypothetical proteins, the rest are spread among different functional categories (Figure  1). Table  4 shows the predicted genes present only in UUR serovars or only in UPA serovars. As it is seen in Figure  1, UUR had more genes encoding cell surface proteins, DNA restriction modification enzyme genes (see S63845 Additional file 3: Comparative paper COGs tables.xls) and remnants of transposons (truncated genes or genes with unverified frameshifts). Furthermore, there are subtle differences in the predicted activities of proteins encoded by various reductase genes among serovars, which may facilitate unequal resistance of different ureaplasmas to oxidative stress during colonization and infection.