Additional file 8.

Chlamydia has lost several steps in the pyrimidine biosynthesis pathway. All chlamydial genomes sequenced thus far, have lost the initial steps involved in pyrimidine biosynthesis. C. pneumoniae (Cpn), C. abortus (Cab), C. caviae (Cav) and C. felis (Cfe) contain a pyrE gene encoding an orotate phosphoribosyltransferase, while C. muridarum (Cmu) and C. trachomatis (Ctr) lack this gene. The next step in the pathway is via pyrF, which is absent from all chlamydial genomes. Interestingly, all six genomes have maintained the last three steps for the conversion of UMP into CTP. Adapted from Koonin and Galperin [66]. Gene names: carA, carbamoyl-phosphate synthase, small subunit; carB, carbamoyl-phosphate synthase, large subunit; pyrB, aspartate carbamoyltransferase; pyrC, dihydroorotase; pyrD, dihydroorotate dehydrogenase; pyrE, orotate phosphoribosyltransferase; pyrF, orotidine 5-phosphate decarboxylase; pyrH, uridylate kinase; ndk, nucleoside diphosphate kinase; pyrG, CTP synthase. Red boxes indicate gene loss, yellow boxes indicate the presence of a gene.

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Mitchell et al. BMC Genomics 2010 11:442   doi:10.1186/1471-2164-11-442