Table 1

Horizontally transferred genes inChlamydia trachomatis.

Chlamydial geneSupport for horizontal transfer
Topoisomerase I, COOH-terminal domain (CT643), and stand-alone SWIB protein (CT460)The α-helical SWIB domain detected only in eukaryotic chromatin-associated proteins.
SET domain protein (CT737)SET domain found only in numerous eukaryotic chromatin-associated proteins.
Methionyl-tRNA synthetase (Met-RS) (CT032)Chlamydial Met-RS groups with eukaryotic ones in phylogenetic analysis. A C2C2 “little finger” domain is conserved in Chlamydia, Archaea, and eukaryotes, to the exclusion of the other bacteria. An accessory, COOH-terminal RNA-binding domain is present in bacterial Met-RS, but not inChlamydia, Archaea, or eukaryotes.
Pyrophosphate-dependent phosphofructokinase 1 and 2 (CT205, CT207)Much greater similarity to eukaryotic than to bacterial orthologs, with the exception of the spirochetes.
Glucose-1-phosphate adenylyltransferase (CT489)Supported by phylogenetic analysis (39); likely chloroplast origin in plants.
Glycogen phosphorylase (CT248)Supported by phylogenetic analysis (39).
UDP-glucose pyrophosphorylase (CT715)No easily detectable bacterial homologs.
Adenine nucleotide translocases 1 and 2 (CT495, CT065)ATP/ADP translocases of this family are detectable only in Rickettsia and in plants.
Glycerol-3-phosphate acyltransferase (CT807)So far detected only in plants.
β-ketoacyl-ACP synthase (CT770)Supported by phylogenetic analysis (39).
Enoyl-ACP reductase (CT104)Much greater similarity to eukaryotic than to bacterial orthologs; see phylogenetic analysis (Fig. 3).
Biotin-protein ligase (CT035)So far detectable only in two yeast species.
V-type ATPase operon (CT304-310)Grouping with spirochetes to the exclusion of Archaea is apparent.
Adenovirus type thiol protease (CT867, CT868)Poorly conserved but common in eukaryotes; among prokaryotes, detected only in E. coli.
Thioredoxin peroxidase (CT603)Supported by phylogenetic analysis (39).
Superoxide dismutase (CT294)Supported by phylogenetic analysis (39).
Putative metal-dependent hydrolase (CT386)So far detected only in yeast and C. elegans.
Uncharacterized, conserved protein (CT472)So far detected only in yeast and C. elegans.
Tryptophan operon (CT169-171)Tryptophan repressor has been found only in Proteobacteria, suggesting that the whole operon has been acquired by horizontal transfer.
Predicted ATPase (CT402)So far found only in Proteobacteria.