Comparative genomics of Thermus thermophilus and Deinococcus radiodurans: divergent routes of adaptation to thermophily and radiation resistance

Open Access
Publisher Website
Google Scholar
Abstract
Background: Thermus thermophilusandDeinococcus radioduransbelong to a distinct bacterial clade but have remarkably different phenotypes.T. thermophilusis a thermophile, which is relatively sensitive to ionizing radiation and desiccation, whereasD. radioduransis a mesophile, which is highly radiation- and desiccation-resistant. Here we present an in-depth comparison of the genomes of these two related but differently adapted bacteria.Results: By reconstructing the evolution ofThermusandDeinococcusafter the divergence from their common ancestor, we demonstrate a high level of post-divergence gene flux in both lineages. Various aspects of the adaptation to high temperature inThermuscan be attributed to horizontal gene transfer from archaea and thermophilic bacteria; many of the horizontally transferred genes are located on the single megaplasmid ofThermus. In addition, theThermuslineage has lost a set of genes that are still present inDeinococcusand many other mesophilic bacteria but are not common among thermophiles. By contrast,Deinococcusseems to have acquired numerous genes related to stress response systems from various bacteria. A comparison of the distribution of orthologous genes among the four partitions of theDeinococcusgenome and the two partitions of theThermusgenome reveals homology between theThermusmegaplasmid (pTT27) andDeinococcusmegaplasmid (DR177).Conclusion: After the radiation from their common ancestor, theThermusandDeinococcuslineages have taken divergent paths toward their distinct lifestyles. In addition to extensive gene loss,Thermusseems to have acquired numerous genes from thermophiles, which likely was the decisive contribution to its thermophilic adaptation. By contrast,Deinococcuslost few genes but seems to have acquired many bacterial genes that apparently enhanced its ability to survive different kinds of environmental stresses. Notwithstanding the accumulation of horizontally transferred genes, we also show that the single megaplasmid ofThermusand the DR177 megaplasmid ofDeinococcusare homologous and probably were inherited from the common ancestor of these bacteria.