On the origin of genomic adaptation at high temperature for prokaryotic organisms.
For a long time, the central issue of evolutionary genomics was to find out the adaptive strategy of nucleic acid molecules of various microorganisms having different optimal growth temperatures (Topt). Long-standing controversies exist regarding the correlations between genomic G+C content and Topt, and this debate has not been yet settled. We address this problem by considering the fact that adaptation to growth at high temperature requires a coordinated set of evolutionary changes affecting: (i) nucleic acid thermostability and (ii) stability of codon-anticodon interactions. In the present study, we analyzed 16 prokaryotic genomes having intermediate G+C content and widely varying optimal growth temperatures. Results show that elevated growth temperature imposes selective constraints not only on nucleic acid level but also affects the stability of codon-anticodon interaction. We observed a decrease in the frequency of SSC and SSG codons with the increase in Topt to avoid the formation of side-by-side GC base pairs in the codon-anticodon interaction, thereby making it impossible for a genome to increase GC composition uniformly through the whole coding sequence. Thus, we suggest that any attempt to obtain a generalized relation between genomic GC composition and optimal growth temperature would hardly evolve any satisfactory result.
Basak
Surajit
S
Bioinformatics Centre, Bose Institute, P 1/12, C.I.T. Scheme VII M, Kolkata 700 054, India.
Ghosh
Tapash Chandra
TC
D000222:Adaptation, Physiological / Q000235:genetics*; D001482:Base Composition; D020029:Base Pairing; D019143:Evolution, Molecular; D016678:Genome; D006358:Hot Temperature; D011387:Prokaryotic Cells / Q000737:chemistry / Q000378:metabolism*