From: On the molecular mechanism of GC content variation among eubacterial genomes
Hypotheses | Time | Content | Reference |
---|---|---|---|
UV resistance | 1970 | Since ultraviolet radiation induces the formation of thyminedimers, higher GC content gives a selective advantage to organisms living in niches that are susceptible to direct and intense sunlight. | 16,17 |
Thermal adaptation | 1984 | Thermophilic organisms demonstrate a tendency to high GC content because thermostable and thermolabile amino acids are encoded by GC-rich and GC-poor codons respectively. | 18, 19 |
AT to GC mutation | 1988 | Practically all organisms are subjected to directional mutation pressure and this offers plausible explanations for the intensive GC content heterogeneity among different chromosomal regions of vertebrate genomes. | 20 |
Metabolic resource | 1995 | Differences in directional nucleotide substitution among lineages of mammals can be explained by changes in metabolic physiology. This relationship is thought to be mediated by the effect of oxygen radicals. | 21 |
Coding sequence length | 1996 | The longest coding sequences (exons) of vertebrates and genes of prokaryotes are more GC-rich than the shortest ones. | 22, 23 |
Nitrogen-fixation | 1998 | There is a significantly higher GC content in the nitrogen-fixing members of the genus than in those unable to fix nitrogen. | 24 |
Oxygen requirement | 2002 | Aerobic prokaryotes display a significant increment in genome GC% in relation to anaerobic ones. | 25 |
Environment pressure | 2005 | The GC content of complex microbial communities seems to be globally and actively influenced by the environment, such as bacteria in surface water samples having a GC-content median of around 34%, while for soil samples, it is around 61%. | 26 |
Genome size | 2006 | The relationship between genome size and GC level is valid for aerobic, facultative, and microaerophilic species. | 27 |
DNA polymerase III | 2007 | According to the dimeric combination of alpha subunits, GC contents of eubacterial genomes are partitioned into three groups with distinct GC content variation spectra: dnaE1 (full-spectrum), dnaE2/dnaE1 (high-GC), and polC/dnaE3 (low-GC). | 28 |