Hydrolysis reactions
DNA decay by hydrolysis can occur abiotically and be enzymatically mediated and is affected by environmental factors (e.g., water pH, temperature, and ionic strength). DNA strands break through enzymatic hydrolysis by so-called DNases. Such DNA enzymatic hydrolysis can occur at high rates and become the main driver of DNA decay as opposed to purely abiotic hydrolysis3,15. Determining how environmental parameters change enzymatic hydrolysis rates is complicated by the fact that each species’ enzymes potentially exhibit optimal kinetics for different possible combinations of environmental parameters because of a species’ evolutionary history of adaptation43.
Abiotic hydrolysis reactions, such as depurination (loss of purine base) and deamination of cytosine (elimination of ammonia), followed by strand break cause DNA decay. Chemical depurination rates decrease with decreasing temperature, pH, and ionic strength. Deamination reactions are very slow at temperatures present for most of earth’s surface waters (excluding hydrothermal vents) and are therefore unlikely to be an important driver of DNA decay on short time scales of days to weeks44. In fact, most estimates of abiotically driven hydrolysis (depurination and deamination) of DNA have half-lives between 70 and 31,000,000 years, but these can be modulated by extreme environmental conditions3.