Concluding Remarks

Abstract

There are some old paradigms relating to HS which have to be replaced by new ones. There is clearly no process in freshwater systems that is not directly or indirectly influences by these substances. HS act as UV-shields and radical scavengers, and have done so previously. It is strongly hypothesized that without HS or HS-like substances, the formation of biomolecules during the development of life on Earth would not have taken place. Simultaneously the biomolecules would have been oxidized during the very formation process. In contrast, HS interact with biomolecules such as enzymes, hemoglobin, or DNA, such that the biomolecules must escape from or even repel their protectors against UV light and radicals. A harmless juxtaposition of the already existing biomolecules and the HS or HS-like substances was not possible. The biomolecules must immediately open metabolic routes which dispose of HS or HS-like substances. The biotransformation systems must probably have been established as one of the first metabolic pathways, and this could be one reason why the biotransformation system is extremely conservative in all organisms.