Pure and modified humic substances exert mild stress and affect Caenorhabditis elegans life span

When studying and reviewing the ecological role of humic substances in freshwaters (leachates from the soils in the catchments, which make natural freshwaters light to dark brown and which comprise approximately 10-times more organic carbon than all living beings in the same water volume) we tested the nematode Caenorhabditis elegans.

Although maintained in the laboratory for countless generations, this worm has an inherent affinity toward a humic material containing environment. This material switches on olfactory genes and, hence, he actively migrates into humic-rich environments. This simple experiment made our team curious and it conducted many more experiments on the interaction of dissolved humic material with freshwater organisms.

So it could shown that humic substances enriched with hydroxybenzene moieties caused a significantly increased tolerance to thermal stress in C. elegans and extended its lifespan. Exposed nematodes showed delayed linear growth and onset of reproduction and a stronger pumping activity of the pharynx. Thus, treated nematodes act younger than they really are. In this feature the modified humic substances replicated the biological impact of hydroquinone-homopolymers and various plant polyphenol monomers, thereby supporting the hydroxybenzene moieties of humic substances as major effective structures for the physiological effects observed in C. elegans.