Harnessing Cosmic Carbon: Anaerobic Microbial Responses to Fullerenes Under Early Earth Conditions

Fullerenes of extra-terrestrial origin may have been accessible as a carbon source for anaerobic microorganisms on the early Earth. Very little is known about how microorganisms respond to and utilise fullerenes and their soluble derivatives, particularly in anoxic environments. We present an investigation into the effects of fullerenes C60 and C70 and their hydroxylated fullerol derivatives on an environmentally relevant anaerobic community and a microbial isolate. Anaerobic microorganisms were cultured in microcosms with suspensions of fullerenes with and without supplementary carbon under different levels of light exposure. Relevant early Earth environmental conditions were simulated by irradiating fullerene suspensions with 254nm UV light for two weeks in the absence of oxygen and the accessibility of the photodegradation products was assessed. We find that the anaerobic community is capable of utilising C60 as a sole carbon source, but that C70 is inhibitory. Additionally, we find that both C60 and C70 fullerol are inhibitory to the anaerobes in this study, which is contradictory to previous studies conducted under aerobic conditions. The anaerobic isolate was unable to grow on C60 alone, but after UV exposure, the C60 photodegradation products served as a highly accessible carbon source. Thus, we present a report on the utilisation of photodegraded C60 as the sole carbon source by an anaerobic microorganism under anoxic conditions. Further data shows that fullerenes and their derivatives can both enhance and inhibit the growth of anaerobic microorganisms, which has important implications for their interactions with early life on Earth and their impact on anoxic environments as pollutants in the present day.