Microbial degradation of environmentally harmful guanidines

• Applicant: Professor Dr. Jörg Steffen Hartig
• Subject Area: Biological and Biomimetic Chemistry
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 585724039

The increasing release of bioactive compounds of anthropogenic origin represents a growing environmental and human health concern. Guanidine derivatives are a class of especially persistent compounds that has been largely neglected until now. Synthetic guanidines are chemically stable and thus poorly biodegradable, which results in their accumulation in the environment. Bioremediation with specifically selected and optimised enzymes and microorganisms represents a promising approach that has been successfully investigated for several compound classes, including organophosphates and organohalides. However, such approaches have yet to be applied for the remediation of harmful and persistent guanidines. In the course of our recent research, we have identified and characterised several bacterial enzymes and pathways that degrade potentially harmful guanidines. However, the substrate spectrum of naturally occurring enzymes is mostly limited to biogenic guanidines, whereas industrially produced guanidines are poorly metabolised. While biodegradation has been observed for certain guanidine derivatives, the underlying enzymes and pathways remain unknown. Recently, we characterised the key enzyme for the degradation of metformin and its putative evolutionary precursor. Metformin is an anti-diabetes type II drug and constitutes one of the most prescribed pharmaceuticals worldwide. Metformin and its metabolites have been detected in surface, ground and even drinking water around the world. The objective of this project is to establish a screening platform for isolating microbes that degrade harmful guanidines. In the past, we have already identified and characterized microbial activities and pathways that degrade free guanidine as well as the diabetes drug metformin. In preliminary work, we have now isolated a bacterium that degrades diphenylguanidine, a harmful vulcanization additive that is released and accumulates in the environment. By identifying and characterising enzymes capable of degrading this additive, we will improve our understanding of how these substances behave and persist in the environment, and lay the groundwork for developing bioremediation strategies for persistent guanidines. To this end, we will combine our expertise in catabolic pathway and enzyme discovery and in structural and functional characterisation to identify robust catalysts for bioremediation. The project will provide novel strategies for remediating the environment of harmful guanidines of both biotic and anthropogenic origin, thus making a significant contribution to environmental sustainability.

• DFG Programme: Research Grants