Chemosynthesis is a process similar to photosynthesis whereby chemical energy is used by organisms to produce organic compounds, rather than light energy. While photosynthesis predominantly occurs in plants, chemosynthesis is used by many bacteria and archaea species that inhabit extreme environments where light energy is unavailable, such as the deep sea hydrothermal vents. These chemosynthetic microorganisms are able to utilize the chemical energy found in molecules such as hydrogen sulfide, methane, or ammonia to convert carbon dioxide into organic carbon compounds like sugars.
Due to their ability to survive and produce biomass in harsh, aphotic conditions, chemosynthetic microbes have several potential applications in biotechnology. Perhaps the most intriguing is utilizing their metabolic pathways to develop synthetic biology platforms for the production of high-value chemicals and biofuels. Through genetic engineering techniques, the genes and enzymes involved in chemosynthetic carbon fixation could be transferred to more easily manipulable heterotrophic microorganisms. This would endow the host organisms with the capacity for CO2 fixation without the need for light, allowing industrial fermentations to occur continuously instead of in daily batches limited by photosynthesis.
One pathway that has gained significant interest is the Wood-Ljungdahl or acetyl-CoA pathway used by acetogenic bacteria to fix carbon via the Wood-Ljungdahl process. Components of this reductive acetyl-CoA pathway have been successfully introduced into various strains of Escherichia coli and Saccharomyces cerevisiae, demonstrating their ability to fix carbon from CO2 or carbon monoxide with the aid of molecular hydrogen or formate as an electron donor. With additional metabolic engineering, these hosts could potentially be developed into highly effective microbial cell factories for the biosynthesis of fuels, chemicals, and other products directly from waste carbon emissions. This could open up new possibilities for carbon capture and utilization to mitigate climate change.
Beyond synthetic biology applications, natural chemosynthetic communities themselves offer insights into developing sustainable biomanufacturing processes. The symbiotic microbial consortia that have formed around deep-sea hydrothermal vents perform complex metabolisms and biogeochemical cycles that human technologies have yet to replicate. By further characterizing these communities at the molecular level, we may gain understanding into efficient cooperative metabolic designs, electron transfer mechanisms, and self-sufficient closed-loop metabolisms. Lessons learned could then be applied to constructing bioprocessing systems that function harmoniously with their environments. For example, developers of closed photobioreactor systems may take cues from vent symbioses to design Circular- rather than linear-flow biomanufacturing facilities with inherent wastewater treatment.
On the bioremediation front, chemosynthetic microbes demonstrate enormous potential foradb toxic environmental contaminant remediation projects. Several species native to extremepolluted niches have evolved metabolisms that allow them to thrive using toxic substances like heavy metals, radioactive waste, crude oil, or industrial effluent as electron donors or terminal electron acceptors. Through cultivation techniques and metabolic characterization, candidate strains are being identified with promising applications in bioremediating industrial waste, acid mine drainage, and radioactive seepages. Genetic studies of these strains also offer clues into naturally-evolved bioremediation mechanisms that could inspire new biotechnological solutions.
Taking inspiration from natural chemosynthetic microbiomes, synthetic microbial communities may also be engineered for distributed in situ bioremediation applications. By assembling defined consortia of cross-feeding microbes and programming their secretions, researchers could develop ‘designer bioremediation devices’ tailored for distinct contaminated niches and waste streams. Promising early efforts involve programming chemosynthetic acetogens and sulfate-reducing bacteria into syntrophic relationships to remove heavy metals, remediate acid mine drainage, and even produce bioenergy coproducts from wastes. As our insight grows into multi-species interactions within complex microbial communities, the bioengineering of self-sustaining, metal-eating ‘biorobots’ may become feasible propositions for accelerating large-scale bioremediation projects.
In closing, with further research chemosynthesis has notable promise to enable innovative biotechnological approaches across diverse industries. By characterizing natural deep-sea chemosynthetic communities and applying genetic engineering to introduce these metabolisms into more tractable biological chassis, sustainable biomanufacturing, carbon capture, and bioremediation solutions can be developed. Both the molecules and mechanisms life has evolved to thrive in extreme chemical worlds offer a rich resource of inspiration for tackling global challenges with new kinds of engineered biology. With a greater scientific understanding of chemosynthesis, exciting opportunities may emerge in developing carbon-neutral bioprocesses, reimagining carbon recycling technologies, and designing the next generation of microbial ‘ecobots’ to help repair damaged environments.