Towards an Engineered, Self-Sustained Microbial Ecosystem

Life on earth does not need any input apart from the energy provided through sunlight, and maintains itself by the cycling of nutrients. The sunlight is converted into chemical energy by photosynthetic plants and algae, which in turn provide food to other, non-photosynthetic organisms, i.e. heterotrophs. We are currently engineering a similarly self-sufficient and light-driven microbial ecosystem with tailored capabilities for chemical conversions. This will serve a dual purpose; the resulting engineered ecosystem will serve as a model system to better understand complex natural microbial communities, and at the same time, it is a novel low-cost system for the biotechnological production of value-added chemicals.

Communities of algae and bacteria are widespread in nature and are promising for applications as wastewater treatment and production of value added chemicals such as biofuels.¹ They are advantageous over single bacterial strains since they can work in cooperative ways. Multiple steps of a chemical synthesis can be compartmentalised among different bacteria, which reduces the energy-investment (and hence metabolic burden) for each individual cell.^2,3 Furthermore the community members support each other’s growth by clearing up toxic metabolic side-products^3–5 and providing growth factors such as vitamins.⁶ As an example, the superiority of a synthetic community was demonstrated by the efficient degradation of chemical contaminants associated with oil spills, while the individual organisms were less or not capable to degrade these compounds.^7,8

To exploit microbial communities, it is necessary to gain a fundamental understanding of how and why microbes interact, and how such interactions react to disturbances.⁹ Answering these questions in natural systems is almost impossible due to their sheer complexity and limitations on performing controlled experiments. Thus, we are engineering a minimalist self-sustained microbial ecosystem, which can maintain itself over extended time-scales, hence facilitating the investigation of interactions between the community members. The applicability of this ecosystem to chemical synthesis will be examined by creating a biomineralisation-cycle within the community, which allows the production of manganese oxide, a reactive mineral with significant potential in biodegradation and conversion of organic wastes into high-value chemicals.¹⁰ This knowledge will support the bottom-up design of light-driven bacterial communities with desired synthetic capabilities, but also give new insights into natural microbial communities with a defined engineered model-ecosystem.

References

(1)     Ramanan, R. et al. Biotechnol. Adv. 2015.

(2)     Zhou, K. et al. Nat. Biotechnol. 2015, 33 (4), 377–383.

(3)     Kouzuma, A.; Kato, S.; Watanabe, K. Front. Microbiol. 2015, 6, 477.

(4)     Christie-Oleza, J. A.; Scanlan, D. J.; Armengaud, J. Proteomics 2015, 15 (20), 3454–3462.

(5)     Großkopf, T.; Soyer, O. S. Curr. Opin. Microbiol. 2014, 18, 72–77.

(6)     Amin, S. A.; Parker, M. S.; Armbrust, E. V. Microbiol. Mol. Biol. Rev. 2012, 76 (3), 667–684.

(7)     Tang, X. et al. J. Hazard. Mater. 2010, 181 (1-3), 1158–1162.

(8)     Abed, R. M. M.; Köster, J. Int. Biodeterior. Biodegradation 2005, 55 (1), 29–37.

(9)     Goers, L.; Freemont, P.; Polizzi, K. M. J. R. Soc. Interface 2014, 11 (96), 20140065.

(10)      Remucal, C. K.; Ginder-Vogel, M. Environ. Sci. Process. Impacts 2014, 16 (6), 1247–1266.