Final Project - Ideas/Drafts

Project Idea:

Developing an Engineerable Photogranule System for Wastewater Treatment with Cyanobacterium Oscillatoria sp. and Chassis Bacterium Acinetobacter baylyi ADP1

Effective wastewater treatment is essential for human and environmental health. However, conventional treatment methods are energy-intensive, resource-intensive, and produce a nutrient and pollutant-rich “sludge” byproduct that is usually disposed of via incineration or dumping into landfills. These methods release greenhouse gases into the atmosphere and contaminate soil and aquatic ecosystems with toxic, eutrophication-inducing waste.

Oxygenic photogranules, glob-like consortia of filamentous photosynthetic cyanobacteria and non-photosynthetic bacteria, naturally absorb and break down harmful chemicals (Wang et al., 2023; Atoku et al, 2021) and offer several sustainability advantages over current wastewater treatment techniques (Brockmann et al., 2021). Unlike conventional methods, which involve oxygen-dependent bacteria, a photogranule system would be self-oxygenating—eliminating the need for an energy-intensive aeration process (Abouhend et al., 2018; Milferstedt et al., 2017), self-aggregating—potentially reducing the need for chemical flocculants (Smetana et al., 2023), and renewable: cyanobacteria fix nitrogen and phosphorous, and resulting photogranular “sludge” could be sustainably repurposed as fertilizer or biofuel (Trebuch et al., 2024).

I aim to develop an engineerable model photogranule system that could be easily modified (via genetic engineering techniques) to enhance versatility and resilience to diverse microbial conditions, target specific chemical products and pollutants of-interest for removal and/or detoxification, and enhance the viability of the bacterial-waste sludge for renewable downstream applications. My project will use Oscillatoria sp., a photogranule-forming cyanobacterium that I currently culture in the W&M Bioengineering Lab, and Acinetobacter baylyi ADP1, a highly-engineerable non-photosynthetic model bacterium with natural pollutant-degradation capabilities and promising applications in biosensing and bioremediation (Baugh et al., 2025; Li et al., 2021; Cui et al., 2018; Suárez et al., 2017). I plan to enhance A. baylyi’s ability to associate and form photogranules with Oscillatoria by upregulating genetic pathways associated with biofilm formation and aggregation and by modifying the structure of certain membrane proteins so that they adhere to molecules in Oscillatoria’s cellular secretions. My Oscillatoria-Acinetobacter photogranules will be easily-engineerable via the well-characterized model A. baylyi, providing a platform for future photogranule-based biotechnology applications.

References

Abouhend, A. S., McNair, A., Kuo-Dahab, W. C., Watt, C., Butler, C. S., Milferstedt, K., Hamelin, J., Seo, J., Gikonyo, G. J., El-Moselhy, K. M., & Park, C. (2018). The Oxygenic Photogranule Process for Aeration-Free Wastewater Treatment. Environmental Science & Technology, 52(6), 3503–3511. https://doi.org/10.1021/acs.est.8b00403

Atoku, D. I., Ojekunle, O. Z., Taiwo, A. M., & Shittu, O. B. (2021). Evaluating the efficiency of Nostoc commune, Oscillatoria limosa and Chlorella vulgaris in a phycoremediation of heavy metals contaminated industrial wastewater. Scientific African, 12, e00817. https://doi.org/10.1016/j.sciaf.2021.e00817

Baugh, A. C., Tumen-Velasquez, M. P., Zempel, I. R., Duscent-Maitland, C. V., Slarks, L. E., Defalco, J. B., Johnson, C. W., Beckham, G. T., & Neidle, E. L. (2025). Rewiring Aromatic Compound Consumption: Chromosomal Amplification and Evolution of a Foreign Pathway in Acinetobacter baylyi ADP1. ACS Synthetic Biology, 14(9), 3543–3556. https://doi.org/10.1021/acssynbio.5c00341

Brockmann, D., Gérand, Y., Park, C., Milferstedt, K., Hélias, A., & Hamelin, J. (2021). Wastewater treatment using oxygenic photogranule-based process has lower environmental impact than conventional activated sludge process. Bioresource Technology, 319, 124204. https://doi.org/10.1016/j.biortech.2020.124204

Cui, Z., Luan, X., Jiang, H., Li, Q., Xu, G., Sun, C., Zheng, L., Song, Y., Davison, P. A., & Huang, W. E. (2018). Application of a bacterial whole cell biosensor for the rapid detection of cytotoxicity in heavy metal contaminated seawater. Chemosphere, 200, 322–329. https://doi.org/10.1016/j.chemosphere.2018.02.097

Li, H., Yang, Y., Zhang, D., Li, Y., Zhang, H., Luo, J., & Jones, K. C. (2021). Evaluating the simulated toxicities of metal mixtures and hydrocarbons using the alkane degrading bioreporter Acinetobacter baylyi ADPWH_recA. Journal of Hazardous Materials, 419, 126471. https://doi.org/10.1016/j.jhazmat.2021.126471

Milferstedt, K., Kuo-Dahab, W. C., Butler, C. S., Hamelin, J., Abouhend, A. S., Stauch-White, K., McNair, A., Watt, C., Carbajal-González, B. I., Dolan, S., & Park, C. (2017). The importance of filamentous cyanobacteria in the development of oxygenic photogranules. Scientific Reports, 7(1), 17944. https://doi.org/10.1038/s41598-017-16614-9

Smetana, G., & Grosser, A. (2023). The Oxygenic Photogranules—Current Progress on the Technology and Perspectives in Wastewater Treatment: A Review. Energies, 16(1), 523. https://doi.org/10.3390/en16010523

Suárez, G. A., Renda, B. A., Dasgupta, A., & Barrick, J. E. (2017). Reduced Mutation Rate and Increased Transformability of Transposon-Free Acinetobacter baylyi ADP1-ISx. Applied and Environmental Microbiology, 83(17), e01025-17. https://doi.org/10.1128/AEM.01025-17

Trebuch, L. M., Timmer, J., Graaf, J. V. D., Janssen, M., & Fernandes, T. V. (2024). Making waves: How to clean surface water with photogranules. Water Research, 260, 121875. https://doi.org/10.1016/j.watres.2024.121875

Wang, Z., Chen, W., Wang, J., Gao, M., Zhang, D., Zhang, S., Hao, Y., & Song, H. (2023). Exploring the mechanism and negentropy of photogranules for efficient carbon, nitrogen and phosphorus recovery from wastewater. Chemical Engineering Journal, 476, 146510. https://doi.org/10.1016/j.cej.2023.146510