The Long Awaited Pursuit of Scientists: Cryo-EM

Written by Aayushi Bhattarai

In the fight against infectious diseases, understanding how pathogens move, invade, and resist treatment is one of the most pressing challenges in microbiology. Understanding such behaviors will enable us to tailor our treatments based on their specific characteristics. With a more specific understanding of pathogens’ behavior, we can also create solutions that target their exact behaviors.

So what if I told you that there is technology that can reach this level of precision?

I would like to introduce you to (or perhaps re-introduce you to) Cryo-electron microscopy (Cryo-EM), a revolutionary imaging technique. Cryo-Em is currently transforming this pursuit (understanding pathogens behavior with a level of high specificity) by allowing scientists to visualize pathogens and their molecular machinery at near-atomic resolution.

Nobel Prize Winners Jacques Dubochet, Joachim Frank, and Richard Henderson developed Cryo-em (THE ROYAL SWEDISH ACADEMY OF SCIENCES, 2017). The development of Cryo-em started when George Gamow, a well-known physicist, published a book titled Mr Tompkins Inside Himself: Adventures in the New Biology.

In the novel, the protagonist Mr. Tompkins explores the cellular makeup of his body on a “dream” journey through his bloodstream with his doctors assisting during the journey. This book demonstrated the ultimate goal of what scientists wanted to achieve in technology, specifically microscopy.

With the electron microscope, scientists would be able to understand atomic details of biomolecules with extremely high precision and specificity. Such specificity would underpin their architecture, and day-to-day functions; remarkably useful information for research and understanding of how biomolecules interact with each other.

Cryo-em deviates from traditional microscopy, which often struggles to capture delicate biological structures without distortion. Cryo-EM flash-freezes specimens in near-native form so that scientists can observe viral envelopes, bacterial efflux pumps (protein transporters in cell membranes that actively pump substances, such as toxic compounds, drugs, and other waste, out of the cell), and resistance-conferring protein complexes with unprecedented clarity (Cabra & Samsó, 2015). Using this technology, microbiologists are endowed with a window to the mechanisms that underpin both transport and resistance in pathogens.

Recent studies have utilized Cryo-EM’s abilities to resolve the architecture of multidrug efflux pumps in Gram-negative bacteria, revealing how these molecular machines actively expel antibiotics before they can act.

Similarly, Cryo-EM has shed light on how viral proteins reshape host membranes during entry, transport, and replication steps, which are often key targets for antiviral therapies. Bringing structural biology and microbiology, Cryo-EM gains a potential that allows scientists the ability to design inhibitors, which can block transport pathways or disable resistance mechanisms.

More recently, advancements in cryo-electron tomography (Cryo-ET) have pushed these capabilities further, enabling imaging of entire bacterial cells at nanometer resolution within a single dataset, providing unprecedented insight into their intricate molecular nanomachines (Söderholm et al., 2020).

This comprehensive view has transformed our understanding of bacterial and archaeal cells from simple “bags of small molecules” to complex macromolecular machinery (Oikonomou & Jensen, 2021). This technical leap allows researchers to observe cellular components in their native state, avoiding artifacts introduced by conventional staining or dehydration methods.

Ultimately, Cryo-EM provides the indispensable lens for unraveling the fundamental mechanisms of life and disease. This profound mechanistic insight is crucial for developing targeted interventions and pioneering novel therapeutic strategies against a broad spectrum of infectious agents.

References:

1. Cabra, V., & Samsó, M. (2015). Do’s and Don’ts of Cryo-electron Microscopy: A Primer on Sample Preparation and High Quality Data Collection for Macromolecular 3D Reconstruction. Journal of Visualized Experiments, 95. https://doi.org/10.3791/52311
2. Oikonomou, C. M., & Jensen, G. J. (2021). The Atlas of Bacterial & Archaeal Cell Structure : an Interactive Open-Access Microbiology Textbook. Journal of Microbiology & Biology Education, 22(2). https://doi.org/10.1128/jmbe.00128-21
3. Söderholm, N., Singh, B., Uhlin, B. E., & Sandblad, L. (2020). Exploring the bacterial nano-universe. Current Opinion in Structural Biology, 64, 166–173. https://doi.org/10.1016/j.sbi.2020.07.002
4. THE ROYAL SWEDISH ACADEMY OF SCIENCES. (2017). Nobel Prize ® and the Nobel Prize ® medal design mark are registered trademarks of the Nobel Foundation Scientific Background on the Nobel Prize in Chemistry 2017 THE DEVELOPMENT OF CRYO-ELECTRON MICROSCOPY. https://www.nobelprize.org/uploads/2018/06/advanced-chemistryprize2017.pdf