Seeing Cell Division Like Never Before: A Breakthrough in Microscopy
Cell division is a fundamental process of life, but it is also a complex and dynamic one. How do cells manage to split into two identical copies while maintaining their shape and integrity? This question is especially challenging for bacteria that have two membranes, such as Escherichia coli and Salmonella. These bacteria have to coordinate the synthesis and constriction of both the inner and outer membranes, as well as the cell wall that lies between them.
Until recently, scientists had a limited view of how this process occurs, relying on conventional microscopy techniques that could only capture snapshots of the dividing cells. But now, researchers from Harvard Medical School have developed a novel method that combines fluorescent microscopy and cryo-electron tomography to reveal the three-dimensional structure and dynamics of double-membraned bacteria as they divide . This method allows them to visualize the changes in the membranes and the cell wall with unprecedented resolution and clarity.
The researchers used this method to study E. coli cells that were genetically modified to express fluorescent proteins that label the inner membrane, the outer membrane, and the cell wall. They first imaged the cells using fluorescent microscopy to identify the stage of division and then rapidly froze them in liquid nitrogen to preserve their structure. Next, they used cryo-electron tomography to obtain high-resolution images of the frozen cells from different angles, which they then reconstructed into 3D models using computational algorithms.
The results were stunning: they showed how the inner membrane constricts first, followed by the cell wall and then the outer membrane. They also revealed how the cell wall is synthesized and remodeled during division, and how the outer membrane proteins are distributed and rearranged. Furthermore, they discovered a new structure that forms at the division site, which they named the outer membrane constriction ring (OMCR). The OMCR is composed of densely packed proteins that may help stabilize and coordinate the constriction of the outer membrane.
The researchers hope that their method will open new avenues for studying bacterial cell division and other cellular processes that involve membrane dynamics. They also believe that their findings will have implications for understanding and combating antibiotic resistance, since many antibiotics target the cell wall or the membranes of bacteria. By revealing how these structures are formed and regulated during division, they may be able to identify new vulnerabilities and strategies for disrupting them.
Seeing cell division like never before is not only a scientific achievement, but also a visual delight. The images and videos produced by this method are captivating and mesmerizing, showing the beauty and complexity of life at the microscopic scale.