The rhodopsin research has been one of the major topics in the biophysical research field for more than 40 years. The discovery of channelrhodopsin was only the product of the rhodopsin research, but the successful application of channelrhodopsin in neurons in the early 2000s has dramatically changed the strategy in neuroscience research afterwards. As a matter of fact, the new scientific term optogenetics is now widely accepted in the neuroscience and the optogenetic manipulation is an essential tool to develop the field. The author reviews the history of optogenetics.

Motility greatly benefits bacteria, e.g., nutrition, infection, and dissemination. Many bacterial species swim by rotating flagella outside the cell body. Although spirochetes are also flagellated bacteria, their flagella reside beneath the outer membrane. A distinct manner of spirochete motility attributed to the unique cell structure have intrigued many researchers, but detailed mechanism of how the intracellular flagella rotate the helical cell body and thereby generate thrust remains unknown. In this review, we outline the cell structure and motility of the spirochete Leptospira with a discussion of our recent results.

Collective movement and 3D morphogenesis are essential events in diverse physiological processes. We found that epithelial cells (MDCK cells) move collectively along one direction on a soft collagen gel, whereas the cells migrate randomly on a rigid collagen-coated-glass. Moreover, lumen formation occurred when an epithelial sheet on a collagen gel was overlaid with another collagen gel. We also found that MDCK cells formed 3D morphology on top of the Matrigel. The appearance of the morphologies was like a tulip hat. The cells tugged at the peripheral matrix and remodeled the gel surface. In this mini-review, these dynamical behaviors of the epithelial cells are discussed in terms of the cellular contractile force and viscoelasticity of the extracellular matrix.