Revisited Japanese research literature on the stalk contraction and relaxation of stalked ciliates

Sangjin RYU, Haipeng ZHANG, Moeto NAGAI
2021 Mechanical Engineering Reviews  
Revisited Japanese research literature on the stalk contraction and relaxation of stalked ciliates 1. Introduction Microorganisms have been actively studied as a model system for biomechanics and bioinspired engineering. In particular, the stalk contraction of stalked ciliates such as Vorticella, Carchesium and Zoothamnium (i.e., Vorticellidae) has long intrigued engineers and scientists because of its high contractile speed and unique energy source (Vincent 2000; Knoblauch & Peters 2004; Ryu
more » ... al. 2017; Soto et al. 2021 ). As Figure 1 shows, these sessile protozoa share the following common features. Each protozoan consists of single or multiple zooids (cell bodies), and a stalk or branched stalks. The stalk consists of a contractile fibrillar organelle called the spasmoneme, a robust sheath, the fibrillar matrix, and rod-like bundles of filaments called the bâtonnets. The spasmoneme runs through the entire length of the stalk as a helix whereas the bâtonnets run always located on the opposite side of the sheath from the spasmoneme. As the spasmoneme contracts, it takes a shorter path through the coil while the bâtonnets remain on the outside of the coil indicating the least deformable part of the sheath and stalk. Re-extension or relaxation of the stalk is thought to be driven by the elastic restoring force of the deformed sheath. The spasmoneme includes a major calcium ion (Ca 2+ )-binding protein, spasmin, and it contracts upon binding of calcium ions. For instance, the permeabilized stalk of V. convallaria coils when [Ca 2+ ] free > 10 −6 M whereas it remains extended when [Ca 2+ ] free < 10 −8 M. Here, [Ca 2+ ] free is the free Ca 2+ concentration of the medium (Ochiai Abstract This review paper revisits selected Japanese papers on the stalk contraction and relaxation of Vorticellidae. Vorticella, Carchesium and Zoothamnium have stalks that contract very fast powered by binding of calcium ions, and their stalks have the contractile organelle (spasmoneme) that includes nanoscale filaments and spasmin (the major calcium binding protein) in common. The stalk contraction of these Vorticellidae has been studied long for their ultrafast contraction, unique energy source and potential for bioinspired actuators. In particular, a significant amount of research was conducted by Japanese researchers for about one century. Although many of those studies were published in English and can be accessed by researchers around the world, some papers received very limited attentions despite their valuable findings and insights because they are written in Japanese. To make the key findings of such Japanese papers readily available, they are revisited and reviewed in this review paper. Papers on the stalk contraction and relaxation of Vorticella, Carchesium and Zoothamnium were found via J-STAGE, CiNii and Google Scholar, and six papers published between 1931 and 2006 were chosen, translated and reviewed for their findings and insights on the biomechanical aspects of stalk contraction and relaxation. Also, chosen figures of the papers were re-worked for better readability, and selected data were analyzed further. Revisiting these Japanese papers is meaningful to research communities on biomechanical engineering, bioinspired engineering and biophysics.
doi:10.1299/mer.21-00252 fatcat:nb4mxtcpxrctzo7f74oeaog5l4