1 Critical Reviews in Plant Sciences, 00(0):000–000 (2001) 0735-2689/01/$.50 © 2001 by CRC Press LLC Flagellar Movements and Controlling Apparatus in Flagellates Jacky Cosson, 1 Philippe Huitorel, 1 Laura Barsanti, 2 Patricia L. Walne, 3 and Paolo Gualtieri 2* 1 UMR7009 CNRS / UPMC, Observatoire Oceanologique, Station Zoologique, 06230 Villefranche-sur-mer, France; 2 Istituto di Biofisica, CNR, Area della Ricerca San Cataldo, via Moruzzi 1, 56127 Pisa, Italy; 3 Department of Botany, University of Tennessee, Knoxville, TN 37996-1100, USA * To whom correspondence and reprint requests should be addressed. Tel.: +39 050 315 3026 - fax: +39 050 315 2760 E-mail: paolo.gualtieri@ib.pi.cnr.it Referee: Dr. Kenneth R. Robinson, Department of Bilogical Sciences, Purdue University, West Lafayette, IN 47907-1392 ABSTRACT: Crawling, sliding, and swimming are only a few of the many motile responses of microorganisms to environmental cues. However, what is commonly defined as movement is just the final, often the only, detectable step of a series of complex intracellular reactions based on sophisticated locomotory machineries that function according to well-defined locomotory strategies and patterns. A simple motion can arise by a shape change of permanently linked molecules, and a more complex one by reversible interactions the causing movement of filaments relative to each other, or by reversible assembly and disassembly of elements, etc., all of which have in common the need for energy input. Proteins can undergo these changes in response to any modification of their environment and be considered the most likely molecules serving motor functions in real systems. The analysis of microrganism motors and motor controlling devices such as flagella and their accessory components suggests that the movement of these structures can be considered an example of propagation of sensory information along lattice-like structures by means of repetitive protein conformational changes. These intracellular devices taken as a whole could represent the network condensing both the information and motor systems in aneural microorgan- isms. KEY WORDS: locomotory devices, flagellum, accessory structures, paraflagellar rod, motion models. Table of Contents Introduction ....................................................................................................................... 4 Locomotory Patterns in microorganisms ................................................................................... 5 Motors ....................................................................................................................... 5 Swimming ....................................................................................................................... 6 Trajectory control ............................................................................................................ 8 Anatomy and Biochemistry of Controlling Devices ................................................................. 9 Flagellum ....................................................................................................................... 9 How a Flagellar Motor Works ...................................................................................... 10 Paraflagellar Rod ........................................................................................................... 11