title: Motion analysis and ultrastructural study of a colonial diatom, Bacillaria paxillifer.
abstract: The pennate diatom, Bacillaria paxillifer, forms a colony in which adjacent cells glide smoothly and almost continuously, yet no obvious apparatus driving the movement, such as flagella or cilia, is observed. Thus far, neither the mechanism nor physiological significance of this movement has been well understood. Here, we report quantitative analysis of the gliding motion of B. paxillifer and morphological analysis of this diatom with light and electron microscopes. The gliding of pairs of adjacent B. paxillifer cells in a colony was cyclic with rather constant periods while the average gliding period varied from a few seconds to multiples of 10 s among colonies. The gliding was compromised reversibly by inhibitors for actin and myosin, suggesting involvement of the actomyosin system. Indeed, we observed two closely apposed actin bundles near the raphe by fluorescence-labeled phalloidin staining. Using electron microscopy, we observed filamentous structures that resemble the actin bundles seen with fluorescence microscopy, and we also found novel electron-dense structures located between the plasma membrane and these actin-like filaments. From these and other observations, we suggest that B. paxillifer also uses actin bundles and propose a putative myosin as a molecular motor in the gliding of unicellular diatoms.
authors.affiliation: Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Yamaoka
authors.affiliation: Iwakuni City Microlife Museum, Arakeura, Yuu-machi, Iwakuni-shi, Yamaguchi 740-1488, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Suetomo
authors.affiliation: Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Yoshihisa
authors.affiliation: Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan sonobe@sci.u-hyogo.ac.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Sonobe
mesh_terms: D008841:Actin Cytoskeleton; D000199:Actins / Q000037:antagonists & inhibitors; D000205:Actomyosin / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology*; D003572:Cytochalasins / Q000494:pharmacology; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D017377:Diatoms / Q000502:physiology* / Q000648:ultrastructure*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D020409:Molecular Motor Proteins / Q000378:metabolism; D009068:Movement / Q000502:physiology*; D009218:Myosins / Q000037:antagonists & inhibitors; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003572:Cytochalasins; D004791:Enzyme Inhibitors; D020409:Molecular Motor Proteins; D053778:Thiazolidines; C031218:cytochalasin A; C004717:diacetylmonoxime; D000205:Actomyosin; D009218:Myosins; D003931:Diacetyl; C037067:latrunculin A
keywords: Bacillaria paxillifer; actin; diatom; gliding; myosin; ultrastructure