The kinky propulsion of Spiroplasma

Transcription

1 The kinky propulsion of Spiroplasma Anna Tuttle Microbiology Journal Club October 13, 2008

2 How do bacteria move? Flagellar helical propellor driven by rotary motor Some, like Spirochetes, have internal flagellum Twitching extension and retraction of Type IV pili Gliding slime secretion pushes the cell forward

3 All About Spiroplasma Genus of Mollicutes No cell wall Cell membrane has cholesterol Internal cytoskeleton Helical structure Descendents of Gram-positives Very small genomes Mb

4 All About Spiroplasma Insect, plant, tick, crustacean hosts Plant diseases Citris stubborn disease Corn stunt disease Many in obligate insect/ plant transmission cycles

5 All About Spiroplasma Insect diseases Sex-ratio abnormality in Drosophila Suckling mouse cataract agent Cause millions in damage in CA alone Difficult to treat

6 All About Spiroplasma 1972, found to be causative agent of Corn Stunt Disease Found to be helical, motile, and representative of new group of pathogens

7 How do Spiroplasma move?

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9 How do Spiroplasma move? Regular extension and contraction within limits of helical symmetry Spontaneous and random change of helical sense originating at random sites along the cell Forming a deformation on one of the helical turns and propagating it along the cell Random bending, flexing, and twitching

10 How do Spiroplasma move? Regular extension and contraction within limits of helical symmetry Spontaneous and random change of helical sense originating at random sites along the cell Forming a deformation on one of the helical turns and propagating it along the cell Random bending, flexing, and twitching

11 How do Spiroplasma move? Regular extension and contraction within limits of helical symmetry Spontaneous and random change of helical sense originating at random sites along the cell Forming a deformation on one of the helical turns and propagating it along the cell Random bending, flexing, and twitching

12 How do Spiroplasma move? Regular extension and contraction within limits of helical symmetry Spontaneous and random change of helical sense originating at random sites along the cell Forming a deformation on one of the helical turns and propagating it along the cell Random bending, flexing, and twitching

13 How do Spiroplasma move? Regular extension and contraction within limits of helical symmetry Spontaneous and random change of helical sense originating at random sites along the cell Forming a deformation on one of the helical turns and propagating it along the cell Random bending, flexing, and twitching

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15 Filamentous Structures Underneath the Cell Membrane Thick and thin filaments arranged in parallel Anchored to the cell membrane Run the length of the cell

16 Determining the Number and Spacing of Individual Filaments Outer ribbons 5 thick filaments 11 nm spacing Inner ribbon 9 thin filaments 4 nm spacing

17 Ribbon Arrangement Through the Cell Ribbons (red and green) follow helical path from one end to the other One shorter than the other Simultaneous conformational changes of adjacent filament subunits Leads to helicity and ability to change handedness

18 How the Cytoskeleton Enables Movement Assumptions: Ribbons connected to each other Inner thin filament ribbon functions elastically Filament length changes of outer ribbons occur simultaneously by switching between 2 conformational states of filament subunits

19 How the Cytoskeleton Enables Movement One ribbon becomes tense by shortening while the other relaxes Handedness switches at position where state of tension and relaxation reverses That point of transition travels the length of the cell

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21 Pathogenesis is linked to the ability of an infectious organism to move around. If we understand how a pathogen moves, we can figure out how to disrupt its movements and decrease its ability to infect other organisms. --- Joshua Shaevitz

22 Swimming driven by propagafon of kinks down body of cell

23 Cells and Kink PosiFons Over Time

24 Cell Swimming Parameters

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26 Conclusions Propulsion by waves of lateral displacement that propagate down the length of the cell Waves created by change in handedness of the cell body that creates 111 bend Swimming uses bistable helical cytoskeleton New method for movement

27 QuesFons?