Chapter 3
Gravitaxis in Flagellates and Ciliates
Donat-Peter Häder and Ruth Hemmersbach
Abstract Motile microorganisms such as flagellates and ciliates use the gravity
vector of the Earth to adjust their position in the water column. Oriented movement
by gravity is called gravitaxis and can be positive (downward swimming) or negative
(upward swimming). In addition, some ciliates modify their velocity according to the
swimming direction (gravikinesis). Earth-bound research and experimentation under
simulated and real microgravity have revealed that a heavy mass such as a statolith
or the whole cell content presses onto a gravireceptor which perceives the signal.
In some cases mechanosensitive ion channels have been identified as gravireceptors.
The activation of the receptor results in a cascade of reactions which amplify the
signal and result in a steering response changing the direction of movement.
Keywords Ciliates · Flagellates · Gravitaxis · Gravikinesis · Mechanosensitive ion
channels · Sensory transduction chain
3.1 Introduction
Motile microorganisms such as flagellates and ciliates orient themselves with respect
to a number of physical and chemical factors in their environment to optimize the
conditions for growth and reproduction by using the light direction (phototaxis) for
vertical migrations in the water column (Fraenkel and Gunn 1961; Häder 1991;
Fiedler et al. 2005), the magnetic field of the Earth (magnetotaxis) (Simmons et al.
2004), thermal gradients (thermotaxis) (Maree et al. 1999) and chemical gradients of
attractants and repellents (chemotaxis) (Clegg et al. 2003; Wadhams and Armitage
2004).
Graviorientation has been studied in many motile microorganisms such as flagellates Tetraselmis, Dunaliella, Prorocentrum, Cryptomonas and Gymnodinium
(Rhiel et al. 1988; Eggersdorfer and Häder 1991; Richter et al. 2007) and ciliates
such as Paramecium, Tetrahymena, Bursaria, Stylonychia and Loxodes (Finlay et al.
1993; Hemmersbach and Donath 1995; Hemmersbach and Bräucker 2002), The
resulting vertical migrations produce pronounced phytoplankton distributions in
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_3
27
Gravitaxis in Flagellates and Ciliates
Donat-Peter Häder and Ruth Hemmersbach
Abstract Motile microorganisms such as flagellates and ciliates use the gravity
vector of the Earth to adjust their position in the water column. Oriented movement
by gravity is called gravitaxis and can be positive (downward swimming) or negative
(upward swimming). In addition, some ciliates modify their velocity according to the
swimming direction (gravikinesis). Earth-bound research and experimentation under
simulated and real microgravity have revealed that a heavy mass such as a statolith
or the whole cell content presses onto a gravireceptor which perceives the signal.
In some cases mechanosensitive ion channels have been identified as gravireceptors.
The activation of the receptor results in a cascade of reactions which amplify the
signal and result in a steering response changing the direction of movement.
Keywords Ciliates · Flagellates · Gravitaxis · Gravikinesis · Mechanosensitive ion
channels · Sensory transduction chain
3.1 Introduction
Motile microorganisms such as flagellates and ciliates orient themselves with respect
to a number of physical and chemical factors in their environment to optimize the
conditions for growth and reproduction by using the light direction (phototaxis) for
vertical migrations in the water column (Fraenkel and Gunn 1961; Häder 1991;
Fiedler et al. 2005), the magnetic field of the Earth (magnetotaxis) (Simmons et al.
2004), thermal gradients (thermotaxis) (Maree et al. 1999) and chemical gradients of
attractants and repellents (chemotaxis) (Clegg et al. 2003; Wadhams and Armitage
2004).
Graviorientation has been studied in many motile microorganisms such as flagellates Tetraselmis, Dunaliella, Prorocentrum, Cryptomonas and Gymnodinium
(Rhiel et al. 1988; Eggersdorfer and Häder 1991; Richter et al. 2007) and ciliates
such as Paramecium, Tetrahymena, Bursaria, Stylonychia and Loxodes (Finlay et al.
1993; Hemmersbach and Donath 1995; Hemmersbach and Bräucker 2002), The
resulting vertical migrations produce pronounced phytoplankton distributions in
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_3
27