Influence of accelerations on the spatial orientation of Loxodes and Paramecium

Hemmersbach, Ruth; Voormanns, Regine; Briegleb, W.; Rieder, Norbert; Häder, Donat‐P.

doi:10.1016/0168-1656(96)01337-5

Cited by 37 publications

(11 citation statements)

References 18 publications

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“…46 In real and simulated microgravity, Loxodes loses its orientation behavior and swims in random directions. The threshold for gravitaxis was found at 0.16 g. 44 …”

Section: Introductionmentioning

confidence: 92%

“…Negative gravitaxis under terrestrial conditions and loss of gravitaxis in real and simulated microgravity have extensively been studied, and a threshold for gravitaxis on the order of 0.3 g has been determined by using a centrifuge microscope in space. 44 Like Euglena , Paramecium (around four times larger than Euglena ) uses the heavy cellular content to detect gravity by a physiological mechanism. It is assumed that the pressure of the cell mass activates mechanosensitive ion channels in the outer membrane.…”

Section: Introductionmentioning

confidence: 99%

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Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

et al. 2017

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We have selected five evolutionary very different biological systems ranging from unicellular protists via algae and higher plants to human cells showing responses to the gravity vector of the Earth in order to compare their graviperception mechanisms. All these systems use a mass, which may either by a heavy statolith or the whole content of the cell heavier than the surrounding medium to operate on a gravireceptor either by exerting pressure or by pulling on a cytoskeletal element. In many cases the receptor seems to be a mechanosensitive ion channel activated by the gravitational force which allows a gated ion flux across the membrane when activated. This has been identified in many systems to be a calcium current, which in turn activates subsequent elements of the sensory transduction chain, such as calmodulin, which in turn results in the activation of ubiquitous enzymes, gene expression activation or silencing. Naturally, the subsequent responses to the gravity stimulus differ widely between the systems ranging from orientational movement and directed growth to physiological reactions and adaptation to the environmental conditions.

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“…46 In real and simulated microgravity, Loxodes loses its orientation behavior and swims in random directions. The threshold for gravitaxis was found at 0.16 g. 44 …”

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

et al. 2017

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“…A Müller organelle consists of a heavy body of barium sulfate fixed to a modified ciliary complex. Their function as mechanoreceptors (statocyst-like organelles) has been proposed and studied by Penard (1917), Fenchel andFinlay (1986), Hemmersbach et al (1996Hemmersbach et al ( , 1998 and Neugebauer et al (1998). The specific density of the barium sulfate particles has been determined to be 4.4 g/mL (Hemmersbach et al 1998).…”

Section: Plants and Animalsmentioning

confidence: 98%

Gravitaxis in Euglena

Häder

Hemmersbach

2017

Advances in Experimental Medicine and Biology

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Motile microorganisms utilize a number of responses to external stimuli including light, temperature, chemicals as well as magnetic and electric fields. Gravity is a major clue to select a niche in their environment. Positive gravitaxis leads an organism down into the water column and negative gravitaxis brings it to the surface. In Euglena the precision of gravitaxis is regulated by an internal rhythm entrained by the daily light/dark cycle. This and the cooperation with phototaxis bring the cells into an optimal position in the water column. In the past a passive orientation based on a buoy mechanism has been proposed for Euglena gracilis, but now it has been proven that this flagellate possesses a physiological gravireceptor and an active orientation. Numerous experiments in space using satellites, rockets and shuttles as well as in parabolic flights have been conducted as well as in functional weightlessness (simulated microgravity) on ground-based facilities such as clinostats to characterize the gravitaxis of Euglena. The threshold for gravity perception was determined and physiological, biochemical and molecular components of the signal transduction chain have been identified. In contrast to higher plants, some algae and ciliates, Euglena does not possess sedimenting statoliths to detect the direction of the gravity vector of the Earth. The gravireceptors were found to be mechano-sensitive Ca-conducting ion channels thought to be located at the front end of the cell underneath the trailing flagellum. When activated by gravity-induced pressure due to sedimentation of the whole cell body, they allow a passive influx of calcium along a previously established ion gradient. The entering calcium binds to a specific calmodulin (CaM.2) which in turn activates an adenylyl cyclase producing cAMP from ATP. This cAMP is believed to activate a specific protein kinase A (PK.4), which is postulated to phosphorylate proteins inside the flagellum resulting in a bending and thus a course correction and reorientation with respect to the direction of the gravity vector. The elements of the signal transduction chain have been characterized by inhibitors and by RNAi to prove their involvement in gravitaxis.

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“…When prodded in the posterior they accelerate away and when prodded in the anterior they perform an avoiding reaction, backing up to swivel off in a new swimming direction [14,15]. We address whether their collisions with nearly planar surfaces evoke similar active changes in propulsion.Paramecia are among the many microorganisms small enough that their motion occurs at low Reynolds number (Re) but large enough that their apparent weight,w, influences their swimming [16][17][18][19][20][21][22][23][24][25][26]. This combination indicates that surface collision forces might be large enough to provoke an active response.…”

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confidence: 99%

“…They also exhibit negative gravikinesis by exerting a stronger propulsive force when swimming against their apparent weight [32][33][34]. Both behaviors disappear when Paramecia are neutrally buoyant [30,35]. The gravitactic response appears to be a passive response to a mechanical torque arising from an asymmetry of the Paramecium body [29].…”

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confidence: 99%

Trapping of Swimming Microorganisms at Lower Surfaces by Increasing Buoyancy

2014

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Models suggest that mechanical interactions alone can trap swimming microorganisms at surfaces. Testing them requires a method for varying the mechanical interactions. We tuned contact forces between Paramecia and surfaces in situ by varying their buoyancy with nonuniform magnetic fields. Remarkably, increasing their buoyancy can lead to ∼100% trapping at lower surfaces. A model of Paramecia in surface contact passively responding to external torques quantitatively accounts for the data implying that interactions with a planar surface do not engage their mechanosensing network and illuminating how their trapping differs from other smaller microorganisms.

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Influence of accelerations on the spatial orientation of Loxodes and Paramecium

Cited by 37 publications

References 18 publications

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

Gravitaxis in Euglena

Trapping of Swimming Microorganisms at Lower Surfaces by Increasing Buoyancy

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