Object Manipulation by a Formation-controlled Euglena Group

Itoh, Akitoshi; Tamura, Wataru

doi:10.1007/978-4-431-73380-5_4

Cited by 7 publications

(8 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Algae are also increasingly used in microbiomachine research, for example as micropropellers for the transport of colloidal cargo (38,39), where light can be used as the external driver of the motion. Although this research is yet to translate into practice, it represents an exciting avenue to harness microbial motility for controlled microscale applications, and phototaxis represents one of the most controllable processes because of the ease of accurately imposing and rapidly modulating external light gradients.…”

Section: Discussionmentioning

confidence: 99%

“…1 phytoplankton species that swims via an anterior flagellum and uses a paraflagellar body and red stigma (a red eyespot) (32) to respond to light gradients. E. gracilis has been used extensively as a model organism in both the ecological (33,34) and the ecophysiological literature (35,36) and has been used as a candidate species for technological applications such as photobioreactors (37) and micropropellers (38,39). We use the experimental results to identify a mathematical model for phototaxis.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis

Giometto

Altermatt

Maritan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to higher trophic levels in aquatic ecosystems. Phototaxis also finds important applications in biofuel reactors and microbiopropellers and is argued to serve as a benchmark for the study of biological invasions in heterogeneous environments owing to the ease of generating stochastic light fields. Despite its ecological and technological relevance, an experimentally tested, general theoretical model of phototaxis seems unavailable to date. Here, we present accurate measurements of the behavior of the alga Euglena gracilis when exposed to controlled light fields. Analysis of E. gracilis' phototactic accumulation dynamics over a broad range of light intensities proves that the classic Keller-Segel mathematical framework for taxis provides an accurate description of both positive and negative phototaxis only when phototactic sensitivity is modeled by a generalized "receptor law," a specific nonlinear response function to light intensity that drives algae toward beneficial light conditions and away from harmful ones. The proposed phototactic model captures the temporal dynamics of both cells' accumulation toward light sources and their dispersion upon light cessation. The model could thus be of use in integrating models of vertical phytoplankton migrations in marine and freshwater ecosystems, and in the design of bioreactors.phototactic potential | photoresponse | sensory system | photoaccumulation | microbial motility M icroorganisms possess a variety of sensory systems to acquire information about their environment (1), including the availability of resources, the presence of predators, and the local light conditions (2). For any sensory system, the system's response function determines the organism's capability to process the available information and turn it into a behavioral response. Such a response function is shaped by the natural environment and its fluctuations (3-5) and affects the search strategy [be it mate search, food search, etc. (6, 7)] and the swimming behavior of microorganisms (8). Gradient sensing is particularly important in marine and freshwater ecosystems, where the distribution of resources is highly heterogeneous (9, 10) and the ability to move toward resource hot spots can provide a strong selective advantage to motile organisms over nonmotile ones (2, 5). Spatiotemporal patterns of light underwater contribute to the heterogeneity of the aquatic environment. Because light is a major carrier of energy and information in the water column (11), phototaxis is a widespread case of directed gradient-driven locomotion (12, 13), found in many species of phytoplankton and zooplankton. Phototaxis strongly affects the ecology of aquatic ecosystems, contributing to diel vertical migration of phytoplankton, on...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis

Giometto

Altermatt

Maritan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Also the opposite has been found: cells swimming fast in the dark and slower in light will accumulate in the irradiated field (negative photokinesis). Another mechanism for cell accumulation is phototaxis of cells toward a light field irradiated by a strong light source such as a laser beam as shown for Euglena (Itoh and Tamura 2008).…”

Section: Introductionmentioning

confidence: 99%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

View full text Add to dashboard Cite

Motile microorganisms such as the green Euglena gracilis use a number of external stimuli to orient in their environment. They respond to light with photophobic responses, photokinesis and phototaxis, all of which can result in accumulations of the organisms in suitable habitats. The light responses operate synergistically with gravitaxis, aerotaxis and other responses. Originally the microscopically obvious stigma was thought to be the photoreceptor, but later the paraxonemal body (PAB, paraflagellar body) has been identified as the light responsive organelle, located in the trailing flagellum inside the reservoir. The stigma can aid in light direction perception by shading the PAB periodically when the cell rotates helically in lateral light, but stigmaless mutants can also orient with respect to the light direction, and negative phototaxis does not need the presence of the stigma. The PAB is composed of dichroically oriented chromoproteins which is reflected in a pronounced polarotaxis in polarized light. There was a long debate about the potential photoreceptor molecule in Euglena, including carotenoids, flavins and rhodopsins. This discussion was terminated by the unambiguous proof that the photoreceptor is a 400 kDa photoactivated adenylyl cyclase (PAC) which consists of two α- and two β-subunits each. Each subunit possesses two BLUF (Blue Light receptor Using FAD) domains binding FAD, which harvest the light energy, and two adenylyl cyclases, which produce cAMP from ATP. The cAMP has been found to activate one of the five protein kinase s found in Euglena (PK.4). This enzyme in turn is thought to phosphorylate proteins inside the flagellum which result in a change in the flagellar beating pattern and thus a course correction of the cell. The involvements of PAC and protein kinase have been confirmed by RNA interference (RNAi). PAC is responsible for step-up photophobic responses as well as positive and negative phototaxis, but not for the step-down photophobic response, even though the action spectrum of this resembles those for the other two responses. Analysis of several colorless Euglena mutants and the closely related Euglena longa (formerly Astasia longa) confirms the results. Photokinesis shows a completely different action spectrum. Some other Euglena species, such as E. sanguinea and the gliding E. mutabilis, have been investigated, again showing totally different action spectra for phototaxis and photokinesis as well as step-up and step-down photophobic responses.

show abstract

“…The setting position and angle were adjusted to examine taxis to blue light. By using a large number of Euglena, a mechanical assembly could be manipulated to perform the task of inserting the projection into the hole, both of which were made of planar plastic film [5].…”

Section: Introductionmentioning

confidence: 99%

Motion Control of Daphnia magna by Blue LED Light

Itoh

Hisama

2010

J. Abmech

Self Cite

View full text Add to dashboard Cite

Abstract-Daphnia magna show strong positive phototaxis to blue light. Here, we investigate the effectiveness of behavior control of D. magna by blue light irradiation for their use as bio-micromachines. D. magna immediately respond by swimming toward blue LED light sources. The behavior of individual D. magna was controlled by switching on the LED placed at 15° intervals around a shallow Petri-dish to give a target direction. The phototaxic controllability of Daphnia was much better than the galvanotactic controllability of Paramecium.

show abstract

Object Manipulation by a Formation-controlled Euglena Group

Cited by 7 publications

References 4 publications

Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis

Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis

Photomovement in Euglena

Motion Control of Daphnia magna by Blue LED Light

Contact Info

Product

Resources

About