Euglena, a Gravitactic Flagellate of Multiple Usages

Abstract

Human exploration of space and other celestial bodies bears a multitude of challenges. The Earth-bound supply of material and food is restricted, and in situ resource utilisation (ISRU) is a prerequisite. Excellent candidates for delivering several services are unicellular algae, such as the space-approved flagellate Euglena gracilis. This review summarizes the main characteristics of this unicellular organism. Euglena has been exposed on various platforms that alter the impact of gravity to analyse its corresponding gravity-dependent physiological and molecular genetic responses. The sensory transduction chain of gravitaxis in E. gracilis has been identified. The molecular gravi-(mechano-)receptors are mechanosensory calcium channels (TRP channels). The inward gated calcium binds specifically to one of several calmodulins (CaM.2), which, in turn, activates an adenylyl cyclase. This enzyme uses ATP to produce cAMP, which induces protein kinase A, followed by the phosphorylation of a motor protein in the flagellum, initiating a course correction, and, finally, resulting in gravitaxis. During long space missions, a considerable amount of food, oxygen, and water has to be carried, and the exhaled carbon dioxide has to be removed. In this context, E. gracilis is an excellent candidate for biological life support systems, since it produces oxygen by photosynthesis, takes up carbon dioxide, and is even edible. Various species and mutants of Euglena are utilized as a producer of commercial food items, as well as a source of medicines, as it produces a number of vitamins, contains numerous trace elements, and synthesizes dietary proteins, lipids, and the reserve molecule paramylon. Euglena has anti-inflammatory, -oxidant, and -obesity properties.

Changes in Gravitaxis and Gene-Expression in an Euglena gracilis Culture over Time

“…E. gracilis is a promising component for life support systems in space research and has already been employed in space experiments [ 4 ]. With E. gracilis as an intrinsic part of a long-term closed biological life support system, it was possible to grow tomatoes from seed to seed [ 48 ].…”

“…Physiological downstream events of cAMP modulation are yet unclear. Gravitaxis was found to be (at least partially) controlled by active physiological signal transduction mechanisms, in which, among others, mechanosensitive ion channels, calcium, cAMP, calmodulin, and protein kinases are involved [ 4 ].…”

Water quality assessment of river based on phytoplankton biological integrity index in rural areas of the upstream Citarum River, West Java, Indonesia

“…Their mixotrophic nutrition allows Euglena to utilize diverse carbon sources, combining photosynthesis and heterotrophic feeding, including organic compounds in polluted waters (Inwongwan et al 2019;Ilham et al 2020). The organism's motility, facilitated by a flagellum, enables active movement, allowing Euglena to navigate from areas with high pollutant concentrations (Häder and Hemmersbach 2022). Additionally, Euglena can form protective cysts during unfavorable conditions, contributing to its resilience (Roy et al 2014).…”

Planktonic Active Matter

“…Gravitactic species a H. akashiwo, b Chamydomonas reinhardtii (image adapted from Ref. [35]), both imaged in phase contrast mode, c scanning electron micrograph of ciliate Paramecium tetraurelia [36], and d brightfield image of Euglena gracilis [37]. F1 and F2 indicate the flagella present in the corresponding species.…”