Photomovement in Motile Microorganisms—ii

Nultsch, Wilhelm; Häder, Donat‐P.

doi:10.1111/j.1751-1097.1988.tb01668.x

Cited by 172 publications

(41 citation statements)

References 318 publications

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“…perpendicular to a light beam, Fig. 11.1c) has been found, a behavior called diaphototaxis (Häder and Lipson 1986;Nultsch and Häder 1988;Rhiel et al 1988). This behavior enables the organisms to swim horizontally at constant optimal light intensity.…”

Section: Introductionmentioning

confidence: 91%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

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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.

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Section: Introductionmentioning

confidence: 91%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

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“…in pelagic species and with substrate adhesion (stalks, tubes) and locomotion in benthic forms (Hoagland et al 1993). Many representatives of green algae possess cellulose or glycoprotein cell walls and capsules (van den Hoek et al 1995, Shubert 2003, several colonial forms are embedded in mucilage matrix, while mucilage is extruded by desmids for gliding (Nultsch & Hader 1988). In addition, many planktic forms release dissolved organic material, which comprises a significant fraction of polysaccharides (Kaplan 1987, Lombardi & Vieria 1999, Lombardi et al 2005.…”

Section: Introductionmentioning

confidence: 99%

Seasonal succession of phototrophic biofilms in an Italian wastewater treatment plant: biovolume, spatial structure and exopolysaccharides

Congestri

Pippo²,

Philippis³

et al. 2006

Aquat. Microb. Ecol.

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A multiphasic approach was applied to investigate the structural features of phototrophic biofilms that grow in a wastewater treatment plant (WWTP) at Fiumicino Airport (Rome, Italy). Seasonal variations in species composition, biomass and exopolysaccharides produced were analyzed by light (LM) and electron microscopy (SEM), high performance liquid chromatography (HPLC) and circular dichroism (CD). Phototroph contribution to the 3-dimensional structure of the biofilm and its development was assessed by confocal laser scanning microscopy. Analysis of biofilms grown on polypropylene slides showed a stable species composition; seasonal changes in biomass were mostly due to changes of major cyanobacterial and algal taxonomic groups. Extensive growth was evident on the range of artificial substrata that were implanted in the treatment plant. CD spectra and HPLC analyses of 2 operationally defined exopolysaccharide fractions extracted from samples scraped off the tank walls revealed that negatively charged heteropolysaccharides comprised most of the matrix and capsular components of the biofilms. Cytochemical staining distinguished between acidic and sulphated residues in the samples observed by LM. The data provide a new insight into the structural integrity and development of phototrophic biofilms in this hyper-eutrophic environment, indicating a potential use of autochthonous consortia in an environmentally sound tertiary water treatment alternative to conventional chemico-physical technologies.KEY WORDS: Phototrophic biofilms · Exopolysaccharides · Cyanobacteria · Algae · Biovolume · Confocal laser scanning microscope · Wastewater treatment plant Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 45: [301][302][303][304][305][306][307][308][309][310][311][312] 2006 and with substrate adhesion (stalks, tubes) and locomotion in benthic forms (Hoagland et al. 1993). Many representatives of green algae possess cellulose or glycoprotein cell walls and capsules (van den Hoek et al. 1995, Shubert 2003, several colonial forms are embedded in mucilage matrix, while mucilage is extruded by desmids for gliding (Nultsch & Hader 1988). In addition, many planktic forms release dissolved organic material, which comprises a significant fraction of polysaccharides (Kaplan 1987, Lombardi & Vieria 1999, Lombardi et al. 2005.Overall, EPS are involved in adhesion to the substrata and cohesion between the cells of a biofilm; they play a role in surface-associated motility and provide protection against desiccation and grazing by predators, producing a matrix network that embeds cells and detritus (Wingender et al. 1999, Decho 2000. These exopolymers provide a microenvironment where UVabsorbing pigments and proteins, including enzymes, are immobilized (Sutherland 2001). The major components of the matrix are polysaccharides, but proteins and nucleic acids can comprise a significant part (Decho 2000). Extracellular polysaccharides may also serve in the immobilization and accumula...

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“…Kinesis refers to a change in an organism's swimming speed or direction when exposed to external stimuli such as a chemical gradient (1), temperature gradient (2), and light (3). Of interest here is the gravikinesis exhibited by protozoa such as Paramecium, Didinium, and Loxodes (4-6).…”

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Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments

Guevorkian

Valles

2006

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

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Earth's gravity exerts relatively weak forces in the range of 10 -100 pN directly on cells in biological systems. Nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. A number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researching the underlying mechanisms. Here, we demonstrate a magnetic force-based technique that is unique in its capability to enhance, reduce, and even invert the effective buoyancy of cells and thus simulate hypergravity, hypogravity, and inverted gravity environments. We apply it to Paramecium caudatum, a single-cell protozoan that varies its swimming propulsion depending on its orientation with respect to gravity, g. In these simulated gravities, denoted by f gm, Paramecium exhibits a linear response up to fgm ‫؍‬ 5 g, modifying its swimming as it would in the hypergravity of a centrifuge. Moreover, experiments from f gm ‫؍‬ 0 to ؊5 g show that the response is symmetric, implying that the regulation of the swimming speed is primarily related to the buoyancy of the cell. The response becomes nonlinear for f gm >5 g. At fgm ‫؍‬ 10 g, many paramecia ''stall'' (i.e., swim in place against the force), exerting a maximum propulsion force estimated to be 0.7 nN. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.buoyancy ͉ force ͉ gravikinesis ͉ levitation ͉ microorganism

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Photomovement in Motile Microorganisms—ii

Cited by 172 publications

References 318 publications

Photomovement in Euglena

Photomovement in Euglena

Seasonal succession of phototrophic biofilms in an Italian wastewater treatment plant: biovolume, spatial structure and exopolysaccharides

Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments

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