Photomovement of Motile Microorganisms

Nultsch, Wilhelm; Häder, Donat‐P.

doi:10.1111/j.1751-1097.1979.tb07072.x

Cited by 91 publications

(29 citation statements)

References 185 publications

(140 reference statements)

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“…Photokinetic cyanobacteria move at different speeds controlled by light conditions (24). The diameters of cable bacteria varied from 0.4 to 2.2 m, and there was no correlation between diameter and speed ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Motility of Electric Cable Bacteria

Bjerg

Damgaard

Holm

et al. 2016

Appl Environ Microbiol

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Cable bacteria are filamentous bacteria that electrically couple sulfide oxidation and oxygen reduction at centimeter distances, and observations in sediment environments have suggested that they are motile. By time-lapse microscopy, we found that cable bacteria used gliding motility on surfaces with a highly variable speed of 0.5 ؎ 0.3 m s ؊1 (mean ؎ standard deviation) and time between reversals of 155 ؎ 108 s. They frequently moved forward in loops, and formation of twisted loops revealed helical rotation of the filaments. Cable bacteria responded to chemical gradients in their environment, and around the oxic-anoxic interface, they curled and piled up, with straight parts connecting back to the source of sulfide. Thus, it appears that motility serves the cable bacteria in establishing and keeping optimal connections between their distant electron donor and acceptors in a dynamic sediment environment. IMPORTANCEThis study reports on the motility of cable bacteria, capable of transmitting electrons over centimeter distances. It gives us a new insight into their behavior in sediments and explains previously puzzling findings. Cable bacteria greatly influence their environment, and this article adds significantly to the body of knowledge about this organism.

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Section: Resultsmentioning

confidence: 99%

Motility of Electric Cable Bacteria

Bjerg

Damgaard

Holm

et al. 2016

Appl Environ Microbiol

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“…The older literature has been reviewed (Haupt 1959;Feinleib and Curry 1967;Diehn 1973;Nultsch 1975;Nultsch and Häder 1979). Photophobic responses are elicited by rather sudden changes in irradiance.…”

Section: Photophobic Responsesmentioning

confidence: 98%

“…This behavior will result in an accumulation of cells in the irradiated area over time. This reaction is exploited in the socalled light trap method used to quantify photophobic responses (Nultsch and Häder 1979). Likewise, a sudden increase in the ambient light intensity may result in a step-up photophobic response which is elicited by a sudden increase in light intensity which would occur when an organism enters a irradiated area from a shaded one (Doughty and Diehn 1984;Ntefidou et al 2003b;Takeda et al 2013).…”

Section: Introductionmentioning

confidence: 98%

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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“…There has been interest and controversy for many years about whether free-swimming phototrophic bacteria can sense the direction of light as well as its intensity, i.e., whether they show true phototaxis (3,4,12,14). It is well-known that phototrophic bacteria, including Chromatium, Rhodospirillum, and Thiospirillum spp., reverse direction when swimming through a light/dark boundary, causing them to be trapped on the light side of the boundary (reviewed in reference 6).…”

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confidence: 99%

“…This system allowed us to assay all these possibilities under the controlled conditions of a microscope slide. As a control, we also examined the behavior of the alga Chlamydomonas reinhardtii (which is known to exhibit true phototaxis) (14,19).…”

mentioning

confidence: 99%

Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

et al. 1997

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We have measured the photoresponse of two purple nonsulfur bacteria, Rhodobacter sphaeroides and Rhodospirillum centenum, under defined conditions in a light beam propagating at 90°to the optical axis of the microscope. This beam presented cells with a steep gradient of intensity perpendicular to the direction of propagation and a shallow gradient in the direction of light propagation. R. centenum, a species that reverses to change direction, accumulated in the light beam, as expected for a "scotophobic" response, while R. sphaeroides, which stops rather than reverses, accumulated outside the light beam. We also compared the behavior of liquid-grown R. centenum, which swims by using a single polar flagellum, to that of surface-grown R. centenum, which swarms over agar by using many lateral flagella and has been shown to move as colonies toward specific wavelengths of light. When suspended in liquid medium, both liquid-and surface-grown R. centenum showed similar responses to the light gradient. In all cases, free-swimming cells responded to the steep gradient of intensity but not to the shallow gradient, indicating they cannot sense the direction of light propagation but only its intensity. In a control experiment, the known phototactic alga Chlamydamonas reinhardtii was shown to swim in the direction of light propagation.

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Photomovement of Motile Microorganisms

Cited by 91 publications

References 185 publications

Motility of Electric Cable Bacteria

Motility of Electric Cable Bacteria

Photomovement in Euglena

Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

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