Phototaxis and other sensory phenomena in purple photosynthetic bacteria

Gest, Howard

doi:10.1111/j.1574-6976.1995.tb00176.x

Cited by 28 publications

(16 citation statements)

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“…In contrast to individual cell movement in liquid media, the purple phototrophic bacterium Rhodospirillum centenum exhibits phototaxis of colonies on soft (0.8%) agar, driven by a lateral flagellum (14). Such photoresponsive behavior in purple phototrophic bacteria was thought to be unique to R. centenum (8,16), although some species of cyanobacteria are capable of phototaxis (5, 7).…”

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“…Purple phototrophic bacteria in liquid media reverse the direction of flagellum-driven movement in response to a sudden change in light intensity. This "Schreckbewegung" or "scotophobic" response occurs regardless of the direction of the light source, which is not phototaxis (2,8,16). Experiments on Rhodobacter sphaeroides indicated that this response to a change in light intensity requires the light-dependent catalytic activity of the photosynthetic apparatus, but the signal transduction pathway that connects this primary sensation to flagellum rotation is not known (3).…”

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“…The movements of microbes in response to illumination have been studied for more than 100 years (6,8). Purple phototrophic bacteria in liquid media reverse the direction of flagellum-driven movement in response to a sudden change in light intensity.…”

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Photoresponsive Flagellum-Independent Motility of the Purple Phototrophic Bacterium Rhodobacter capsulatus

2005

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We report the discovery of photoresponsive, flagellum-independent motility of the ␣-proteobacterium Rhodobacter capsulatus, a nonsulfur purple phototrophic bacterium. This motility takes place in the 1.5% agar-glass interface of petri plates but not in soft agar, and cells move toward a light source. The appearances of motility assay plates inoculated with wild-type or flagellum-deficient mutants indicate differential contributions from flagellar and flagellum-independent mechanisms. Electron microscopy confirmed the absence of flagella in flagellar mutants and revealed the presence of pilus-like structures at one pole of wild-type and mutant cells. We suggest that R. capsulatus utilizes a flagellum-independent, photoresponsive mechanism that resembles twitching motility to move in a line away from the point of inoculation toward a light source.

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Photoresponsive Flagellum-Independent Motility of the Purple Phototrophic Bacterium Rhodobacter capsulatus

2005

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“…Many bacteria are motile and propel themselves by rotating helical flagella driven by molecular motors (51,113). Since the initial observations of bacterial motility, a rich set of "taxes" (i.e., directional movement responses) in response to external stimuli have been identified (70), including motion directed by light (phototaxis), temperature (thermotaxis), magnetic fields (magnetotaxis), electric fields (galvanotaxis), pH (pHtaxis), oxygen (aerotaxis), and chemical cues (chemotaxis) (29,59,63,91). The most ubiquitous and best studied of these behaviors is chemotaxis (112).…”

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Ecology and Physics of Bacterial Chemotaxis in the Ocean

Stocker

Seymour

2012

Microbiol Mol Biol Rev

257

214

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SUMMARYIntuitively, it may seem that from the perspective of an individual bacterium the ocean is a vast, dilute, and largely homogeneous environment. Microbial oceanographers have typically considered the ocean from this point of view. In reality, marine bacteria inhabit a chemical seascape that is highly heterogeneous down to the microscale, owing to ubiquitous nutrient patches, plumes, and gradients. Exudation and excretion of dissolved matter by larger organisms, lysis events, particles, animal surfaces, and fluxes from the sediment-water interface all contribute to create strong and pervasive heterogeneity, where chemotaxis may provide a significant fitness advantage to bacteria. The dynamic nature of the ocean imposes strong selective pressures on bacterial foraging strategies, and many marine bacteria indeed display adaptations that characterize their chemotactic motility as “high performance” compared to that of enteric model organisms. Fast swimming speeds, strongly directional responses, and effective turning and steering strategies ensure that marine bacteria can successfully use chemotaxis to very rapidly respond to chemical gradients in the ocean. These fast responses are advantageous in a broad range of ecological processes, including attaching to particles, exploiting particle plumes, retaining position close to phytoplankton cells, colonizing host animals, and hovering at a preferred height above the sediment-water interface. At larger scales, these responses can impact ocean biogeochemistry by increasing the rates of chemical transformation, influencing the flux of sinking material, and potentially altering the balance of biomass incorporation versus respiration. This review highlights the physical and ecological processes underpinning bacterial motility and chemotaxis in the ocean, describes the current state of knowledge of chemotaxis in marine bacteria, and summarizes our understanding of how these microscale dynamics scale up to affect ecosystem-scale processes in the sea.

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“…A more accurate description of this phenomenon is that when smooth-swimming cells migrate into a dark region (or into regions of the spectrum where wavelengths are not absorbed by photopigments), they either tumble or reverse the direction of movement, depending on the species. The phenomenon has been termed a scotophobic (fear of darkness) response since the cells exhibit an aversion to darkness rather than a specific affinity for light (12,29). Since a reduction in light intensity causes a tumbling/reversal response, the mechanism of moving through an increasing gradient of light intensity appears to involve a directed "random walk" such that the length of smooth swimming is longer when cells are going up a light gradient than when they are going down.…”

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Analysis of a chemotaxis operon from Rhodospirillum centenum

Jiang

Bauer

1997

J Bacteriol

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A chemotaxis gene cluster from the photosynthetic bacterium Rhodospirillum centenum has been cloned, sequenced, and analyzed for the control of transcription during swimmer-to-swarm cell differentiation. The first gene of the operon (cheAY) codes for a large 108-kDa polypeptide with an amino-terminal domain that is homologous to CheA and a carboxyl terminus that is homologous to CheY. cheAY is followed by cheW, an additional homolog of cheY, cheB, and cheR. Sequence analysis indicated that all of the che genes are tightly compacted with the same transcriptional polarity, suggesting that they are organized in an operon. Cotranscription of the che genes was confirmed by demonstrating through Western blot analysis that insertion of a polar spectinomycin resistance gene in cheAY results in loss of cheR expression. The promoter for the che operon was mapped by primer extension analysis as well as by the construction of promoter reporter plasmids that include several deletion intervals. This analysis indicated that the R. centenum che operon utilizes two promoters; one exhibits a 70 -like sequence motif, and the other exhibits a 54 -like motif. Expression of the che operon is shown to be relatively constant for swimmer cells which contain a single flagellum and for swarm cells that contain multiple lateral flagella.More than a century ago, Engelmann (7) observed that when purple sulfur photosynthetic bacteria of the genus Chromatium were illuminated with a broad spectrum of light, the cells accumulated at wavelengths that corresponded to the in vivo absorption peaks of the cells. A more accurate description of this phenomenon is that when smooth-swimming cells migrate into a dark region (or into regions of the spectrum where wavelengths are not absorbed by photopigments), they either tumble or reverse the direction of movement, depending on the species. The phenomenon has been termed a scotophobic (fear of darkness) response since the cells exhibit an aversion to darkness rather than a specific affinity for light (12,29). Since a reduction in light intensity causes a tumbling/reversal response, the mechanism of moving through an increasing gradient of light intensity appears to involve a directed "random walk" such that the length of smooth swimming is longer when cells are going up a light gradient than when they are going down. Superficially, this process is not unlike the wellcharacterized bacterial "trial-and-error" walking up a chemical gradient that is mediated by chemoreceptors and the Che protein phosphorylation cascade (2, 40).The mechanism whereby a reduction in light intensity causes a tumbling/reversal response is still unclear. However, recent work has revealed that a functioning photosynthetic apparatus is required for photosensory perception (3). In addition, chemical inhibition of electron carrier components such as the cytochrome bc 1 complex, are incapable of light perception (4). These results have led to the current dogma that the scotophobic response is mediated by the perception of a sudden decre...

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Phototaxis and other sensory phenomena in purple photosynthetic bacteria

Cited by 28 publications

References 21 publications

Photoresponsive Flagellum-Independent Motility of the Purple Phototrophic Bacterium Rhodobacter capsulatus

Photoresponsive Flagellum-Independent Motility of the Purple Phototrophic Bacterium Rhodobacter capsulatus

Ecology and Physics of Bacterial Chemotaxis in the Ocean

Analysis of a chemotaxis operon from Rhodospirillum centenum

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