The Contribution of Photosynthate to Turgor Pressure Rise in the Planktonic Blue-green Alga<i>Anabaena flos-aquae</i>

Grant, Neil G.; Walsby, A. E.

doi:10.1093/jxb/28.2.409

Cited by 45 publications

(23 citation statements)

References 2 publications

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“…Of the two mechanisms, the Anabaenatype described here would appear to provide a more rapid loss of buoyancy at high light intensity since a substantial rise in turgor pressure can occur within only 30 min (Grant and Walsby 1977;Allison and Walsby 198 1). This might be the preferred mechanism in cyanobacteria that perform diel vertical migrations in lakes where there is a vertical separation between light and available nutrients (Fogg and Walsby 197 1;Ganf 1974;Ganf and Oliver 1982).…”

Section: Discussionmentioning

confidence: 88%

“…tent of the filaments as indicated by lightscattering measurements (Dinsdale and Walsby 1972). Collapse of gas vesicles was caused by a rise in cell turgor pressure (Walsby 197 1;Dinsdale and Walsby 1972) generated partly by the accumulation of organic products of photosynthesis (Grant and Walsby 1977) and partly by uptake of potassium ions (Allison and Walsby 198 1). The results of these previous experiments strongly suggest that the loss of buoyancy is caused by the collapse of gas vesicles brought about by rising turgor pressure, but they do not provide rigorous proof of this.…”

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confidence: 99%

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Direct evidence for the role of light‐mediated gas vesicle collapse in the buoyancy regulation of Anabaena flos‐aquae (cyanobacteria)1

Oliver

Walsby

1984

Limnology & Oceanography

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134

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Quantitative measurements were made of the changes in gas vacuole volume and the major components of cell mass (protein and carbohydrate) on cultures of Anabaenaflos-aquae which lost buoyancy as they were shifted from low to high light intensity. Assuming densities of 1,300 kg. rn-' for protein and 1,600 for carbohydrate, we calculated the change in ballast brought about by changes in these components and compared them with ballast changes resulting from gas vacuole collapse. We also compared the calculated excess density of filaments with direct measurements of filament density in gradients of Percoll. The results clearly demonstrated that increased density resulted from the loss of gas vacuoles. Small variations in density could be attributed to changes in protein and carbohydrate but these would not have caused a loss of buoyancy in the absence of a decrease in gas vacuole content. Analyses of the type described can be used to determine the cause of buoyancy change in other microorganisms and can be performed onOphytoplankton collected from lakes.

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Section: Discussionmentioning

confidence: 88%

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confidence: 99%

Direct evidence for the role of light‐mediated gas vesicle collapse in the buoyancy regulation of Anabaena flos‐aquae (cyanobacteria)1

Oliver

Walsby

1984

Limnology & Oceanography

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134

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“…Walsby's (1969) original observation that a laboratory strain of Anabaena flos-aquae became buoyant when maintained at low light intensity but lost buoyancy within an hour of transfer to high-light was shown subsequently to be due to the collapse of a pro-portion of the gas-vesicles in response cell turgor of 0.1 MPa (Dinsdale & Wi Oliver & Walsby 1984). The increased ti sure is generated partly by the photosyn duction of low molecular weight carl (Grant & Walsby 1977) and partly b dependent uptake of potassium ions . Photosynthetically reversals in the buoyancy of naturally Anabaena circinalis have been shown within 2-4 h when held in bottles suspe the lake surface (Reynolds 1975).…”

Section: The Turgor-collapse Mechanismmentioning

confidence: 99%

Cyanobacterial dominance: The role of buoyancy regulation in dynamic lake environments

Reynolds

Oliver

Walsby

1987

New Zealand Journal of Marine and Freshwater Research

396

208

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The interactions of size, shape, and density of cyanobacteria result in a 5-order of magnitude difference in flotation or sinking rates which, in turn, influence the extent of their dispersion in turbulent water masses. Active mixing through resource-replete waters of high clarity favours fastgrowing, small-celled species. Where photosynthetically active radiation is severely attenuated through the wind-mixed layer, species may rely on turbulent entrainment but must be adapted toward efficient light harvesting (morphological attenuation, enhanced pigmentation). In both strongly segregated waters (light-and nutrient-rich layers separated vertically) and waters experiencing highfrequency fluctuations in vertical mixing and optical depth, emphasis is placed on the ability to make rapid, buoyancy-adjusted vertical movements, favoured by large size. The cyanobacterial 1ife-forms respectively typical of these contrasted limnological systems -unicellular coccoids (e.g., Synechococcus), solitary filaments (e.g., Oscillatoria) and colonial forms (e.g., Microcystis) -illustrate the diversity of evolutionary adaptations to be discerned among the planktonic cyanobacteria and which contributes to their reputation as a prominent and successful group of organisms.

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“…If gas vesicle synthesis ceases, buoyancy may be lost as the cellular concentration of gas vesicles is diluted by cell growth and division (Walsby et al 1983). The thrid mechanism is irreversible collapse of gas vesicles under rising turgor pressure (Walsby 1971) generated through the photosynthetic production of low-molecularweight carbohydrates (Grant and Walsby 1977) and by lightdependent uptake of potassium ions (Allison and Walsby 1981). However, this mechanism probably is not responsible for buoyancy regulation in most natural populations (Walsby 1994).…”

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confidence: 99%

The effect of variations in irradiance on buoyancy regulation in Microcystis aeruginosa

Wallace

Hamilton

1999

Limnology & Oceanography

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A mechanism of buoyancy regulation in cyanobacteria was investigated in a fluctuating light environment typical of the mixed layer in a lake. New measurements of density and cellular carbohydrate content were obtained from a field sample of the cyanobacterium Microcystis aeruginosa. The rate of increase in carbohydrate and density in this cyanobacterium does not instantaneously adjust to an increase in light intensity. There is a time lag, the response time, corresponding to physiological adjustment to the increase in light, before equilibration of the rate of carbohydrate and density increase. Also, the rate of density and carbohydrate increase is nonlinear over the response time. Based on these experimental findings, a new model for buoyancy regulation was developed that includes the response time. This model was applied to two fluctuating light regimes that simulate Langmuir circulation and turbulence. The simulations reveal that the response time is critical in determining if a cell equilibrates its rate of density change to a change in the light that it receives. If the response time is longer than the time scale of the light fluctuation, then the rate of density increase will be less than the optimal equilibrium rate. Models that do not include the response time will not correctly predict the buoyancy of cyanobacteria and their water column position after an episode of mixing.

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The Contribution of Photosynthate to Turgor Pressure Rise in the Planktonic Blue-green AlgaAnabaena flos-aquae

Cited by 45 publications

References 2 publications

Direct evidence for the role of light‐mediated gas vesicle collapse in the buoyancy regulation of Anabaena flos‐aquae (cyanobacteria)1

Direct evidence for the role of light‐mediated gas vesicle collapse in the buoyancy regulation of Anabaena flos‐aquae (cyanobacteria)1

Cyanobacterial dominance: The role of buoyancy regulation in dynamic lake environments

The effect of variations in irradiance on buoyancy regulation in Microcystis aeruginosa

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