Use of Carbon Oxysulfide, a Structural Analog of CO2, to Study Active CO2 Transport in the Cyanobacterium Synechococcus UTEX 625

Miller, Anthony G.; Espie, George S.; Canvin, David T.

doi:10.1104/pp.90.3.1221

Cited by 51 publications

(46 citation statements)

References 20 publications

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“…1). In a recent study, we have confirmed that Chl a fluorescence quenching monitors inorganic carbon accumulation by direct measurements using the silicone fluid centrifugation technique (19 (Fig. 1).…”

Section: Fluorimetrymentioning

confidence: 51%

“…The use of COS, however, is complicated by the fact that it is broken down by CA or by intact cyanobacterial cells to CO2 and H2S (19). In this paper we demonstrate that H2S is also a potent, selective, and reversible inhibitor of active CO2 transport in the cyanobacterium Synechococcus UTEX 625.…”

mentioning

confidence: 76%

“…Third, we have found that the transport of COS, a metabolized structural analog of CO2, by the CO2 transport system is inhibited by H2S (19). Since no appreciable intracellular pool of COS is formed, and given that much of the COS within the cell is hydrolyzed, it would appear that the H2S acts by directly preventing the uptake of COS (19). The effects of COS (19) and H2S (Figs.…”

Section: Co2 Effluxmentioning

confidence: 99%

“…We have recently found that COS, an isoelectronic structural analog of C02, inhibits active CO2 transport in Synechococcus UTEX 625 and that it is also an alternate substrate for the transport system (19). The use of COS, however, is complicated by the fact that it is broken down by CA or by intact cyanobacterial cells to CO2 and H2S (19).…”

mentioning

confidence: 99%

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Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Espie¹,

Miller²,

Canvin³

1989

Plant Physiol.

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The active transport of CO2 in the cyanobacterium Synechococcus UTEX 625 was inhibited by H2S. Treatment of the cells with up to 150 micromolar H2S + HS-at pH 8.0 had little effect on Nat-dependent HC03-transport or photosynthetic O2 evolution, but CO2 transport was inhibited by more than 90%. CO2 transport was restored when H2S was removed by flushing with N2. At constant total H2S + HS-concentrations, inhibition of CO2 transport increased as the ratio of H2S to HS-increased, suggesting a direct role for H2S in the inhibitory process. Hydrogen sulfide does not appear to serve as a substrate for transport. In the presence of H2S and Na -dependent HC03-transport, the extracellular CO2 concentration rose considerably above its equilibrium level, but was maintained far below its equilibrium level in the absence of H2S. The inhibition of CO2 transport, therefore, revealed an ongoing leakage from the cells of CO2 which was derived from the intracellular dehydration of HC03-which itself had been recently transported into the cells. Normally, leaked CO2 is efficiently transported back into the cell by the CO2 transport system, thus maintaining the extracellular CO2 concentration near zero. It is suggested that CO2 transport not only serves as a primary means of inorganic carbon acquisition for photosynthesis but also serves as a means of recovering CO2 lost from the cell. A schematic model describing the relationship between the CO2 and HCO3-transport systems is presented. 8,13,20) and Anabaena variabilis ( 11) MATERIALS AND METHODS Organisms and GrowthThe unicellular cyanobacterium Synechococcus leopoliensis UTEX 625 (University of Texas Culture Collection, Austin, TX) was grown with air-bubbling (0.05% v/v CO2) in unbuffered Allen's medium at 30°C as described previously (6). Experimental ConditionsCells were washed three times by centrifugation (1 min at l0,OOOg, Beckman microfuge B) and resuspended (7-9 sg Chl * mL-') in 25 mm BTP/HC1 buffer of the appropriate pH.The buffer contained about 15 uM DIC and 5 Mm Na+ as contaminants. Washed cells (6 mL) were subsequently placed in a thermostated (30°C) glass reaction vessel (20 mm diameter) and briefly purged with a stream of N2 to reduce the [02] to less than 75 AM. The chamber was then closed to the atmosphere and the cells were allowed to temperature equilibrate for several minutes in darkness. The reaction vessel contained a port for the inlet capillary of a mass spectrometer and the cell suspension was continuously stirred with a magnetic stirrer during measurements. Light was provided by a 387 www.plantphysiol.org on May 10, 2018 -Published by Downloaded from

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Section: Fluorimetrymentioning

confidence: 51%

mentioning

confidence: 76%

Section: Co2 Effluxmentioning

confidence: 99%

mentioning

confidence: 99%

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Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Espie¹,

Miller²,

Canvin³

1989

Plant Physiol.

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“…Likewise with air-adapted Scenedesmus, the Ko.5(DIC) at pH 5 to 6 required only 5 uM CO2, but 8 times higher CO2 was needed at this pH for the Ko.5(DIC) by C02-grown cells. In addition, the CO2 pump when present in unicellular algae is inhibited by COS (19,23) or H2S (5) and by salicylhydroxamic acid in Dunaliella (14). The other DIC-concentrating mechanism in Scenedesmus is considered to be an alkaline HCO3-transporter which functions between pH 7 to 11.…”

Section: Discussionmentioning

confidence: 99%

Two Systems for Concentrating CO₂ and Bicarbonate during Photosynthesis by Scenedesmus

Thielmann¹,

Tolbert²,

Goyal³

et al. 1990

Plant Physiol.

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Scenedesmus cells grown on high CO2, when adapted to air levels of CO2 for 4 to 6 hours in the light, formed two concentrating processes for dissolved inorganic carbon: one for utilizing CO2 from medium of pH 5 to 8 and one for bicarbonate accumulation from medium of pH 7 to 11. Similar results were obtained with assays by photosynthetic 02 evolution or by accumulation of dissolved inorganic carbon inside the cells. The CO2 pump with Ko.5 for 02 evolution of less than 5 micromolar CO2 was similar to that previously studied with other green algae such as Chlamydomonas and was accompanied by plasmalemma carbonic anhydrase formation. The HC03-concentrating process between pH 8 to 10 lowered the Ko.5 (DIC) from 7300 micromolar HC03-in high CO2 grown Scenedesmus to 10 micromolar in air-adapted cells.The HC03-pump was inhibited by vanadate (K, of 150 micromolar), as if it involved an ATPase linked HC03-transporter. The CO2 pump was formed on low CO2 by high-CO2 grown cells in growth medium within 4 to 6 hours in the light. The alkaline HC03-pump was partially activated on low CO2 within 2 hours in the light or after 8 hours in the dark. Full activation of the HC03-pump at pH 9 had requirements similar to the activation of the CO2 pump. Air-grown or air-adapted cells at pH 7.2 or 9 accumulated in one minute 1 to 2 millimolar inorganic carbon in the light or 0.44 millimolar in the dark from 150 micromolar in the media, whereas C02-grown cells did not accumulate inorganic carbon. A general scheme for concentrating dissolved inorganic carbon by unicellular green algae utilizes a vanadate-sensitive transporter at the chloroplast envelope for the CO2 pump and in some algae an additional vanadate-sensitive plasmalemma HC03-transporter for a HC03-pump.

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2000

J. Geophys. Res.

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The uptake of atmospheric carbonyl sulfide (COS) by the lichen species Ramalina rnenziesii, representative for the open oak woodland in central California, was studied under laboratory conditions. By use of a dynamic cuvette system, the controlling parameters for the COS uptake were investigated under climate chamber conditions. The thallus water content, essential for the overall physiology of lichens, was found to be of basic importance for the trace gas exchange. A water content of 30% was the approximate minimum for COS uptake, with increasing activity up to a water content of 200%. Additionally, actual atmospheric mixing ratios have a significant influence on the exchange. The COS uptake was found to be a linear function of the ambient COS mixing ratio resulting in a compensation point as low as 37 ppt. A temperature optimum of 25øC was indicative of a physiological basis of the COS uptake. The inhibition of the COS consumption in the presence of a specific inhibitor for the enzyme carbonic anhydrase proved this enzyme to be of key relevance for the uptake. All these variables controlling the COS deposition were integrated into an uptake algorithm to model the exchange behavior of this lichen. The applicability of the model to field data is demonstrated. Uptake rates on a dry weight basis normalized to optimized conditions (25øC; 450 ppt COS) reached 0.17 + 0.09 pmol g-• s-• (i.e. 4.2 _+ 2.2 pmol m-2 s-• thallus surface area, respectively). The contribution of lichens to the global COS sink strength is assigned to be about 0.3 Tg a-•, representing not a major but a significant sink. 1. Introduction Carbonyl sulfide (COS) is the most stable and abundant reduced sulfur gas in the atmosphere. Nearly inert in the troposphere, it is transported into the stratosphere where it can bc photodissociated as well as oxidized to form SO•_ [Chin and Davis, 1993]. Subsequently, it is converted to sulfate aerosol and becomes part of the stratospheric aerosol layer [Crutzen, 1976; Meixner, 1984; Hofmann, 1990; Engel and Schmidt, 1994], influencing the Earth's radiation budget [7•trco et al., 1980] as well as heterogeneous reactions involved in stratospheric ozone chemistry [Roche, 1994; Fahey el al., 1993; Solomon et al., 1993]. Though no temporal trend in the tropospheric concentration of COS was observed during the past decade [Bandy et al., 1992; Rinsland et al., 1992], the global COS budget presented in the literature was thought to be seriously imbalanced, with sources exceeding sinks by a factor of 2 [Chin and Davis, 1993; Johnson et al., 1993]. Recently, Andreae and Crutzen [1997] proposed a correction toward a more balanced budget by exchanging the soil net source into a sink, an assumption that is based on findings of Castro and Galloway [1991] and De Mello and Hines [1994] and supported very recently by investigations of the COS exchange between soils and the atmosphere under laboratory as well as field conditions [Kuhn et al., 1999; Kesselrneier et al., 1999; Simmons et al., 1999]. The understanding of soils as a ...

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Use of Carbon Oxysulfide, a Structural Analog of CO₂, to Study Active CO₂ Transport in the Cyanobacterium Synechococcus UTEX 625

Cited by 51 publications

References 20 publications

Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Two Systems for Concentrating CO₂ and Bicarbonate during Photosynthesis by Scenedesmus

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Use of Carbon Oxysulfide, a Structural Analog of CO2, to Study Active CO2 Transport in the Cyanobacterium Synechococcus UTEX 625

Cited by 51 publications

References 20 publications

Selective and Reversible Inhibition of Active CO2 Transport by Hydrogen Sulfide in a Cyanobacterium

Selective and Reversible Inhibition of Active CO2 Transport by Hydrogen Sulfide in a Cyanobacterium

Two Systems for Concentrating CO2 and Bicarbonate during Photosynthesis by Scenedesmus

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Use of Carbon Oxysulfide, a Structural Analog of CO₂, to Study Active CO₂ Transport in the Cyanobacterium Synechococcus UTEX 625

Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Selective and Reversible Inhibition of Active CO₂ Transport by Hydrogen Sulfide in a Cyanobacterium

Two Systems for Concentrating CO₂ and Bicarbonate during Photosynthesis by Scenedesmus