Ion metabolism in a halophilic blue-green alga, Aphanothece halophytica

Miller, Donald M.; Jones, Jay H.; Yopp, John H.; Tindall, Donald R.; Schmid, Walther

doi:10.1007/bf00446561

Cited by 62 publications

(22 citation statements)

References 20 publications

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“…The photoautotrophic nitrogen-fixing cyanobacteria, in general, exhibit considerable tolerance to salt or osmotic stress (30) and reclamation of saline/sodic soils using these organisms has been attempted with some success (25). Adaptation to salt stress in cyanobacteria, although not adequately understood, consists of at least three phenomena: (a) accumulation of internal osmoticum in the form of inorganic ions (17) or organic solutes (6,15,20,22); (b) contribution of ion transport processes (1, 2, 4, 21, 23, 30); and (c) metabolic adjustments (7,30).…”

Section: Organisms and Growth Conditionsmentioning

confidence: 99%

Enhancement of Cyanobacterial Salt Tolerance by Combined Nitrogen

Reddy

Apte²,

Thomas³

1989

Plant Physiol.

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Presence of certain nitrogenous compounds in the growth medium significantly enhanced the salt tolerance of the freshwater cyanobacterium Anabaena sp. strain L-31 as well as the brackish water cyanobacterium Anabaena torulosa. Among these, nitrate, ammonium, and glutamine were most effective followed by glutamate and aspartate. These nitrogenous compounds also inhibited Na influx in both Anabaena spp. with the same order of effectiveness as that observed for protection against salt stress. The inhibition of Na+ influx on addition of the nitrogenous substances was rapid; nitrate and ammonium inhibited Na+ influx competitively. Proline and glycine did not affect Na+ influx and also had no influence on the salt tolerance of either Anabaena sp. The observed protection was not consequent to a stimulatory effect of combined nitrogen on growth per se. Uptake of N03-and NH4+ increased during salt stress but was not correlated with growth. Intracellular levels of N03-and NH4+ were found to be inadequate to constitute a major component of the intemal osmoticum. The results suggest that inhibition of Na+ influx by combined nitrogen is a major mechanism for protection of cyanobacteria against salt stress.

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Section: Organisms and Growth Conditionsmentioning

confidence: 99%

Enhancement of Cyanobacterial Salt Tolerance by Combined Nitrogen

Reddy

Apte²,

Thomas³

1989

Plant Physiol.

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“…Aphanothece halophytica is a halophilic cyanobacterium, unable to grow at or below 3.5% (w/v) NaCl (sea water salinity) (5). The osmotic adaptation of this organism was first studied by Miller et al (15) who showed that A. halophytica accumulated up to 1 M K+ in response to increasing external salinity. Recently, Reed et al (18) demonstrated that betaine is the major solute accumulated followed by K+ in four strains of cyanobacteria including A. halophytica grown in high salinity.…”

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confidence: 99%

Effect of Betaine on Enzyme Activity and Subunit Interaction of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase from Aphanothece halophytica

Incharoensakdi¹,

Takabe²,

Akazawa³

1986

Plant Physiol.

101

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The presence of betaine, a quaternary ammonium compound, at a concentration (0.5 molar) reported to accumulate inside Aphanothece halophytica in response to increasing external salinity, slightly promoted ribulose-1,5-bisphosphate (RuBP) carboxylase activity. KCI at 0.25 molar inhibited RuBP carboxylase about 55%. Betaine relieved the inhibition by 0.25 M KCI and the original uninhibited activity was restored at 1 M betaine. Other osmoregulatory solutes such as sucrose and glycerol also reduced KCI inhibition, though to a lesser extent than betaine. Proline had no effect. The protective effect of betaine against KCI inhibition of RuBP carboxylase activity was also observed in other cyanobacteria, i.e. Synechococcus ACMM 323, Plectonema boryanum, and Anabaena variabilis, and in the photosynthetic bacterium Rhodospirillum rubrum but not in Chromatium vinosum. Apart from betaine, other quaternary ammonium compounds, i.e. sarcosine and trimethylamine-N-oxide (TMAO), but not glycine, also protected the enzyme against KCI inhibition and the effectiveness of such compounds appeared to correlate with the extent of N-methylation. Heat and cold inactivation of the enzyme could be protected by either betaine or KCI. However, best protection occurred when both betaine and KCI were present together. The Km (CO2) was not altered by either betaine or KCI, nor when they were present together. However, the Km (RuBP) was increased about 5-fold by KCI, but was unaffected by betaine. The presence of betaine together with KCI lowered the KCI-raised Km (RuBP) by about half. The extent of the dissociation of the enzyme molecule under the condition of low ionic strength was reduced by either betaine or KCI alone and more so when they were present together. Glycine, sarcosine, and TMAO were more effective than betaine or KCI in lowering the extent of the dissociation of the enzyme molecule.

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“…Intracellular K + in Aphanothece halophytica was shown to be as high as 1 mol . dm-3, varying as a direct function of external salt concentration [47,48]. This suggests that halophilic cyanobacteria and non-halotolerant forms [49] may possess dissimilar K + transport mechanisms although more precise data for K f fluxes etc.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Transport of Potassium Ions in the Cyanobacterium Anabaena variabilis KutZ

1981

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Interrelationships between potassium-ion transport and transplasmalemma e.-ctrical-potential fference (A$,) have been investigated in Anabaena variahilis (ATCC 2941 3) by measuring K + translocation and membrane potential in parallel. At pH 7.0, 5 mmol . dm-3 external K f , there was a thirtyfold accumulation of K'. The K + equilibrium potential was lower (more negative) than the measured membrane potential by up to 20 mV, (A$K+ = -90 mV; A$,,, = -70 mV to -75 mV, respectively). Dark pretreatment and low temperature ( 4 T ) reduced internal K + and depolarized A$,,,. External pH affected K + translocation and membrane potential; A$,,, was hyperpolarized at high external p H ; transplasmalemma Kf fluxes and internal K + concentration were also increased at high pH. The effects of pH upon A$,,,, coupled with the finding that the membrane potential was relatively insensitive to external K + , suggest that A$, is unlikely to be due primarily to a diffusion potential of K', but that the membrane potential is maintained by an electrogenic proton-extrusion mechanism.There was no close (obligate) link between K + transport and changes in A$,,,. Carbonylcyanide m-chlorophenylhydrazone decreased K + fluxes, internal K + and A+,,, when added in amounts up to 100 pmol . dm-3, However, AI/IK+ was always more negative than A$,,,. Valinomycin up to concentrations of 50 pmol . d m -j increased transplasmalemma K + fluxes by up to 300%, while changes in A$, were negligible. Internal K + was unaffected by valinomycin. N,N'-Dicyclohexylcarbodiimide at concentrations up to 100 pmol . dm-3, reduced K t flux rates and caused a hyperpolarization of These observations suggest that A$,,, is primarily due to electron transport reactions at the plasmalemma and that K ' transport is energy-dependent.In the presence of dicyclohexylcarbodiimide, internal K + redistributed in accordance with the membrane potential, suggesting that passive uniport in response to A$,,, (i.e. secondary active transport) is not usually important but may operate when primary active mechanisms are blocked.

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Ion metabolism in a halophilic blue-green alga, Aphanothece halophytica

Cited by 62 publications

References 20 publications

Enhancement of Cyanobacterial Salt Tolerance by Combined Nitrogen

Enhancement of Cyanobacterial Salt Tolerance by Combined Nitrogen

Effect of Betaine on Enzyme Activity and Subunit Interaction of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase from Aphanothece halophytica

Characterization of the Transport of Potassium Ions in the Cyanobacterium Anabaena variabilis KutZ

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