Salt Adaptation of the Cyanobacterium Synechococcus 6311 Growing in a Continuous Culture (Turbidostat)

Abstract

Physiological aspects of salt-adaptation in the cyanobacterium Synechococcus 6311 growing in a continuous culture (turbidostat) were studied. The process of salt-adaptation was completed within 3 days, as expressed by the specific growth rate of cells grown in the presence of 0.2 and 0.4 molar NaCl. An increase in photosynthetic activity during the adaptation period leads to the accumulation of soluble sugars, essential for osmoregulation in the salt-grown cells. Cells grown in the presence of 0.4 molar NaCI showed an initial inhibition in the rate of protein synthesis which was enhanced after the 1st day of salt stress. After adaptation, salt-grown cells showed an increase in phycobiliprotein synthesis and a higher phycobiliprotein to protein ratio. and illuminated with cool white fluorescent light, I = 20 mw/ cm-.Cell Parameters. Dry weight, Chl, protein, and phycobiliprotein content were determined as described previously (1) Cells were grown in a turbidostat as described in "Materials and Methods." NaCI was added after a constant specific growth rate was achieved.

Salinity-stress-induced proteins in two nitrogen-fixing Anabaena strains differentially tolerant to salt

“…Most of these mechanisms have been shown to be induced by salt or osmotic stress (4,5,7,14,17,20,(22)(23)(24)28). It is obvious that while some of these mechanisms would operate in the cell membrane others would have to be developed in the cytoplasm during osmotic stress.…”

“…Although the molecular basis of the mechanisms involved in cyanobacterial salt tolerance is not fully understood, some concepts have emerged in recent years. Prominent among these mechanisms are (i) curtailment of Na+ influx and prevention of intracellular Na+ accumulation, which reduce the need to pump out excess Na+ and conserve energy, resulting in greater salt tolerance (1,2) (this mechanism, which is inherent in salt-tolerant strains [2], was recently shown to be also induced by environmental factors which inhibit Na+ influx, for example, high pH [1] or the presence of combined nitrogen [B. R. Reddy, S. K. Apte, and J. Thomas, Plant Physiol., in press]); (ii) accumulation of internal osmoticum in the form of inorganic ions, such as K' (17,24,28), or organic solutes, such as glucopyranosylglycerol (7), sucrose (4), trehalose (23), or glycine betaine (22); and (iii) metabolic adjustments to tune the cellular activities to function at higher internal osmoticum (5,28). Obviously, all these mechanisms imply modification(s) of the synthesis and/or activity of cell proteins to facilitate * Corresponding author.…”

Enhancement of Cyanobacterial Salt Tolerance by Combined Nitrogen

“…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).…”

CO2 Fixation Rate and RuBisCO Content Increase in the Halotolerant Cyanobacterium, Aphanothece halophytica, Grown in High Salinities

“…In the dark, carbon transfer from starch to glycerol has also been reported to occur in Dunaliella cells (9). Furthermore certain photosynthetic algae have been reported to increase photosynthetic activity or extractable enzyme activity of RuBisCO under high salinities (4,8). Gimmler et al (8) Table II.…”