Striking convergent evolution is found in the properties of the organic osmotic solute (osmolyte) systems observed in bacteria, plants, and animals Polyhydric alcohols, free amino acids and their derivatives, and combinations of urea and methylamines are the three types of osmolyte systems found in all water-stressed organisms except the halobacteria The selective advantages of the organic osmolyte systems are, first, a compatibility with macromolecular structure and function at high or variable (or both) osmolyte concentrations, and, second, greatly reduced needs for modifying proteins to function in concentrated intracellular solutions Osmolyte compatibility is proposed to result from the absence of osmolyte interactions with substrates and cofactors, and the nonperturbing or favorable effects of osmolytes on macromolecular-solvent interactions

https://science.sciencemag.org/content/sci/217/4566/1214.full.pdf

Living with water stress: evolution of osmolyte systems

INTRODUCTION 89 BACKGROUND: THE BASIC PHYSIOLOGY 91 Conclusions 9S ION RELATIONS 96' Ion Uptake and Osmotic Adjustment 96 Nutrient Uptake: NalK Specificity 99 Ion Distribution within the Plant 100 Ion Distribution within the Cell 100 Metabolic evidence 100 Physical measurements .... .... ......... ...... 104 Energetics 106 ROLE OF ORGANIC SOLUTES ........ 108 OrganiC Acids 108 Nitrogen Compounds 109 Carbohydrotes 110 CONCLUSIONS 114

The mechanism of salt tolerance in halophytes

A fellow of my acquaintance, on seeing a colleague drink undiluted water (55.5 molal), has been known to comment in disapproval that water at such a concentration should not be used for that purpose and that its main function is for putting around the outside of boats. He conceded that dilution with a little salt is acceptable for boats but for no other purpose. The proponent of this philosophy is not a biologist and it is unlikely that many biologists would accept his generalization without some qualification. Nevertheless, it is a point of view. Another point of view with which all biologists might not agree, at least initially, is one which I wish to advance in this review. It is that, notwithstanding the indispensability of water in living systems and the unique properties of solvent water, quantitative variations in the amount of water available are of less direct microbiological significance than is generally conceded.

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1991&context=smhpapers

Microbial water stress.

Publisher Summary This chapter discusses the accumulation of amino acids and related compounds in relation to environmental stress. Amino acids and other soluble nitrogenous compounds play essential roles in plant metabolism, being the primary products of inorganic nitrogen assimilation and precursors of proteins and nucleic acids. The chapter describes the influence of some environmental stresses, both physical and biological, on the metabolism of soluble nitrogenous compounds. The soluble nitrogen fraction in plants is markedly affected by severe mineral element deficiency; both the concentration and composition of this fraction changes in response to deficiencies of particular mineral elements. All mineral deficiencies, with the exception of nitrogen and molybdenum, promote an increase in the soluble nitrogen fraction. Arginine, like the amides, often accumulates in response to deficiencies of most macro and many micro nutrients. The accumulation of amides and arginine in response to mineral deficiencies can reflect their role as nitrogenous storage compounds.

Accumulation of amino acids and related compounds in relation to environmental stress.

The recent progresses in the research on proline will be described, focusing on plants and covering proline metabolism and signal transduction as well as the role of this imino acid in stress response. Furthermore, the recently described developmental role of proline in flowering and reproduction will be illustrated and discussed.

Multiple roles of proline in plant stress tolerance and development

1. The total free amino acid concentration in Miamiensis avidus in 100% sea water is 317 mM/kg cells. Alanine, glycine and proline account for 73% of the total.2. Reducing the external osmolarity resulted in a decrease in intracellular free amino acids; raising the external osmolarity resulted in an increase in free amino acids. At the extreme salinities tested, cells in 25% sea water contained 24% of the free amino acids of cells in 100% sea water; cells in 200% sea water had a 22% greater free amino acid content than cells in 100% sea water. All of the changes were complete 20 minutes after the salinity changes.3. The intracellular free amino acid content was a function of external osmolarity, and not ionic strength or concentration of individual ions.4. The mechanism of the increase in free amino acid content was mobilization of bound amino acids, and not uptake from the medium.5. These results, together with earlier findings on regulation of ions and water in Miamiensis avidus, suggest that this organ...

Osmoregulation in a marine ciliate, miamiensis avidus. ii. regulation of intracelluar free amino acids

1. The K and Na content of Tetrahymena pyriformis has been determined, and the mechanisms of ionic regulation were investigated.2. The main findings were: K and a small amount of Na are maintained in very dilute medium. Cellular K and Na are readily exchangeable with K and Na of the medium. However, small, constant amounts of each are unexchangeable. Cells rapidly equilibrate with media high in K or Na. High K washes out of cells slowly, whereas Na enters and washes out of cells with equal facility. There is no reciprocal relationship between cellular K and Na. Tetrahymena contains little Cl. Increases in cellular K or Na are not accompanied by increases in Cl.3. The results are interpretable according to the following proposals: K is specifically accumulated and retained by a system of internal binding sites with a saturation level. Na is probably retained by a separate mechanism. There is also a Na extrusion mechanism which has no relationship with K or Na retention. Cellular K and Na are compartmentali...

Ion regulation in tetrahymena

@Little is known of the content and regulation of inorganic ions in marine proto zoa. The ionic composition of Uronema fihificum (Thompson and Kaneshiro, 1968) , a marine ciliate, has been determined (Kehlenbeck et al., 1965) and certain aspects of contractile vacuole function have been studied in several forms (Kitching, 1938,1967). Miamiensis avidus (Thompson and Moewus, 1964) , a euryhaline ciliate, can be studied after exposure to large changes in environmental osmolarity. Also, it grows axenically in mass cultures and has a short generation time, so chemical analyses are feasible. Taking advantage of these features, we have sought infor mation on the function of the contractile vacuole and on the kinds and concentra tions of internal inorganic ions. MATERIALS AND METHODS

Osmoregulation in a marine ciliate, miamiensis avidus. i. regulation of inorganic ions and water

1. A culture of Tetrahymena pyriformis adapted to a high NaCl medium, containing 220 mM NaCl, was investigated. The concentration of NaCl in the medium of the normal (unadapted) animals was about 35 mM.2. Upon direct transfer to the high NaCl medium, only 2% of the normal cells were sufficiently tolerant of the stress to survive and divide. Data were presented indicating that stress tolerance is a heritable character, and that this character was selected for upon transfer to the high NaCl medium.3. The cell volume of the adapted cells was 45% less than that of the normal animals. The adapted cells were more nearly spherical than normal cells. Despite the smaller size of the adapted cells, the amount of non-volatile material per cell was the same in normal and adapted cells.4. The main feature of the adaptation was a greatly increased ability of adapted cells to maintain a low cellular salt concentration. Sodium concentration in normal cells in normal medium was 13 meq./l. of cells. Sodium concentration in...

https://www.jstor.org/stable/pdfplus/1539307.pdf

THE ADAPTATION OF TETRAHYMENA TO A HIGH NaCl ENVIRONMENT

1. The concentrations of Na, K and Cl of pellets of sedimented sperm of Arbacia, Mytilus and Phascolosoma have been determined. With the aid of inulin space determinations on the pellets, it can be shown that sperm resemble other cells studied in maintaining, relative to the sea water environment, high internal K concentrations and low Na and Cl.2. Sperm of the three species were separated into head-midpieces and tail fractions. The former retain the ionic selection properties of the whole sperm. Isolated tails appear freely diffusible to all constituents including inulin.3. Using radioactive tracers it is shown that Na and K of sperm are freely exchangeable with the environment.

Philip B. Dunham

Papers

Osmoregulation in a marine ciliate, miamiensis avidus. ii. regulation of intracelluar free amino acids

Ion regulation in tetrahymena

Osmoregulation in a marine ciliate, miamiensis avidus. i. regulation of inorganic ions and water

THE ADAPTATION OF TETRAHYMENA TO A HIGH NaCl ENVIRONMENT

Ionic gradients in some invertebrate spermatozoa