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Osmotic adjustment and requirement for sodium in marine protist thraustochytrid
Author(s) -
Shabala Lana,
McMeekin Tom,
Shabala Sergey
Publication year - 2009
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2009.01908.x
Subject(s) - biology , turgor pressure , sodium , osmotic shock , osmotic concentration , osmotic pressure , osmoregulation , mannitol , osmoprotectant , intracellular , flux (metallurgy) , biophysics , potassium , osmosis , biochemistry , microbiology and biotechnology , membrane , salinity , ecology , chemistry , amino acid , organic chemistry , proline , gene
Summary A non‐invasive ion‐selective microelectrode technique was used to elucidate the ionic mechanisms of osmotic adjustment in a marine protist thraustochytrid. Hypoosmotic stress caused significant efflux of Na + , Cl – and K + from thraustochytrid cells. Model calculations showed that almost complete osmotic adjustment was achieved within the first 30 min after stress onset. Of these, sodium was the major contributor (more than half of the total osmotic adjustment), with chloride being the second major contributor. The role of K + in the process of osmotic adjustment was relatively small. Changes in Ca 2+ and H + flux were attributed to intracellular signalling. Ion flux data were confirmed by growth experiments. Thraustochytrium cells showed normal growth patterns even when grown in a sodium‐free solution provided the medium osmolality was adjusted by mannitol to one of the seawater. That suggests that the requirement of sodium for thraustochytrid growth cycle is due to its role in cell osmotic adjustment rather than because of the direct Na + involvement in cell metabolism. Altogether, these data demonstrate the evidence for turgor regulation in thraustochytrids and suggest that these cells may be grown in the absence of sodium providing that cell turgor is adjusted by some other means.