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. © 2009 Society for Applied Microbiology and Blackwell Publishing Ltd.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Microbiology
Research Field:	Bacteriology
Objective Division:	Health
Objective Group:	Public Health (excl. Specific Population Health)
Objective Field:	Food Safety
UTAS Author:	Shabala, Lana (Associate Professor Lana Shabala)
UTAS Author:	McMeekin, TA (Professor Thomas McMeekin)
UTAS Author:	Shabala, SN (Professor Sergey Shabala)
ID Code:	57295
Year Published:	2009
Web of Science® Times Cited:	14
Deposited By:	Agricultural Science
Deposited On:	2009-07-02
Last Modified:	2010-04-24
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