NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Physical chemistry and evolution of salt tolerance in halobacteriaThe cellular constituents of extremely halophilic bacteria not only tolerate high salt concentration, but in many cases require it for optical functioning. The characteristics affected by salt include enzyme activity, stability, allosteric regulation, conformation and subunit association. The salt effects are of two major kinds: electrostatic shielding of negative charges by cations at low salt concentration, and hydrophobic stabilization by salting-out type salts at high salt concentration. The composition of halobacterial proteins shows an excess of acidic amino acids and a deficiency of nonpolar amino acids, which accounts for these effects. Since the cohesive forces are weaker and the repulsing forces are stronger in these proteins, preventing aggregation in salt, these structures are no longer suited for functioning in the absence of high salt concentrations. Unlike these nonspecific effects, ribosomes in halobacteria show marked preference for potassium over sodium ions. To ensure the proper intracellular ionic composition, powerful ion transport systems have evolved in the halobacteria, resulting in the extrusion of sodium ions and their replacement by potassium. It is likely that such membrane transport system for ionic movements is a necessary requisite for salt tolerance.
Document ID
19800056213
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lanyi, J. K.
(NASA Ames Research Center Moffett Field, Calif., United States)
Date Acquired
August 10, 2013
Publication Date
June 1, 1980
Subject Category
Life Sciences (General)
Accession Number
80A40383
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available