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Relationship between Sodium Influx and Salt Tolerance of Nitrogen-Fixing Cyanobacteria

By Shree Kumar Apte, Bontha Rajasekhar Reddy and Joseph Thomas

Abstract

The relationship between sodium uptake and cyanobacterial salt (NaCl) tolerance has been examined in two filamentous, heterocystous, nitrogen-fixing species of Anabaena. During diazotrophic growth at neutral pH of the growth medium, Anabaena sp. strain L-31, a freshwater strain, showed threefold higher uptake of Na(+) than Anabaena torulosa, a brackish-water strain, and was considerably less salt tolerant (50% lethal dose of NaCl, 55 mM) than the latter (50% lethal dose of NaCl, 170 mM). Alkaline pH or excess K(+) (>25 mM) in the medium causes membrane depolarization and inhibits Na(+) influx in both cyanobacteria (S. K. Apte and J. Thomas, Eur. J. Biochem. 154:395-401, 1986). The presence of nitrate or ammonium in the medium caused inhibition of Na(+) influx accompanied by membrane depolarization. These experimental manipulations affecting Na(+) uptake demonstrated a good negative correlation between Na(+) influx and salt tolerance. All treatments which inhibited Na(+) influx (such as alkaline pH, K(+) above 25 mM, NO(3)(−), and NH(4)(+)), enhanced salt tolerance of not only the brackish-water but also the freshwater cyanobacterium. The results indicate that curtailment of Na(+) influx, whether inherent or effected by certain environmental factors (e.g., combined nitrogen, alkaline pH), is a major mechanism of salt tolerance in cyanobacteria

Topics: General Microbial Ecology
Year: 1987
OAI identifier: oai:pubmedcentral.nih.gov:204028
Provided by: PubMed Central
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