A1 Refereed original research article in a scientific journal

Content and biosynthesis of polyamines in salt and osmotically stressed cells of Synechocystis sp PCC 6803




AuthorsJantaro S, Maenpaa P, Mulo P, Incharoensakdi A

PublisherELSEVIER SCIENCE BV

Publication year2003

JournalFEMS Microbiology Letters

Journal name in sourceFEMS MICROBIOLOGY LETTERS

Journal acronymFEMS MICROBIOL LETT

Volume228

Issue1

First page 129

Last page135

Number of pages7

ISSN0378-1097

DOIhttps://doi.org/10.1016/S0378-1097(03)00747-X(external)


Abstract
The effects of various NaCl and sorbitol concentrations in the growth medium on polyamine content and on two enzymes of the polyamine biosynthesis pathway, arginine decarboxylase (ADC) and S-adenosyl methionine decarboxylase (SAMDC), were investigated in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Synechocystis cells showed no difference in growth rate when the concentration of NaCl was raised up to 550 mM. The growth rate decreased at 300 mM sorbitol, and complete inhibition of growth occurred at concentrations of greater than or equal to 700 mM sorbitol. Salt stress induced a moderate increase in the total cellular polyamine content, spermine in particular. Osmotic stress caused an apparent increase in the total cellular polyamine content with a marked increase of spermidine induced by 700 mM sorbitol. Importantly, a low level of spermine, which so far has never been detected in cyanobacteria, could be found in Synechocystis sp. PCC 6803. ADC, a key enzyme for putrescine synthesis, was unaffected by salt stress but showed a six-fold increase in enzyme activity upon osmotic stress imposed by 700 mM sorbitol. SAMDC, another important enzyme for spermidine and spermine synthesis, responded to salt and osmotic stresses similarly to the pattern observed for ADC. An analysis by reverse transcription-polymerase chain reaction revealed an increase of ADC mRNA level in cells under salt and osmotic stresses. Most importantly, the increase of ADC mRNA was attributed to its slower turnover rate under both stress conditions. Interestingly, the samdc gene(s) of Synechocystis appear to be unique since comparisons with known gene sequences from other organisms resulted in no homologous sequences identified in the Synechocystis genome. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Microbiological Societies.



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