Previous Article | Next Article ![]()
Applied and Environmental Microbiology, November 1999, p. 4822-4829, Vol. 65, No. 11
Fachbereich Biologie, Universität
Rostock, D-18051 Rostock, Germany
Received 20 May 1999/Accepted 11 August 1999
Synthesis of the osmolyte glucosylglycerol (GG) in the marine
cyanobacterium Synechococcus sp. strain PCC 7002 was
characterized. The ggpS gene, which encodes the key enzyme
(GG-phosphate synthase [GgpS]) in GG biosynthesis, was cloned by
using PCR. A 2,030-bp DNA sequence which contained one open reading
frame (ORF) was obtained. The protein deduced from this ORF exhibited
85% similarity to the GgpS of the freshwater cyanobacterium
Synechocystis sp. strain PCC 6803. The function of the
protein was confirmed by generating a ggpS null
mutant, which was not able to synthesize GG and thus exhibited a
salt-sensitive phenotype. Expression of the ggpS gene was
analyzed in salt-shocked cells by performing Northern blot and
immunoblot experiments. While almost no expression was detected in
cells grown in low-salt medium, immediately after a salt shock the
amounts of ggpS mRNA and GgpS protein increased up to
100-fold. The finding that salt-induced expression occurred was
confirmed by measuring enzyme activities, which were negligible in
control cells but clearly higher in salt-treated
Synechococcus sp. cells. The salt-induced increase in GgpS
activity could be inhibited by adding chloramphenicol, while in protein
extracts of the freshwater cyanobacterium Synechocystis sp.
strain PCC 6803 a constitutive, high level of enzyme activity that
was not affected by chloramphenicol was found. A comparison of GG
accumulation in the two cyanobacteria revealed that in the marine
strain osmolyte synthesis seemed to be regulated mainly by
transcriptional control, whereas in the freshwater strain control
seemed to be predominantly posttranslational.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Expression of the ggpS Gene, Involved in
Osmolyte Synthesis in the Marine Cyanobacterium
Synechococcus sp. Strain PCC 7002, Revealed Regulatory
Differences between This Strain and the Freshwater Strain
Synechocystis sp. Strain PCC 6803
*
Corresponding author. Mailing address: FB Biologie,
Universität Rostock, Doberaner Str. 143, D-18051 Rostock,
Germany. Phone: 49-381-4942076. Fax: 49-381-4942079. E-mail:
mh{at}bio4.uni-rostock.de.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»