X-Message-Number: 17035
Date: Fri, 20 Jul 2001 09:12:50 -0700 (PDT)
From: Doug Skrecky <>
Subject: glucosylglycerol looks interesting as a potential additive

<1> of <2>
Title
  Uptake and use of the osmoprotective compounds trehalose,
  glucosylglycerol, and sucrose by the cyanobacterium
  Synechocystis sp. PCC6803.
Source
  Archives of Microbiology.  167(2-3):112-8, 1997 Feb-Mar.
Abstract
  Accumulation of exogenously supplied osmoprotective compounds was analyzed in
  the cyanobacterium Synechocystis sp. PCC6803, which synthesizes
  glucosylglycerol as the principal osmoprotective compound.
  Glucosylglycerol and trehalose were accumulated to high
  levels and protected cells of a mutant unable to synthesize
  glucosylglycerol against the deleterious effects of salt
  stress. In the wild-type, uptake of trehalose repressed the synthesis of
  glucosylglycerol and caused metabolic conversion of
  originally accumulated glucosylglycerol. Trehalose cannot be
  synthesized by Synechocystis and was not or only insignificantly metabolized.
  Sucrose, which can be synthesized in low quantities by Synechocystis, was
  also taken up, as indicated by its disappearance from the medium. Sucrose was
  not accumulated to high levels, probably due to a sucrose-degrading activity
  found in cells adapted to both low- and high-salt conditions. Despite its low
  intracellular concentration, sucrose showed a weak osmoprotective effect in
  salt-shocked cells of a mutant unable to synthesize
  glucosylglycerol.

<2>
Title
  Active transport of glucosylglycerol is involved in salt
  adaptation of the cyanobacterium Synechocystis sp. strain PCC 6803.
Source
  Microbiology.  142 ( Pt 7):1725-32, 1996 Jul.
Abstract
  An active-transport system for the osmoprotective compound
  glucosylglycerol (GG) was found in the cyanobacterium
  Synechocystis sp. strain PCC 6803. Uptake assays with 14C-labelled GG showed
  that the GG transport was enhanced in cells adapted to increasing
  concentrations of NaCl. Kinetic studies indicated a Michaelis-Menten
  relationship. The uptake of GG was energy dependent and occurred against a
  steep concentration gradient. It was inhibited by uncouplers as well as by a
  combination of darkness and KCN. The affinity of the transporter seems to be
  restricted to osmoprotective compounds of cyanobacteria; from a variety of
  compounds tested only sucrose and trehalose competed with GG for uptake. A
  salt-sensitive mutant of Synechocystis 6803 unable to synthesize GG could be
  complemented to salt resistance by exogenous GG. Accumulation of GG from the
  medium was essential for the restoration of photosynthesis and growth in
  mutant cells under high-salt conditions. In wild-type cells, the GG
  transporter probably serves to prevent GG leaking out of salt-stressed cells.

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