X-Message-Number: 14785
Date: Thu, 26 Oct 2000 12:01:04 -0700 (PDT)
From: Doug Skrecky <>
Subject: PEG 200, 8000 have different effects on membranes

Title
  Differential effects of permeating and nonpermeating solutes
  on the fatty acid composition of Pseudomonas putida.
Source
  Applied & Environmental Microbiology.  66(6):2414-21, 2000 Jun.
Abstract
  We examined the effect of reduced water availability on the fatty acid
  composition of Pseudomonas putida strain mt-2 grown in a defined medium in
  which the water potential was lowered with the permeating
  solutes NaCl or polyethylene glycol (PEG) with a molecular
  weight of 200 (PEG 200) or the nonpermeating solute PEG 8000. Transmission
  electron microscopy showed that -1.0-MPa PEG 8000-treated cells had
  convoluted outer membranes, whereas -1.0-MPa NaCl-treated or
  control cells did not. At the range of water potential (-0.25 to -1.5 MPa)
  that we examined, reduced water availability imposed by PEG 8000, but not by
  NaCl or PEG 200, significantly altered the amounts of trans and cis isomers
  of monounsaturated fatty acids that were present in whole-cell fatty acid
  extracts. Cells grown in basal medium or under the -0.25-MPa water potential
  imposed by NaCl or PEG 200 had a higher trans:cis ratio than -0.25-MPa PEG
  8000-treated cells. As the water potential was lowered further with PEG 8000
  amendments, there was an increase in the amount of trans isomers, resulting
  in a higher trans:cis ratio. Similar results were observed in cells grown
  physically separated from PEG 8000, indicating that these changes were not
  due to PEG toxicity. When cells grown in -1.5-MPa PEG 8000 amendments were
  exposed to a rapid water potential increase of 1.5 MPa or to a
  thermodynamically equivalent concentration of the permeating solute, NaCl,
  there was a decrease in the amount of trans fatty acids with a corresponding
  increase in the cis isomer. The decrease in the trans/cis ratio following
  hypoosomotic shock did not occur in the presence of the lipid synthesis
  inhibitor cerulenin or the growth inhibitors chloramphenicol and rifampicin,
  which indicates a constitutively operating enzyme system. These results
  indicate that thermodynamically equivalent concentrations of permeating and
  nonpermeating solutes have unique effects on
  membrane fatty acid composition.

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=14785