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J. Bacteriol., Dec 1997, 7233-7242, Vol 179, No. 23
JL Wylie, GM Hatch and G McClarty
There is little information on the trafficking of eukaryotic lipids from a
host cell to either the cytoplasmic membrane of or the vacuolar membrane
surrounding intracellular pathogens. Purified Chlamydia trachomatis, an
obligate intracellular bacterial parasite, contains several eukaryotic
glycerophospholipids, yet attempts to demonstrate transfer of these lipids
to the chlamydial cell membrane have not been successful. In this report,
we demonstrate that eukaryotic glycerophospholipids are trafficked from the
host cell to C. trachomatis. Phospholipid trafficking was assessed by
monitoring the incorporation of radiolabelled isoleucine, a precursor of C.
trachomatis specific branched-chain fatty acids, into host-derived
glycerophospholipids and by monitoring the transfer of host
phosphatidylserine to chlamydiae and its subsequent decarboxylation to form
phosphatidylethanolamine. Phospholipid trafficking to chlamydiae was
unaffected by brefeldin A, an inhibitor of Golgi function. Furthermore, no
changes in trafficking were observed when C. trachomatis was grown in a
mutant cell line with a nonfunctional, nonspecific phospholipid transfer
protein. Host glycerophospholipids are modified by C. trachomatis, such
that a host-synthesized straight- chain fatty acid is replaced with a
chlamydia-synthesized branched- chain fatty acid. We also demonstrate that
despite the acquisition of host-derived phospholipids, C. trachomatis is
capable of de novo synthesis of phospholipids typically synthesized by
prokaryotic cells. Our results provide novel information on chlamydial
phospholipid metabolism and eukaryotic cell lipid trafficking, and they
increase our understanding of the evolutionary steps leading to the
establishment of an intimate metabolic association between an obligate
intracellular bacterial parasite and a eukaryotic host cell.
Copyright © 1997, American Society for Microbiology
Host cell phospholipids are trafficked to and then modified by Chlamydia trachomatis
Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
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