The Obligate Predatory Bdellovibrio bacteriovorus Possesses a Neutral Lipid A Containing α-D-Mannoses That Replace Phosphate Residues

• Published in: The Journal of biological chemistry Vol. 278; no. 30; p. 27502
• Main Authors: Dominik Schwudke, Michael Linscheid, Eckhard Strauch, Bernd Appel, Ulrich Zähringer, Hermann Moll, Mareike Müller, Lothar Brecker, Sabine Gronow, Buko Lindner
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 25-07-2003
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M303012200

Bdellovibrio bacteriovorus are predatory bacteria that penetrate
Gram-negative bacteria and grow intraperiplasmically at the expense of the
prey. It was suggested that B. bacteriovorus partially degrade and
reutilize lipopolysaccharide (LPS) of the host, thus synthesizing an outer
membrane containing structural elements of the prey. According to this
hypothesis a host-independent mutant should possess a chemically different
LPS. Therefore, the lipopolysaccharides of B. bacteriovorus HD100 and
its host-independent derivative B. bacteriovorus HI100 were isolated
and characterized by SDS-polyacrylamide gel electrophoresis, immunoblotting,
and mass spectrometry. LPS of both strains were identified as smooth-form LPS
with different repeating units. The lipid As were isolated after mild acid
hydrolysis and their structures were determined by chemical analysis, by mass
spectrometric methods, and by NMR spectroscopy. Both lipid As were
characterized by an unusual chemical structure, consisting of a
β-(1→6)-linked 2,3-diamino-2,3-dideoxy- d -glucopyranose
disaccharide carrying six fatty acids that were all hydroxylated. Instead of
phosphate groups substituting position O-1 of the reducing and O-4′ of
the nonreducing end α- d -mannopyranose residues were found in
these lipid As. Thus, they represent the first lipid As completely missing
negatively charged groups. A reduced endotoxic activity as determined by
cytokine induction from human macrophages was shown for this novel structure.
Only minor differences with respect to fatty acids were detected between the
lipid As of the host-dependent wild type strain HD100 and for its
host-independent derivative HI100. From the results of the detailed analysis
it can be concluded that the wild type strain HD100 synthesizes an innate
LPS.