The obligate predatory Bdellovibrio bacteriovorus possesses a neutral lipid A containing alpha-D-Mannoses that replace phosphate residues: similarities and differences between the lipid As and the lipopolysaccharides of the wild type strain B. bacteriovorus HD100 and its host-independent derivative HI100.
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 beta-(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 alpha-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.
Department of Chemistry, Humboldt Universität zu Berlin, D-12489 Berlin, Germany.
Dominik
D
Schwudke
Michael
M
Linscheid
Eckhard
E
Strauch
Bernd
B
Appel
Ulrich
U
Zahringer
Hermann
H
Moll
Mareike
M
Muller
Lothar
L
Brecker
Sabine
S
Gronow
Buko
B
Lindner
D000911:Antibodies, Monoclonal; D001501:Bdellovibrio / Q000378:metabolism / Q000502:physiology*; D002240:Carbohydrate Sequence; D002241:Carbohydrates; D003460:Crystallization; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D007477:Ions; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008050:Lipid A / Q000737:chemistry*; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010710:Phosphates / Q000737:chemistry; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000911:Antibodies, Monoclonal; D002241:Carbohydrates; D005227:Fatty Acids; D007477:Ions; D008050:Lipid A; D008055:Lipids; D008070:Lipopolysaccharides; D010710:Phosphates; D011522:Protons; D014409:Tumor Necrosis Factor-alpha; D008358:Mannose