Glycosylation of
Pseudomonas aeruginosa
Strain Pa5196 Type IV Pilins with Mycobacterium-Like α-1,5-Linked
d
-Ara
f
Oligosaccharides
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abstract
ABSTRACTPseudomonas aeruginosa
is a gram-negative bacterium that uses polar type IV pili for adherence to various materials and for rapid colonization of surfaces via twitching motility. Within the
P. aeruginosa
species, five distinct alleles encoding variants of the structural subunit PilA varying in amino acid sequence, length, and presence of posttranslational modifications have been identified. In this work, a combination of mass spectrometry and nuclear magnetic resonance spectroscopy was used to identify a novel glycan modification on the pilins of the group IV strain Pa5196. Group IV pilins continued to be modified in a lipopolysaccharide (
wbpM
) mutant of Pa5196, showing that, unlike group I strains, the pilins of group IV are not modified with the O-antigen unit of the background strain. Instead, the pilin glycan was determined to be an unusual homo-oligomer of α-1,5-linked
d
-arabinofuranose (
d
-Ara
f
). This sugar is uncommon in prokaryotes, occurring mainly in the cell wall arabinogalactan and lipoarabinomannan (LAM) polymers of mycobacteria, including
Mycobacterium tuberculosis
and
Mycobacterium leprae
. Antibodies raised against
M. tuberculosis
LAM specifically identified the glycosylated pilins from Pa5196, confirming that the glycan is antigenically, as well as chemically, identical to those of
Mycobacterium. P. aeruginosa
Pa5196, a rapidly growing strain of low virulence that expresses large amounts of glycosylated type IV pilins on its surface, represents a genetically tractable model system for elucidation of alternate pathways for biosynthesis of
d
-Ara
f
and its polymerization into mycobacterium-like α-1,5-linked oligosaccharides.
