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Infection and Immunity, April 2004, p. 2452-2455, Vol. 72, No. 4
0019-9567/04/$08.00+0 DOI: 10.1128/IAI.72.4.2452-2455.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
A Deep-Rough Mutant of Campylobacter jejuni 81-176 Is Noninvasive for Intestinal Epithelial Cells
Margaret I. Kanipes,1 Lindsay C. Holder,2 Adrian T. Corcoran,3 Anthony P. Moran,3 and Patricia Guerry2*
Department of Natural Sciences, Fayetteville State University, Fayetteville, North Carolina,1
Enteric Diseases Department, Naval Medical Research Center, Silver Spring, Maryland and,2
Department of Microbiology, National University of Ireland, Galway, Ireland3
Received 7 October 2003/
Returned for modification 17 November 2003/
Accepted 16 January 2004

ABSTRACT
A
waaF mutant of
Campylobacter jejuni 81-176 showed decreased
invasion of INT407 cells in vitro and increased sensitivity
to some antibiotics compared to what was seen with the wild-type
strain.

TEXT
The food-borne pathogen
Campylobacter jejuni is one of the principal
causes of human gastroenteritis worldwide (
7,
17). In addition,
C. jejuni is associated with the development of a devastating
neurological disorder, Guillain-Barré syndrome, perhaps
because of molecular mimicry between the outer core of
Campylobacter lipooligosaccharide (LOS) and the carbohydrate moiety of human
gangliosides (
15,
16).
C. jejuni strain 81-176 has been shown
in two human volunteer feeding studies to cause diarrhea (
5)
and has been studied extensively for molecular mechanisms of
pathogenesis (
2,
3,
5,
12-
14,
20).
C. jejuni 81-176 LOS (Fig.
1) is composed of two covalently linked domains: lipid A, a
hydrophobic anchor, and a nonrepeating core oligosaccharide
consisting of an inner and an outer core (
1,
10). The carbohydrate
structure of the outer core, consisting of hexoses and
N-acetylglucosamine,
primarily mimics GM
2 and GM
3 gangliosides, with minor amounts
of GD
2 and GD
1b mimics being detectable (
10). Two outer-core
mutants have been assayed for their ability to invade human
INT407 cells (
10). A mutant lacking
N-acetylneuraminic acid
invaded INT407 cells at the same levels as did the wild-type
strain, and interestingly, a mutant lacking the terminal GalNAc
showed a modest, but statistically significant, increase in
ability to invade INT407 cells (
10).
The inner-core region of
C. jejuni 81-176 LOS is structurally
similar to the same region of lipopolysaccharide (LPS) in enteric
bacteria such as
Escherichia coli and
Salmonella enterica serovar
Typhimurium (
11) (Fig.
1). It consists of a single 3-deoxy-
D-manno-2-octulosonic
acid residue (Kdo) attached to lipid A and two
L-glycero-
D-manno-heptose
(heptose) residues attached to the Kdo residue. The inner-core
region also contains a glucose residue and phosphoethanolamine
moiety attached to the first heptose residue. To better understand
the relationship between biosynthesis of the LOS and pathogenesis,
we initiated a study of the inner-core oligosaccharide of LOS
from
Campylobacter strain 81-176. The
waaF gene was identified
in an ordered partial Sau3A-digested genomic library of 81-176
DNA cloned into

-ZAPII (L. C. Holder and P. Guerry, unpublished
data). Four open reading frames (ORFs), organized in a fashion
similar to what is seen in other
C. jejuni strains (
8), were
revealed from the sequence analysis of plasmid pLCH3-4 (Fig.
2). ORF2 encoded a protein of 318 amino acids with a predicted
molecular mass of 36 kDa that showed significant similarity
to several WaaF enzymes that catalyze the transfer of the second
heptose to the core oligosaccharide of LPS and LOS. This ORF
product was 88% identical to the recently reported WaaF protein
from
C. jejuni 11828 (
19). In addition, sodium dodecyl sulfate
(SDS)-polyacrylamide gel electrophoresis followed by silver
staining showed that the 81-176
waaF gene is able to restore
LPS assembly by complementation of a
Salmonella serovar Typhimurium
waaF511 mutant strain, SL3789 (
22) (data not shown).
A
waaF::Cm insertional mutant was generated as previously described
(
9). One insertion that occurred 146 bp from the translational
start of
waaF was selected to electroporate 81-176 to Cm
r, and
a double crossover was confirmed by PCR (data not shown). The
LOS from the
waaF::Cm mutant migrated more quickly than that
of the wild-type strain (Fig.
3, lane 2 versus 1). The presence
of an LOS similar to that of the wild type was restored when
the
waaF mutant strain was complemented in
trans with pLCH1
(Fig.
2), which contains the 81-176
waaF gene (Fig.
3, lane
3). Table
1 lists the strains and plasmids used in this study.
A previous study has shown that the permethylated core oligosaccharide
of the parental strain 81-176 possesses pseudomolecular ions
with
m/z values of 1,943, 2,188, 2,548, and 2,752 [M + H]
+ corresponding
to cores exhibiting mimicry of GM
3, GM
2, GD
2, and GD
1b gangliosides,
respectively (
10). In contrast, the mass spectrum of the truncated
LOS species in the
waaF mutant possessed a pseudomolecular ion
with an
m/z value of 926 [M + H]
+ and related daughter ions
that may be interpreted as those of an LOS species that contains
glucose, heptose, phosphoethanolamine, and Kdo (Fig.
4). This
result supports the loss of the second heptose residue from
the LOS. Furthermore, glycosylation of a complete LOS requires
the transfer of the sugar catalyzed by the heptosyltransferase
II, WaaF.
Since there was no difference between the wild-type and
waaF mutant strains in growth or motility (data not shown), the ability
of the
C. jejuni 81-176 deep-rough mutant to invade INT407 human
intestinal epithelial cells was examined as previously described
(
2,
3,
18,
25). The data shown in Fig.
5 are expressed as the
percentage of the input inoculum internalized during the 2-h
gentamicin kill assay. The level of wild-type 81-176 invasion
(1.238% ± 0.634%) was 14-fold higher than that of the
waaF mutant (0.08% ± 0.074%). When the
waaF mutant was
complemented in
trans with pLCH1, the level of invasion was
restored to wild-type levels (2.0% ± 1.41%).
Deep-rough mutants of enteric bacteria are hypersensitive to
hydrophobic antibiotics and detergents due to major alterations
in the outer membrane (
11,
21). As shown in Table
2, the
C. jejuni waaF mutant showed hypersensitivity to the antibiotics
fusidic acid and novobiocin and the detergent SDS compared to
what was seen with the wild type. However, neither the wild-type
nor the
waaF mutant strain was sensitive to bacitracin, and
there was no difference in the sensitivities to gentamicin,
which was used in the invasion assays. Wild-type levels of resistance
to fusidic acid, novobiocin, and SDS were restored when the
waaF mutant was complemented in
trans.
Although a
waaF mutant (
19) of another
C. jejuni strain with
a core structure distinct from that of 81-176 (
10) has been
described, this is the first report of both the structure of
a
waaF core and complementation in
trans and the first report
to examine the effect of deep-rough mutations on virulence.
waaF mutants of a number of gram-negative bacteria have been
studied (
4,
6,
22), and
Haemophilus ducreyi and
Neisseria gonorrhoeae waaF mutants have been shown to be less virulent (
4,
23). This
reduction in invasion by the
C. jejuni waaF mutant may reflect
the need for a complete LOS for proper membrane function. As
with other deep-rough mutants, mutation of
waaF led to hypersensitivity
to various antibiotics. We are in the process of determining
whether loss of WaaF activity may result in additional changes
in the composition or structure of the outer membrane.
Nucleotide sequence accession number.
The nucleotide sequence of the region of the chromosome of C. jejuni 81-176 presented in Fig. 2 has been deposited in GenBank under accession number AY423899.

ACKNOWLEDGMENTS
This work was supported by the Military Infectious Diseases
Research Program and the Irish Health Research Board (A.P.M.).
M.I.K. was a recipient of an ASEE-NAVY summer faculty internship.
Special thanks to Gary Majam, Anahita Kiavand, Isabelle Walker, and other Guerry laboratory members for technical assistance.

FOOTNOTES
* Corresponding author. Mailing address: NMRC, Enteric Diseases Department, Naval Medical Center, 503 Robert Grant Ave., Silver Spring, MD 20910. Phone: (301) 319-7662. Fax: (301) 319-7679. E-mail:
guerryp{at}nmrc.navy.mil.

Editor: J. T. Barbieri

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Infection and Immunity, April 2004, p. 2452-2455, Vol. 72, No. 4
0019-9567/04/$08.00+0 DOI: 10.1128/IAI.72.4.2452-2455.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
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