Type
IV
pili
(Tfp)
are
widespread
virulence
factors
whose
multifunctional
ability
sets
them
apart
from
other
pili.
Tfp
mediate
adhesion
as
well
as
aggregation,
competence
for
DNA
transformation
and
twitching
motility
(a
non-­flagellar
form
of
locomotion)
in
many
bacterial
pathogens.
The
molecular
mechanisms
of
these
functions
and
the
biogenesis
of
these
pili
are
not
yet
fully
understood.
To
better
understand
Tfp
biology,
our
group
started
a
systematic
characterization
of
all
of
the
proteins
involved
in
Tfp
biology
in
a
well-­defined
genetic
background,
Neisseria
meningitidis
strain
8013.
Screening
of
a
large
library
of
mutants
in
this
strain
followed
by
an
in-­depth
mining
of
the
genome
resulted
in
the
discovery
of
23
genes
that
may
be
involved
in
Tfp
biology.
Seven
of
these
genes
encode
proteins
deemed
“accessory”
for
Tfp
biogenesis
as
the
corresponding
mutants
are
piliated.
Since
previous
analysis
of
one
these
genes
(pilX)
led
to
the
finding
that
it
modulates
one
Tfp-­linked
function
(aggregation),
the
first
aim
of
my
project
was
to
phenotypically
characterize
mutants
in
the
remaining
genes
along
with
double
mutants
in
which
filament
retraction
is
abolished
by
a
concurrent
mutation
in
the
pilT
gene,
and
strains
overexpressing
the
corresponding
proteins
with
regards
to
levels
of
piliation,
adhesion,
aggregation
and
DNA
competence.
This
was
achieved
using
a
battery
of
quantitative
and
qualitative
methods
well-­established
in
our
research
group.
Results
from
this
study
showed
that
each
of
the
seven
proteins
plays
a
role
in
fine-­tuning
of
Tfp-­linked
function(s).
This
completed
our
systematic
study
of
mutants
in
N.
meningitidis
Tfp
biology,
and
gave
us
a
complete
picture
of
the
roles
of
these
proteins
in
Tfp
function.
This
provides
us
with
a
platform
for
further
in-­depth
study
of
these
proteins.
In
parallel,
we
attempted
to
further
characterize
one
of
these
proteins,
PilZ,
by
determining
its
localization
and
protein
structure,
however,
we
have
been
unsuccessful
in
both
efforts
so
far.
Finally
we
attempted
to
improve
upon
the
current
pilus
purification
method
using
a
His-­tagged
version
of
the
major
pilus
subunit
PilE
to
purify
fibres
by
affinity
chromatography.
This
could
be
a
very
useful
tool
for
future
studies.