The
spiral
and
curved
bacteria
Some
are
free
living
in
fresh
water
or
marine
environments.
others
are
saprophytic
or
parasitic
while
a
few
are
pathogenic
(Campylobaeter
fetus).The
most
important
genus
is
Spirillum.
Some
members
of
Spirillum
associate
with
roots
of
plants
and
fix
nitrogen.
Free
living
N2
fixation
occurs
under
microaerophilic
conditions.
Among
the
genera
of
uncertain
affiliation'
in
this
group
and
one
which
is
becoming
increasingly
important
is
the
genus
Bdellovibrio.
These
bacteria
are
single,
small
curved
motile
rods,
some
members
have
the
ability
of
to
attack,
penetrate
and
develop
within
various
Gram
positive
and
Gram
negative
bacteria.
Strains
of
Bdellovibrio
have
been
defined
on
the
basis
of
host
susceptibility
and
location
from
which
the
parasite
was
isolated.
Motility
is
by
means
of
a
single
polar
sheathed
flagellum
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