Anthrax (Bacillus anthracis), Molecular Biology of
315
Repetitive elements
Separate amplified fragments by size using gel electrophoresis
Amplify DNA using primers
complementary to repetitive sequences.
Fig. 4
Long-range repetitive element
polymorphism-PCR (LR REP-PCR). Certain
sequences occur many times within a bacterial
genome, and these are called repetitive
elements. The number and location of these
REPs will vary between bacterial species. One
can use primers complementary to the REPs to
amplify fragments of DNA that will vary in size
depending on the spacing of the REPs in the
genome. As with AFLP, these fragments can be
separated by size using gel electrophoresis and
the patterns of fragments can be compared
between samples.
PCR fragments of different size will be
ampliFed in different strains, depending
on the spacing of REPs in each. This
technique clearly distinguishes between
B. anthracis
and related
Bacillus
species.
Another method that is proving useful
for
the
identiFcation
of
B. anthracis
is
multiple-locus
variable-number
tandem
repeat analysis (MLVA). Variable-number
tandem
repeat
(VNTR)
loci
are
short,
repeated sequences of DNA that vary in
copy number, thereby creating a length
polymorphism that can be detected by PCR
ampliFcation of fragments in the region.
Because of their greater diversity, these
markers have more power to discriminate
between species of bacteria than other
molecular typing methods. Most of the
MLVA primers developed for
B. anthracis
do not amplify sequences from related
Bacillus
species, so this method appears
to be useful in distinguishing
B. anthracis
from closely related species.
3.1.1
Post-October 2001 Research
Research efforts aimed at understanding
and detecting anthrax have been ramped
up since the intentional release of anthrax
in 2001. This research has covered ev-
erything from epidemiologic surveillance,
to methods of sample collection during
an investigation, and to rapid methods
for the detection of anthrax during a po-
tential outbreak. The following section
provides a discussion of the technologies
that were found to be useful in the detec-
tion of anthrax.
The sequence of the 16S rRNA gene is
often used to identify unknown bacteria.
Owing
to the
similarities between the
16S rRNA sequences of
B. anthracis
and
its
relatives,
it
was
thought
that
this
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