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FROM THE LABS 109
laser into a type of microscope that
combines multiple microscopy tech-
niques and achieves a resolution of
about 100 nanometers.
WHY IT MATTERS: In addition to
imaging by means of light, the micro-
scope could eventually probe cells by
applying finely controlled amounts
of force with the nanowire; it could
then monitor how these forces change
the shape of cells and how the cells
respond to such mechanical stimuli.
This could give researchers a better
understanding of how cells work.
METHODS: Tiny forces exerted by
light from an infrared laser hold the
nanowire in place. The laser also ser ves
as an optical pump, providing a source
of energy that induces the nanowire
to emit green light. Images can be
obtained by measuring the light that
either passes through or re ects o a
sample as the nanowire moves over it.
The device can also be used to trace the
shape of a cell membrane by monitor-
ing the displacement of the nanowire
as it moves across the membrane.
NEXT STEPS: The researchers will
modify the shape of the nanowire
so that the laser can better hold it in
place: the wire tends to slide around in
the optical trap. A conical shape could
give the device better resolution and
give the researchers increased control
over mechanical probing.
Scientists successfully transform one
bacterial species into another
S OU RCE: "Genome Transplantation in
Bacteria: Changing One Species to
John I. Glass et al.
Science online, June 28, 2007
RESULTS: Scientists at the J. Craig
Venter Institute in Rockville, MD,
have transferred the entire genome
of one bacterium into another bacte-
rium. The host bacterium took on
characteristics of the donor---for
example, producing proteins speci c
to that species.
WHY IT MATTERS: Venter and his
colleagues aim to build genomes from
scratch and transplant them into bac-
terial cells in order to create custom-
made microörganisms, including ones
that produce fuel. Successful genome
transplant techniques will be necessary
to complete this process.
METHODS: The scientists isolated
the DNA of one species of mycoplasma,
a type of bacterium with a very small
genome, and gave it an additional gene
to make it resistant to an antibiotic.
The DNA was then transplanted into
a related mycoplasma species. As the
host bacteria grew and divided in the
presence of the antibiotic, cells carry-
ing only the species original chromo-
somes died, leaving just the cells with
the transplanted chromosome.
NEXT STEPS: Venter Institute
researchers will next try to determine
whether or not genome transplantation
is possible in other species of bacteria.
They are also developing a synthetic
version of the genome of a di erent
species of mycoplasma, which they
will attempt to transplant as well.
Genes for Several
A study of seven illnesses, including
diabetes and cardiovascular disease,
identifies possible culprits
SOURCE: "Genome-Wide Association
Study of 14,000 Cases of Seven Common
Diseases and 3,000 Shared Controls"
The Wellcome Trust Case Control
Nature 447: 661--678
RESULTS: A massive genetic study
carried out in the United Kingdom
pinpointed 24 genetic markers that
increase risk for seven common ill-
nesses. The study found one marker
for bipolar disorder, one for coronary-
artery disease, nine for Crohn s dis-
ease, three for rheumatoid arthritis,
seven for type 1 diabetes, and three
for type 2 diabetes.
WHY IT MATTERS: Unlike rare dis-
eases such as Huntington s, where a
single genetic variation guarantees that
a carrier will be a icted, common dis-
eases are triggered by a complex array
of factors, including multiple genes each
exerting a modest e ect. The new study
illustrates the success of a new approach
to gene hunting known as genome-
wide association, in which scientists
scour the entire genome for disease-
speci c variations. The vast scope of
such studies---in this case, almost 10 bil-
lion pieces of DNA---provides enough
statistical power for researchers to nd
genetic variations that raise the risk of
disease by a modest amount.
METHODS: The scientists used gene
chips to analyze 500,000 genetic mark-
ers in each of 17,000 people. To identify
genetic variations linked to speci c dis-
eases, they compared the DNA of 2,000
patients who had one of the diseases
with that of 3,000 healthy controls.
NEXT STEPS: The researchers will
try to con rm additional genetic varia-
tions hinted at in the current study by
analyzing genomic information from
larger numbers of people.
COURTESY OF THE J. CRAIG VENTER INSTITUTE
Colonies of successfully transformed
bacteria are shown here in blue.
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