EMBARGOED FOR RELEASE:
Thursday, 14 September 2000 at 14:00 U.S. Eastern Time
Researchers discover new
bacterial photopigment that
into biochemical energy
MOSS LANDING, California—Microscopic bacteria in the world's oceans have
only recently been detectable, but new studies are revealing surprising
evidence of their importance.
Microbiologists from the Monterey Bay Aquarium Research Institute (MBARI)
report in the 15 September 2000 issue of the journal Science their
discovery of a novel light-absorbing pigment found in oceanic bacteria.
The MBARI researchers describe how this new photopigment can generate
cellular energy using light. Their discovery suggests that a whole new
class of microorganisms is capable of harnessing light energy in the
ocean's sunlit surface zone.
"We've uniquely applied new advances in genomic technology to our
studies of oceanic microbes and it has lead us to unexpected
results," said lead researcher Ed DeLong. "We now have the
techniques to address some important ecological questions about the role
of these microorganisms in the ocean."
Microbiologists who study oceanic picoplankton—microscopic bacteria
that are 0.2 to 2 micrometers in diameter—face the challenge of studying
microorganisms that cannot be readily grown in culture. Using new
techniques, biologists have started to identify prominent groups of
microbes in the ocean, allowing them to map their distribution and
abundance. But the function of those microbes in their environment has
remained unknown. DeLong and postdoctoral associate Oded Béjà have
devised methods to dissect the genomes of the uncultivated microbes,
allowing them to identify the functions of specific genes, and predict
their ecological significance.
In this recent study, samples of oceanic bacteria were collected in
Monterey Bay. The MBARI researchers isolated large genome fragments and,
with colleagues at Amersham Pharmacia Biotech (Sunnyvale, CA), produced
the raw gene sequences from the picoplankton DNA. The sequences were
assembled and analyzed at MBARI to reveal the encoded genes and their
hypothetical function. The oceanic microbial genome sequence revealed a
new rhodopsin-like pigment never before found in any bacterial species. (Rhodopsins
are light-absorbing pigments, more familiarly associated with vision in
the animal kingdom.) The bacterial sequence suggested that this new
photopigment might serve as a type of light-driven ion pump, enabling the
oceanic microbes to generate energy from sunlight.
MBARI researchers used recombinant DNA technology to express and test
the function of the rhodopsin-like gene. As predicted, when exposed to
light, the photopigment moved ions across the cell membrane, showing that
it can generate energy by absorbing light. Additional bioinformatics
analysis and biophysical experiments necessary for this study were
conducted by researchers from the National Center for Biotechnology
Information (National Institutes of Health) and the University of Texas
DeLong and his colleagues are excited by the many implications of this
research, especially the demonstrated effectiveness of using genomics for
characterizing naturally-occurring microbes. Their research suggests that
rhodopsin-like photopigments appear to be more taxonomically widespread
than previously thought and reveals a new type of light-driven energy
generation in an abundant oceanic microbial group. For nanotechnology
development, this research has generated interest in the potential for new
applications in the area of light-actuated molecular switches.
Debbie Meyer, (831) 775-1807, firstname.lastname@example.org
Research article: Béjà, O., L. Aravind, E.V.
Koonin, M.T.Suzuki, A. Hadd, L.P. Nguyen, S.B. Jovanovich, C.M. Gates, R.A.
Feldman, J.L. Spudich, E.N.Spudich, and E.F. DeLong (2000). Bacterial
rhodopsin: Evidence for a new type of phototrophy in the sea. Science,
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