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'Public Investment in Pfiesteria
Research Paying Off'
The Pfiesteria Files, a Maryland
Sea Grant video, captured top honors in the Wildlife Category of
the Outdoor Writers Association of America's annual competition.
The video was also nominated for an Emmy. |
NOAA
scientists recently reported that the singled-celled organism, Pfiesteria
piscicida, associated with fish kills and human health
problems in the mid-1990s in North Carolina and Maryland has a very
simple life cycle. This conclusion is based on results of a new federally
funded and peer-reviewed study published in the June 20 issue of the
Journal of Phycology, the leading US publication on marine and
freshwater algae.
"This research is a giant step forward in understanding how Pfiesteria
works. We now know our focus must extend well beyond Pfiesteria
alone," said principal author Dr. R. Wayne Litaker, of NOAA's Center
for Coastal Fisheries and Habitat Research and University of North Carolina's
Program in Molecular Biology and Biotechnology.
Researchers from NOAA, the University of North Carolina and North Carolina
State University used highly sophisticated molecular technology adapted
from medical research for closer study of Pfiesteria. With the
help of this new technology, NOAA researchers were able to show that
Pfiesteria has a simple life cycle like many similar marine dinoflagellates.
Past research has shown Pfiesteria to have a complex 24-stage
life cycle that included many toxic amoeboid stages. The new research
revealed no amoeboid stages in Pfiesteria's life cycle, bringing
into question the nature of the toxicity ascribed to this species.
Photo
by Dr. Pat Tester
"Our carefully controlled studies, including those where Pfiesteria
had been reared under conditions reported to produce amoebae, found
no evidence of an exotic life cycle involving multiple amoeboid stages,"
said study co-author Dr. Patricia A. Tester, of NOAA's Center for Coastal
Fisheries and Habitat Research, in Beaufort, N.C. "Rather, the life
cycle of Pfiesteria is similar to the life cycles of other marine
dinoflagellates."
"Even though we found that Pfiesteria does not have toxic amoeboid
stages, that does not mean Pfiesteria or other toxic harmful
algal bloom species should not be of concern to the health of America's
estuaries and coastal regions," said Wayne Litaker. "Our work is far
from done if we are to better understand the causes of fish kills and
associated human health concerns. Ongoing research will therefore seek
to zero-in on the potential causes of these problems."
The primary tool used in this study was a "fluorescently labeled peptide
nucleic acid (PNA) probe" recently developed for use in medical research.
The use of PNA probes in this study represents one of the first times
this technology has been used in marine research. The probe used in
this study was designed to bind specifically to a unique DNA sequence
only found in Pfiesteria piscicida.
To find that unique Pfiesteria DNA sequence, the researchers
sequenced a region of DNA from more than 100 cell isolates of Pfiesteria
and closely related species. These sequences were aligned using sophisticated
computer technologies so that a sequences only found in Pfiesteria
could be identified. A PNA probe that would only bind the unique Pfiesteria
sequence was then synthesized. The PNA was next mixed with Pfiesteria
cells taken from cultures where Pfiesteria was exposed to either
fish or other algae cells. The Pfiesteria-specific PNA entered
the cells in each sample, but only bound to the Pfiesteria life
cycle stages carrying the unique DNA sequence.
The results of the PNA probe studies also were confirmed by carefully
observing the life cycle using high-resolution microscopy. Other tests,
including amoeba-specific PNA probes, showed that any amoebae in the
Pfiesteria tanks were different species commonly found in estuaries
and not part of the Pfiesteria life cycle. These "normal" amoebae
species were contaminants introduced by the fish and were present in
the fish tank even before Pfiesteria cells were added. The study
underscores the need for further research to determine causes of fish
kills and public health problems previously reported to be associated
solely with Pfiesteria exposures.
"This public investment in Pfiesteria research is paying off.
PNA technology has opened a door to better understanding of toxic phytoplankton
and their risks to coastal resources and public health," said Pat Tester.
"The new scientific opportunities could help in detecting toxic algal
species and could improve monitoring and early warning systems designed
to protect those resources."
Joining her and Wayne Litaker in authoring the research are Mark W.
Vandersea and Steven R. Kibler, NOAA Center for Coastal Fisheries Habitat
Research program; Dr.Victoria J. Madden of the University of North Carolina's
Microscopy Services Laboratory, Pathology and Laboratory Medicine; and
Dr. Edward J. Noga, Department Of Clinical Sciences, North Carolina
State University College of Veterinary Medicine.
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