Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Methods, Strains of Pfiesteria Are Both Critical in Determining Organism’s Toxicity

15.02.2005


Flagellated sexual cell of one of the two known toxic Pfiesteria species, Pfiesteria shumwayae, that were included in the study. Photo by M. Parrow, Center for Applied Aquatic Ecology.


To gauge the toxicity of Pfiesteria, the important single-celled fish predator that was the culprit behind a number of fish kills and fish diseases along the East Coast in the 1990s, researchers need to both use the proper study methods and recognize that certain populations of the organism, called strains, are toxic while others are not.

That’s the main result of a wide-ranging study by Dr. JoAnn M. Burkholder, professor and director of the Center for Applied Aquatic Ecology at North Carolina State University, along with a dozen colleagues from several universities and research institutions, and a federal laboratory specializing in marine toxins. The research is published online in Proceedings of the National Academy of Sciences.

The study reaffirmed that some strains of the two known Pfiesteria species are toxic, including a strain used by other researchers who had asserted that Pfiesteria can’t make toxin. Burkholder and her colleagues found that toxic Pfiesteria strains can produce toxin in the absence of bacteria or other contaminating microbes, and that small amounts of Pfiesteria can kill fish with toxin. They also showed that toxin from Pfiesteria can cause fish disease and death without Pfiesteria cells having to be present: water that at one time contained Pfiesteria, but was then completely filtered to remove all of the toxic Pfiesteria cells, caused lesions in fish.



Other experiments showed that purified Pfiesteria toxin residue added to cultures of larval fish killed the fish, while control fish without exposure to the toxin remained healthy.

In the study, two basic methods of detecting Pfiesteria toxicity were compared: fish microassays (FMAs) using larval fish, and standardized fish bioassays (SFBs) using juvenile fish. In each method, the scientists tested toxic Pfiesteria strains, known to be toxic from toxin detection tests that were completed by the National Oceanic and Atmospheric Administration’s National Ocean Service in Charleston, S.C. The researchers compared the results from the known toxic strains to tests of a strain of Pfiesteria previously reported as nontoxic, and with controls that included both Pfiesteria strains which did not express toxicity and a related nontoxic, single-celled organism similar to Pfiesteria.

FMAs were used to test larval fish in small containers with and without direct exposure to Pfiesteria. These tests examined whether direct contact with Pfiesteria was needed to cause death, and whether fish could become sick or die without direct contact with Pfiesteria.

FMAs had been proposed by other scientists as useful tests for ruling out the presence of toxic Pfiesteria – if fish don’t die when exposed to water filtered from a Pfiesteria culture, they asserted, then toxic Pfiesteria doesn’t exist. But lack of fish death does not necessarily mean Pfiesteria’s toxin isn’t there. “Unless the water was tested to see if Pfiesteria toxin was present, all that can be said from such a study is that there wasn’t enough toxin present to cause the fish to die,” explained Dr. Andrew Gordon, second author of the paper and a scientist at Old Dominion University. “More sensitive tests for the chemical toxin itself would be needed to say for sure whether toxin was or wasn’t present.”

Burkholder offered this analogy: “If a person drinks a glass of water from a well that sometimes contains arsenic, and the person doesn’t suddenly become very sick or die, would it be correct to say that the water didn’t contain any arsenic? Surely not – such a test wouldn’t be sensitive enough to detect levels of arsenic that were too low to cause sudden illness or death, but still were present, and still harmful. A test to detect arsenic would be needed.”

SFBs were better able to reliably detect actively toxic Pfiesteria than FMAs, Burkholder says, since SFBs were not developed to distinguish between toxicity and physical attack as factors in fish death, but instead designed to detect toxic Pfiesteria strains, which are known to routinely prey upon fish. “SFBs detected actively toxic strains. Those strains were verified as toxic by also actually testing for chemical toxin that they produced,” said Dr. Alan J. Lewitus, a scientist at the University of South Carolina, Georgetown and a co-author of the paper. “Toxin detection tests like the procedures developed by the National Ocean Service should be done along with fish assays to determine whether a toxic strain is present.”

The researchers also wanted to test whether Pfiesteria can produce toxin without help from bacteria and – as is known for other toxic algae – whether bacteria enhance Pfiesteria’s toxicity. Burkholder and her colleagues found that some strains of Pfiesteria were able to make toxin on their own, without bacteria. “However, when bacteria were present, Pfiesteria made more toxin,” noted Dr. Harold Marshall, a scientist at Old Dominion University and a co-author of the paper, “and a lot more toxin was produced when the toxic strains were given live fish.”

The study showed that conclusions about whether a species of algae is toxic should be based on tests of many strains, rather than one or a few, using culture conditions that encourage toxin production. “It’s also important to keep in mind that Pfiesteria changes when it’s cultured, after years of separation from its natural habitat,” Burkholder added. “Many toxic strains of Pfiesteria, like other toxic algae, even lose their ability to keep making toxin, so young cultures should be used as much as possible. This study clearly shows that Pfiesteria has benign strains and toxic strains, just like other toxic algae – it is the norm, not the exception. Research designed in recognition of that fact will make real progress in advancing scientific understanding about Pfiesteria.”

Dr. JoAnn M. Burkholder | EurekAlert!
Further information:
http://www.ncsu.edu

More articles from Life Sciences:

nachricht TU Bergakademie Freiberg researches virus inhibitors from the sea
27.03.2020 | Technische Universität Bergakademie Freiberg

nachricht The Venus flytrap effect: new study shows progress in immune proteins research
27.03.2020 | Jacobs University Bremen gGmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Junior scientists at the University of Rostock invent a funnel for light

Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.

The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.

Im Focus: Stem Cells and Nerves Interact in Tissue Regeneration and Cancer Progression

Researchers at the University of Zurich show that different stem cell populations are innervated in distinct ways. Innervation may therefore be crucial for proper tissue regeneration. They also demonstrate that cancer stem cells likewise establish contacts with nerves. Targeting tumour innervation could thus lead to new cancer therapies.

Stem cells can generate a variety of specific tissues and are increasingly used for clinical applications such as the replacement of bone or cartilage....

Im Focus: Artificial solid fog material creates pleasant laser light

An international research team led by Kiel University develops an extremely porous material made of "white graphene" for new laser light applications

With a porosity of 99.99 %, it consists practically only of air, making it one of the lightest materials in the world: Aerobornitride is the name of the...

Im Focus: Cross-technology communication in the Internet of Things significantly simplified

Researchers at Graz University of Technology have developed a framework by which wireless devices with different radio technologies will be able to communicate directly with each other.

Whether networked vehicles that warn of traffic jams in real time, household appliances that can be operated remotely, "wearables" that monitor physical...

Im Focus: Peppered with gold

Research team presents novel transmitter for terahertz waves

Terahertz waves are becoming ever more important in science and technology. They enable us to unravel the properties of future materials, test the quality of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“4th Hybrid Materials and Structures 2020” takes place over the internet

26.03.2020 | Event News

Most significant international Learning Analytics conference will take place – fully online

23.03.2020 | Event News

MOC2020: Fraunhofer IOF organises international micro-optics conference in Jena

03.03.2020 | Event News

 
Latest News

3D printer sensors could make breath tests for diabetes possible

27.03.2020 | Power and Electrical Engineering

TU Bergakademie Freiberg researches virus inhibitors from the sea

27.03.2020 | Life Sciences

The Venus flytrap effect: new study shows progress in immune proteins research

27.03.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>