2024-03-28T22:44:08Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/83852016-02-16T03:51:26Zcom_10261_79com_10261_1col_10261_836
DIGITAL.CSIC
advisor
Marín Palma, Irma
author
Palacios Jurado, Lucía
2008-11-10T14:58:39Z
2008-11-10T14:58:39Z
2007
http://hdl.handle.net/10261/8385
Paralytic shellfish posisoning (PSP) is a life-threatening affection that results
from comsumption of seafood contaminated with paralytic shellfish toxins (PSTs),
which are potent neurotoxins comprising of saxitoxin (STX) and more than tweenty
other chemically related derivatives. PSTs blocks sodium channels, an action which
in humans leads to several neurological affections and in some cases death. So
far, PSTs have been detected in laboratory cultures of dinoflagellates mainly
belonging to the genera Alexandrium, Pyrodinium and Gymnodinium.
However, controversy surrounds suggestions that bacteria associated with these
dinoflagellates are either directly or indirecly involved in PST’s producction in
dinoflagellates. Bacterial influence on dinoflagellates toxicity was first postulated in
1960’s due to the ocurrence of bacteria-like particles within dinoflagellates cells.
Since then there have been several publications for and against these theories.
The present work aimed to examine the role of bacteria in dinoflagellates
toxicity, by defining their bacterial microbiology using microbiological clasical
techniques for bacterial isolation and molecular techniques such as DNA extraction,
16S rRNA clonning, DGGE or TSA-FISH, as well as confocal laser scanning
microscopy (CLSM).
In this study information is provided on Alexandrium minutum clones in
laboratory cultures from different origins. They were used to compare bacterial
profiles with the aim to correlate their toxicity differences with their bacterial
composition profiles.
During this study some methods were either developed or modified for use
specifically to study bacterial-toxic dinoflagellates interactions. A new bacteria
specie isolated from the toxic dinoflagellate Alexandrium minutum was also
proposed.
The results of clonning, DGGE and TSA-FISH showed that the bacterial
phylogenetic diversity was limited to two bacteria Phyla, the Proteobacteria (mainly
belonging to α and γ classes) and Bacteriodetes (Sphingobacteria class, Cytophaga-
Favobacter-Bacteroidetes). Results display a species-specific association between
some bacteria and the dinoflagellates clones in culture.
Confocal microscopy using Bacteria, Arquea and class specific oligonucleotide
probes demonstrated internal bacteria in Alexandrium minutum cells as well as
bacteria attached to the theca.
PST production in bacteria-free dinoflagellates compared to axenic cultures led to
the conclusion that bacteria could somehow influence dinoflagellate cell growth, as
well as some bacteria could directly influence PST’s concentrations in Alexandrium
minutum cultures. The mechanisms by which bacteria have this influence are
unknown altohugh the production of co-factors, signalling molecules, nutrient
availability and bacterial transformation of toxins was suggested.
Several researchers have reported specific interactions between bacteria and
phytoplankton, which has led them to propose that bacteria may play a role in
controlling phytoplankton dynamics. This study provide infomation from a range of
potentially algal-lytic tested bacteria isolated from Alexandrium minutum cultures.
These algal-lytic bacteria could play an important role in regulating the onset and
development of harmful algal blooms.
spa
openAccess
Alexandrium minutum
Microbiología marina
Estudio de la biodiversidad microbiana asociada a cultivos de Alexandrium minutum y sus posibles efectos sobre el crecimiento y la toxicidad algal
tesis doctoral
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URL
https://digital.csic.es/bitstream/10261/8385/1/Lucia%20Palacios.pdf
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https://digital.csic.es/bitstream/10261/8385/4/Lucia%20Palacios.pdf.txt
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Lucia Palacios.pdf.txt