TY - JOUR
T1 - In situ identification and localization of bacteria associated with Gyrodinium instriatum (Gymnodiniales, Dinophyceae) by electron and confocal microscopy
AU - Alverca, Elsa
AU - Biegala, Isabelle C.
AU - Kennaway, Gabrielle M.
AU - Lewis, Jane
AU - Franca, Susana
PY - 2002/11
Y1 - 2002/11
N2 - The presence of intracellular bacteria in the dinoflagellate Gyrodinium instriatum Freudenthal & Lee has previously been described but the bacterial flora associated with this species has not been characterized. In this study, new results of transmission electron microscopy (TEM) and in situ hybridization using several bacterial group-specific oligonucleotide probes are presented. The long-term association of endocytoplasmic and endonuclear bacteria with G. instriatum has been confirmed. All endonuclear and most of the endocytoplasmic bacteria labelled were identified as belonging to the betaproteobacteria. Large clusters of Cytophaga-Flavobacterium-Bacteroides (CFB) were labelled and observed in the cytoplasm of the dinoflagellate cells, but were absent from the nucleus. Gammaproteobacteria were only observed outside the dinoflagellates. No alphaproteobacteria were detected either free-living or intracellular. Empirical observation of intracellular CFB reflected a degradation process of moribund dinoflagellate cells, whereas the systematic colonization of dinoflagellate nucleoplasm by betaproteobacteria suggested a true symbiotic relationship. Natural colonization may have occurred, perpetuated by vertical transmission of intracellular bacteria to the dinoflagellate daughter cells, via a pool of bacteria sequestered within the nucleus. Dividing bacteria were observed in the nucleus and equilibrium may be maintained by release of endonuclear bacteria to the cytoplasm through nuclear envelope constrictions.
AB - The presence of intracellular bacteria in the dinoflagellate Gyrodinium instriatum Freudenthal & Lee has previously been described but the bacterial flora associated with this species has not been characterized. In this study, new results of transmission electron microscopy (TEM) and in situ hybridization using several bacterial group-specific oligonucleotide probes are presented. The long-term association of endocytoplasmic and endonuclear bacteria with G. instriatum has been confirmed. All endonuclear and most of the endocytoplasmic bacteria labelled were identified as belonging to the betaproteobacteria. Large clusters of Cytophaga-Flavobacterium-Bacteroides (CFB) were labelled and observed in the cytoplasm of the dinoflagellate cells, but were absent from the nucleus. Gammaproteobacteria were only observed outside the dinoflagellates. No alphaproteobacteria were detected either free-living or intracellular. Empirical observation of intracellular CFB reflected a degradation process of moribund dinoflagellate cells, whereas the systematic colonization of dinoflagellate nucleoplasm by betaproteobacteria suggested a true symbiotic relationship. Natural colonization may have occurred, perpetuated by vertical transmission of intracellular bacteria to the dinoflagellate daughter cells, via a pool of bacteria sequestered within the nucleus. Dividing bacteria were observed in the nucleus and equilibrium may be maintained by release of endonuclear bacteria to the cytoplasm through nuclear envelope constrictions.
KW - Confocal microscopy
KW - Dinoflagellates
KW - Gyrodinium instriatum
KW - In situ hybridization
KW - Intracellular bacteria
KW - Oligonucleotide probes
KW - TEM
KW - Ultrastructure
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U2 - 10.1017/S0967026202003955
DO - 10.1017/S0967026202003955
M3 - Article
AN - SCOPUS:0036867132
SN - 0967-0262
VL - 37
SP - 523
EP - 530
JO - European Journal of Phycology
JF - European Journal of Phycology
IS - 4
ER -