Lysosomes and sulfide-oxidizing bodies in the bacteriocytes of Lucina
pectinata, a cytochemical and microanalysis approach |
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Authors: | M Liberge O Gros L Frenkiel |
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Institution: | Université des Antilles et de la Guyane, Département de Biologie, 97159 Pointe-à-Pitre Cedex, Guadeloupe, France?e-mail: martine.liberge@univ-ag.fr, FR
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Abstract: | Lucina
pectinata is a large tropical clam living deeply burrowed in the black, reducing mud of mangrove swamps. It is known to possess hemoglobin
in the cytoplasmic areas of its bacteriocytes, which harbor sulfide-oxidizing bacteria. The bacteriocytes also possess lysosome-like
microbodies containing either membrane whorls or electron-dense granules in which free heme compounds have been identified.
The cytochemical detection of acid phosphatase and arylsulphatase through EDX (energy-dispersive X-ray) microanalysis strongly
suggests that the bacteriocytes of L.
pectinata contain, in fact, two different types of microbodies. Some of these (devoid of dense granules) possess a variable amount
of lysosomal enzymes and occasionally a limited quantity of iron, which may result from a recycling process of hemoglobin.
Their main function seems to be the digestion of a limited proportion of symbiotic bacteria. They represent genuine secondary
lysosomes with a functionally acidic pH. The second type of microbodies is characterized by dense granules containing sulfur
and iron hemes but no lysosomal enzymes. Their sulfide-oxidizing activity was substantiated by benzyl viologen assay, with
Na2S as a substrate. These microbodies appear to be similar to the sulfide-oxidizing bodies (SOBs) described in the bacteriocytes
of other bivalve species with symbiotic thioautotrophic bacteria; however, their sulfide-oxidizing activity appears to be
non-enzymatic. They are discrete organelles, characterized by a functionally basic pH and pseudoperoxidasic activity, and
have been termed SOBs. Therefore, the bacteriocytes of L.
pectinata possess at the same time functional lysosomes and functional SOBs.
Received: 17 August 2000 / Accepted: 20 December 2000 |
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