This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Caro, A. Articles by Troussellier, M. Search for Related Content PubMed PubMed Citation Articles by Caro, A. Articles by Troussellier, M. Agricola Articles by Caro, A. Articles by Troussellier, M.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, April 2007, p. 2101-2109, Vol. 73, No. 7
0099-2240/07/$08.00+0     doi:10.1128/AEM.01683-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Characterization of the Population of the Sulfur-Oxidizing Symbiont of Codakia orbicularis (Bivalvia, Lucinidae) by Single-Cell Analyses ^,

Audrey Caro,^1,2* Olivier Gros,² Patrice Got,¹ Rutger De Wit,¹ and Marc Troussellier¹

UMR-CNRS 5119, Laboratoire Ecosystèmes Lagunaires, Université Montpellier II, 34095 Montpellier Cedex 5, France,¹ UMR-CNRS 7138, Systématique-Adaptation-Evolution, Equipe Symbiose, Université des Antilles et de la Guyane, UFR des Sciences Exactes et Naturelles, Département de Biologie, B.P. 592, 97159 Pointe-à-Pitre Cedex, Guadeloupe, France²

Received 19 July 2006/ Accepted 12 January 2007

We investigated the characteristics of the sulfur-oxidizing symbiont hosted in the gills of Codakia orbicularis, a bivalve living in shallow marine tropical environments. Special attention was paid to describing the heterogeneity of the population by using single-cell approaches including flow cytometry (FCM) and different microscopic techniques and by analyzing a cell size fractionation experiment. Up to seven different subpopulations were distinguished by FCM based on nucleic acid content and light side scattering of the cells. The cell size analysis of symbionts showed that the symbiotic population was very heterogeneous in size, i.e., ranging from 0.5 to 5 µm in length, with variable amounts of intracellular sulfur. The side-scatter signal analyzed by FCM, which is often taken as a proxy of cell size, was greatly influenced by the sulfur content of the symbionts. FCM revealed an important heterogeneity in the relative nucleic acid content among the subclasses. The larger cells contained exceptionally high levels of nucleic acids, suggesting that these cells contained multiple copies of their genome, i.e., ranging from one copy for the smaller cells to more than four copies for the larger cells. The proportion of respiring symbionts (5-cyano-2,3-ditolyl-terazolium chloride positive) in the bacteriocytes of Codakia revealed that around 80% of the symbionts hosted by Codakia maintain respiratory activity throughout the year. These data allowed us to gain insight into the functioning of the symbionts within the host and to propose some hypotheses on how the growth of the symbionts is controlled by the host.

---

* Corresponding author. Mailing address: UMR-CNRS 5119, Laboratoire Ecosystèmes Lagunaires, CC 93, Université Montpellier II, 34095 Montpellier Cedex 5, France. Phone: 33 4 67 14 41 85. Fax: 33 4 67 14 37 19. E-mail: audrey.caro{at}univ-montp2.fr.

Published ahead of print on 26 January 2007.

Supplemental material for this article may be found at http://aem.asm.org/.

---

Applied and Environmental Microbiology, April 2007, p. 2101-2109, Vol. 73, No. 7
0099-2240/07/$08.00+0     doi:10.1128/AEM.01683-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Caro, A., Got, P., Bouvy, M., Troussellier, M., Gros, O. (2009). Effects of Long-Term Starvation on a Host Bivalve (Codakia orbicularis, Lucinidae) and Its Symbiont Population. Appl. Environ. Microbiol. 75: 3304-3313 [Abstract] [Full Text]  
• Ball, A. D., Purdy, K. J., Glover, E. A., Taylor, J. D. (2009). Ctenidial structure and three bacterial symbiont morphotypes in Anodontia (Euanodontia) ovum (Reeve, 1850) from the Great Barrier Reef, Australia (Bivalvia: Lucinidae). J MOLLUS STUD 75: 175-185 [Abstract] [Full Text]