CO2 Uptake and Fixation by Endosymbiotic Chemoautotrophs from the Bivalve Solemya velum
View/ Open
1174.full.pdf (327.2Kb)
Access Status
Full text of the requested work is not available in DASH at this time ("restricted access"). For more information on restricted deposits, see our FAQ.Published Version
https://doi.org/10.1128/aem.01817-06Metadata
Show full item recordCitation
Scott, K. M., and C. M. Cavanaugh. 2006. “CO2 Uptake and Fixation by Endosymbiotic Chemoautotrophs from the Bivalve Solemya Velum.” Applied and Environmental Microbiology 73 (4) (December 8): 1174–1179. doi:10.1128/aem.01817-06.Abstract
Chemoautotrophic symbioses, in which endosymbiotic bacteria are the major source of organic carbon for the host, are found in marine habitats where sulfide and oxygen coexist. The purpose of this study was to determine the influence of pH, alternate sulfur sources, and electron acceptors on carbon fixation and to investigate which form(s) of inorganic carbon is taken up and fixed by the gamma-proteobacterial endosymbionts of the protobranch bivalve Solemya velum. Symbiont-enriched suspensions were generated by homogenization of S. velum gills, followed by velocity centrifugation to pellet the symbiont cells. Carbon fixation was measured by incubating the cells with 14C-labeled dissolved inorganic carbon. When oxygen was present, both sulfide and thiosulfate stimulated carbon fixation; however, elevated levels of either sulfide (>0.5 mM) or oxygen (1 mM) were inhibitory. In the absence of oxygen, nitrate did not enhance carbon fixation rates when sulfide was present. Symbionts fixed carbon most rapidly between pH 7.5 and 8.5. Under optimal pH, sulfide, and oxygen conditions, symbiont carbon fixation rates correlated with the concentrations of extracellular CO2 and not with HCO3− concentrations. The half-saturation constant for carbon fixation with respect to extracellular dissolved CO2 was 28 ± 3 μM, and the average maximal velocity was 50.8 ± 7.1 μmol min−1 g of protein−1. The reliance of S. velum symbionts on extracellular CO2 is consistent with their intracellular lifestyle, since HCO3− utilization would require protein-mediated transport across the bacteriocyte membrane, perisymbiont vacuole membrane, and symbiont outer and inner membranes. The use of CO2 may be a general trait shared with many symbioses with an intracellular chemoautotrophic partner.Other Sources
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1828671/Citable link to this page
http://nrs.harvard.edu/urn-3:HUL.InstRepos:14350395
Collections
- FAS Scholarly Articles [18292]
Contact administrator regarding this item (to report mistakes or request changes)