title: Comparison of proton-specific ATPase activities in plume and root tissues of two co-occurring hydrocarbon seep tubeworm speciesLamellibrachia luymesiandSeepiophila jonesi.
abstract: Lamellibrachia luymesiandSeepiophila jonesiare co-occurring species of vestimentiferan tubeworms found at hydrocarbon seepage sites on the upper Louisiana slope of the Gulf of Mexico. Like all vestimentiferans, they rely on internal sulfide-oxidizing symbiotic bacteria for nutrition. These symbionts produce hydrogen ions as a byproduct of sulfide oxidation, which the host tubeworm needs to eliminate to prevent acidosis. The hydrothermal vent tubewormRiftia pachyptilauses a high activity of P- and V-type H+-ATPases located in its plume epithelium to excrete protons. UnlikeR. pachyptila, the seep species grow a posterior root, which they can use in addition to their plumes as a nutrient exchange surface. In this study we measured the ATPase activities of plume and root tissues collected fromL. luymesiandS. jonesi, and used a combination of inhibitors to determine the relative activities of P- and V-type H+-ATPases. We found that the total H+-ATPase activity of their plumes was approximately 14 μmol h-1g-1wet weight, and that of their roots was between 5 and 7 μmol h-1g-1wet weight. These activities were more than ten times lower than those measured inR. pachyptila. We suggest that seep tubeworms might use passive channels to eliminate protons across their roots, in addition to ATP-dependant proton pumps located in their plumes and roots. In addition, we found strong differences between the types of ATPase activities in the plumes ofL. luymesiandS. jonesi. While the H+-ATPase activity ofL. luymesiplumes is dominated by P-type ATPases,S. jonesihas an unusually high activity of V-type H+-ATPases. We suggest thatS. jonesirelies on its high V-type H+-ATPase activity to drive carbon dioxide uptake across its plume surface.L. luymesi, on the other hand, might rely partially on bicarbonate uptake across its root.
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802 USA ; Courant Research Centre Geobiology, Georg- August- Universität Göttingen, 370077 Göttingen, Germany.
authors.forename: Sharmishtha
authors.initials: S
authors.lastname: Dattagupta
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802 USA.
authors.forename: Meredith
authors.initials: M
authors.lastname: Redding
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802 USA.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Luley
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802 USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Fisher