Nelson, D. C.. University of California, dcnelson@ucdavis.edu
McHatton, S. C.. University of California, scmchatton@ucdavis.edu
Ahmad, A. A.. University of California, aaahmad@ucdavis.edu
Barry, J. P.. Monterey Bay Aquarium Research Institute, barry@mbari.org

 
MATS OF VACUOLATE FILAMENTOUS SULFUR BACTERIA: ADAPTATION TO ANOXIA AT VENTS AND SEEPS?
 
Sulfide-oxidizing bacterial mats, composed of extremely wide filaments belonging to the genus Beggiatoa or Thiothrix, are dominant features on sediments, rocks, or worm tubes at certain sulfidic deep sea hydrothermal vents and shallower seeps. Typically these filaments are several centimeters long, and all strains greater than 15 micrometers in diameter contain a large central vacuole. Whenever examined, the filaments have been found to contain nitrate, presumably in the vacuole, at concentrations greater than 150 mM. A respiratory conversion of nitrate to ammonia driven by oxidation of hydrogen sulfide or endogenous stores of elemental sulfur is indicated. Theoretically their chemoautotrophic growth can be sustained by internal stores of oxidant and reductant for several hours to days. These bacteria proliferate in regions low in dissolved oxygen but high in sulfide and combined nitrogen. Their dominance is speculated to be enhanced by relief from predation afforded by transient periods of anoxia. Small subunit ribosomal RNA sequence data obtained for a representative Beggiatoa sp. indicate very close evolutionary affinity with Thioploca spp. from Chilean oxygen minimum zone sediments. Because Thioploca is also vacuolate and nitrate -accumulating, this suite of adaptations appears to be monophyletic.
 
Day: Tuesday, Feb. 2
Time: 10:30 - 10:45am
Location: Sweeney Center
 
Code: SS27TU1030S