9630054 Taylor The microbial oxidation of geothermally produced sulfur compounds, principally hydrogen sulfide, is the energy base for supporting dense animal communities surrounding deep-sea hydrothermal vents. To broaden our understanding of this process in warm water vents laboratory enrichments were established where seawater in contact with coastal marine sediments were exposed to hydrogen sulfide in continuous flow reactors. A self sustaining white flocculant material became established that was found to be comprised of solid sulfur filaments that were 0.5-2.0 micrometers wide and ranged between 20-500 micrometers in length. Preliminary studies have shown that the filaments are produced via direct excretion by a motile bacterium and the filaments produced become a site for attachment and continued excretion by other members of the population. An intriguing observation in our laboratory indicates that filamentous sulfur may be an abundant product of free-living microbial sulfide oxidation in subseafloor regions of warm water hydrothermal vents. Recent descriptions of an extensive discharge from so-called called "blizzard" or "snowblower" vents on the East Pacific Rise indicated large amounts of white flocculant material was released and accumulated into mats of 5 cm thickness. We have examined this material and found it to be microscopically and chemically nearly identical to the filamentous sulfur material produced in our laboratory reactors. The overall goal of this project will be to study the microbial ecology of filamentous sulfur formation, and to apply this information to a greater understanding of the microbial processes occurring in warm water hydrothermal vents and other sulfidic open flow environments. We will focus on three interdependent areas of research: (A) Characterization of the process and physiology of the sul fide oxidizing organism directly responsible for filamentous sulfur formation, and study of the interactions between these organisms and the filamentous product that presumably allow their existence in high fluid flow environments. (B) Determine the taxonomic and phylogenetic characteristics of coastal filamentous sulfur-producing organisms. (C) Determination of the morphological mechanism of filamentous sulfur formation. The oxidation of hydrogen sulfide to elemental sulfur of filamentous form is a unique and undescribed phenomenon, and suggests a novel solution to a microbial existence in turbulent environments. Proposed studies, we believe, will provide the beginnings of an interesting new chapter in our understanding of the microbiology of the marine sulfur cycle, and will introduce a novel form of sulfur that may have future industrial application.
