UC San Diego

Submarine basaltic glass constitutes a major part of the oceanic crust and contains a number of bio-essential nutrients including Fe and Mn. Substantial biological activity can be inferred from bio-alteration textures that dominate basaltic glass alteration. However, the role of basaltic glass in fueling diverse chemolithotrophic communities within deep-sea ecosystems remains enigmatic. Little is known about the key mechanisms and potential ecological advantages that drive basaltic glass colonization, the extent to which microbial activity may affect alteration rates and the biogeochemical cycling of elements in particular along the basalt/water interface. The nutrient and energy availability in basalt is considered to facilitate these processes. Seamounts are substantial outcrops of the oceanic lithosphere and offer natural laboratories for the study the ecology of microbe/ basaltic glass interactions. Studies of natural rock surfaces and hydrothermal metal-oxy-hydroxides from different hydrothermal settings at Vailulu'u Seamount (American Samoa), resulted in a detailed characterization of microbial communities and the isolation of a large number of metabolically diverse microbes. One of these strains, Pseudomonas stutzeri VS-10, was chosen as a model organism to study the processes of microbe/basaltic glass interactions. It was isolated from a rhyolite microbial trap and exhibits elevated growth under nutrient limited conditions in the presence of basalt. Key metabolic traits of VS-10 include heterotrophic Fe (II)-oxidation and siderophore production. I investigated this strain with respect to a number of metabolic processes, including the oxidative transformation of Fe and Mn, the production of metabolic byproducts (e.g. organic acids) and secondary metabolites (siderophores) along with their effects on the bio-alteration of the glass. Methods employed include Scanning Electron and Atomic Force Microscopy (SEM and AFM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Reversed-phase High Performance Liquid Chromatography (HPLC), Liquid Chromatography Electrospray Ionization Mass Spectrometry (LC-ESI-MS) and microbial fuel cells (MFC). Fe availability and direct contact of the bacterium with the rock surface was shown to significantly facilitate growth of the strain suggesting basaltic glass as an important substratum in supporting metabolically diverse microbial communities in deep-sea ecosystems