Microbial Diversity And Evidence For Bacterially Mediated Basalt Dissolution On Vailulu'u Seamount

In the deep ocean, seamounts are one of the most common topographic features and their role as highly productive centers of biodiversity was discovered in the last decades. Together with mid-ocean ridge and back- arc systems, seamounts are the main source of basaltic glass, volcanic rocks highly enriched in the reduced forms of bio-essential elements such as Mn and Fe (Mn(II) and Fe(II)). Weathering of these rocks takes place through ion exchange mechanisms resulting in a significant change in rock and local oceanic chemistry. These processes can be significantly enhanced by the activity of chemolithotrophic bacteria such as Fe(II)- and Mn(II)-oxidizers. The extent to which microbes are able to use basalt to satisfy their energy and/or nutrient needs as well as the mechanisms of microbial basalt dissolution are not well understood. We have used molecular techniques such as 16S rDNA libraries, t-RFLP and FISH analysis to investigate microbial interactions with Fe and Mn and microbial diversity in different samples (e.g., basalt surfaces, Fe-oxide mats) collected from Vailulu'u Seamount. Culture-based studies were also conducted to provide information on the diversity of Fe- and Mn-oxidizing strains, their physiological features, and the complexity of mechanisms potentially involved in microbial basalt dissolution. Studies have been carried out with one model Fe(II)- oxidizing bacterium to identify and understand the primary and any secondary mechanisms of Fe acquisition that might allow the use of basaltic glass as a source of nutrients and energy.