The ability of Shewanella species to respire using sulfate, selenite, and tellurite as electron acceptors motivates us to investigate these metabolically diverse bacteria as a means to synthesize nanostructured chalcogenide materials. Recent studies took advantage of this metabolic versatility to synthesize photoactive arsenic sulfide nanofibers with novel morphologies. However, the mechanism behind crystal growth and the exact role of the cells remain poorly understood. Here we present detailed in situ optical/fluorescence microscopic measurements of nanofiber growth and cellular activity, and provide temperature-dependent growth rates that establish the activation energy for crystal growth. Concentrations of arsenic and sulfur in the medium were measured over the course of nanofiber growth to examine the relationship between growth rate and concentration. We also examine the composition of the nucleation sites using electron microprobe analysis and energy-dispersive spectroscopy. Taken together, the data suggest a biologically influenced mechanism of crystal formation preceding the growth of long nanofibers.

Direct in vivo observation of microbially synthesized nanostructured materials

243rd National Meeting (2012)

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