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Minerals 2014, 4(1), 74-88; doi:10.3390/min4010074

Membrane Vesicles as a Novel Strategy for Shedding Encrusted Cell Surfaces

1 Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland 2 Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
* Author to whom correspondence should be addressed.
Received: 10 December 2013 / Revised: 24 January 2014 / Accepted: 27 January 2014 / Published: 7 February 2014
(This article belongs to the Special Issue Interactions between Microbes and Minerals)
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Surface encrustation by minerals, which impedes cellular metabolism, is a potential hazard for microbes. The reduction of U(VI) to U(IV) by Shewanella oneidensis strain MR-1 leads to the precipitation of the mineral uraninite, as well as a non-crystalline U(IV) product. The wild-type (WT) strain can produce extracellular polymeric substances (EPS), prompting precipitation of U some distance from the cells and precluding encrustation. Using cryo-transmission electron microscopy and scanning transmission X-ray microscopy we show that, in the biofilm-deficient mutant ∆mxdA, as well as in the WT strain to a lesser extent, we observe the formation of membrane vesicles (MVs) as an additional means to lessen encrustation. Additionally, under conditions in which the WT does not produce EPS, formation of MVs was the only observed mechanism to mitigate cell encrustation. Viability studies comparing U-free controls to cells exposed to U showed a decrease in the number of viable cells in conditions where MVs alone are detected, yet no loss of viability when cells produce both EPS and MVs. We conclude that MV formation is a microbial strategy to shed encrusted cell surfaces but is less effective at maintaining cell viability than the precipitation of U on EPS.
Keywords: biomineralization; uranium; detoxification; cryo-microscopy; spectro-microscopy biomineralization; uranium; detoxification; cryo-microscopy; spectro-microscopy
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Shao, P.P.; Comolli, L.R.; Bernier-Latmani, R. Membrane Vesicles as a Novel Strategy for Shedding Encrusted Cell Surfaces. Minerals 2014, 4, 74-88.

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