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In Situ Environmental Cell–Transmission Electron Microscopy Study of Microbial Reduction of Chromium(VI) Using Electron Energy Loss Spectroscopy

Published online by Cambridge University Press:  02 February 2002

Tyrone L. Daulton ,
Brenda J. Little ,
Kristine Lowe  and
Joanne Jones-Meehan
Tyrone L. Daulton*
Affiliation:
Marine Geosciences Division, Naval Research Laboratory, Stennis Space Center, MS 39529
Brenda J. Little
Affiliation:
Oceanography Division, Naval Research Laboratory, Stennis Space Center, MS 39529
Kristine Lowe
Affiliation:
Chemistry Division, Naval Research Laboratory, Washington, DC 20375
Joanne Jones-Meehan
Affiliation:
Chemistry Division, Naval Research Laboratory, Washington, DC 20375
*
*Corresponding author
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Abstract

Reduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in situ, environmental cell–transmission electron microscopy (EC-TEM) coupled with electron energy loss spectroscopy (EELS). Bacteria from rinsed cultures were placed directly in the environmental cell of the transmission electron microscope and examined under 100 Torr pressure. Bright field EC-TEM images show two distinct populations of S. oneidensis in incubated cultures containing Cr(VI)O42−: those that exhibit low image contrast and heavily precipitateencrusted cells exhibiting high image contrast. Several EELS techniques were applied to determine the oxidation state of Cr associated with encrusted cells. The encrusted cells are shown to contain a reduced form of Cr in oxidation state +3 or lower. These results demonstrate the capability to determine the chemistry and valence state of reduction products associated with unfixed, hydrated bacteria in an environmental cell transmission electron microscope.

Keywords

in situ transmission electron microscopyenvironmental cellelectron energy loss spectroscopyenvironmental cell–transmission electron microscopydissimilatory metal reductionCr(VI) reductionbacteria
Type
Research Article
Information
Microscopy and Microanalysis , Volume 7 , Issue 6 , November 2001 , pp. 470 - 485
Copyright
Copyright © Microscopy Society of America 2001

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