Date of Award

2010-01-01

Degree Name

Master of Science

Department

Environmental Science and Engineering

Advisor(s)

David M. Borrok

Abstract

Copper isotopes may prove to be a useful tool for investigating bacteria-metal interactions recorded in natural waters, soils, and rocks. However, experimental data that constrain Cu isotope fractionation in biologic systems are limited and unclear. In this study we utilized Cu isotopes (65Cu) as a tool to investigate Cu-bacteria interactions, including surface adsorption and intracellular incorporation. Experiments were conducted with individual Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial species as well as with bacterial consortia from several natural environments. Adsorption experiments were conducted with live or dead cells over the pH range 2.5 to 6. Surface adsorption of Cu onto live bacteria cells resulted in apparent separation factors (Δ65Cusolution-solid = 65Cusolution - 65Cusolid) ranging from +0.3 / to +1.4 / for B. subtilis and +0.2 / to +2.6 / for E. coli. The preference of the lighter Cu isotope by the cells appears to be metabolically-driven, as heat-killed bacterial cells did not significantly fractionate Cu isotopes. For the intracellular incorporation experiments, all bacteria and consortia were grown in a basal media amended with Cu(II)-citrate. The bacteria and consortia preferentially incorporated the lighter Cu isotope with an apparent Δ65Cusolution-solid ranging from ~ +1.0 / to +4.4 /. Our results indicate that live bacterial cells preferentially sequester the lighter Cu isotope regardless of the experimental conditions. The mechanisms involved are likely related to the active cellular transport and regulation of Cu. Hence, Cu isotopes may prove to be a powerful chemical tool for probing molecular-scale bacteria-Cu interactions. Cu isotopes in natural systems may also be used to distinguish microbial activity from abiotic geochemical reactions.

Language

en

Provenance

Received from ProQuest

File Size

45 pages

File Format

application/pdf

Rights Holder

Jesica Urbina Navarrete

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