Evidence for Biogenic Pyromorphite Formation by the Nematode Caenorhabditis elegans
B.P. Jackson, P.L. Williams, A. Lanzirotti, and P.M. Bertsch
Advanced Analytical Center for Environmental Sciences, Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29803, Department of Environmental Health Science, University of Georgia, Athens, Georgia 30602-2102, and Consortium for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637
The
determination of chemical speciation and spatial distribution is a prerequisite
for a mechanistic understanding of contaminant bioavailability and toxicity
to an organism. We have employed synchrotron X-ray techniques to study
Cu and Pb speciation and spatial distribution in the soil nematode Caenorhabditis
elegans. Nematodes were exposed to each metal ion singly or simultaneously
in solution for 24 h and were then rinsed thoroughly and preserved in
formalin for transportation to the National Synchrotron Light Source.
Experiments were conducted at the microprobe beamline X26A employing a
focused beam of approximately 10 µm in diameter. Nematodes were
mounted in agar gel on Kapton tape. Two-dimensional elemental maps for
Cu- and Pb-exposed nematodes were collected in fluorescence mode. Copper
was homogeneously distributed throughout the body of the nematode, exclusively
in the anterior pharynx region. Detectable localized concentrations of
Pb in C. elegans occurred at aqueous exposure concentrations
of 2.4 µM. Micro X-ray diffraction of these Pb hotspots gave a diffraction
pattern indicating a crystalline Pb solid that was consistent with the
Pb phosphate, pyromorphite. Biogenic inorganic phosphate granule formation
is relatively common in soil invertebrates; however, these phosphates
are typically amorphous, and we beleive that this is the first report
of crystalline pyromorphite formed internally in an organism.
SREL Reprint #2885
Jackson, B. P., P. L. Williams, A. Lanzirotti and P. M. Bertsch. 2005. Evidence for biogenic pyromorphite formation by the nematode caenorhabditis elegans. Environmental Science & Technology 39:5620-5625.
