Plutonium occurs naturally on Earth in trace amounts, but tons of plutonium have been produced in nuclear reactors and the U.
S. Department of Energy has plutonium storage sites
in seventeen states across the U.S.A. Plutonium emits alpha, beta, gamma, and neutron radiation and
isotopes have half-lives as long as 2 x 104 years. Consequently, plutonium is considered to be a potential
carcinogen and mutagen (ToxFAQS: Plutonium). Plutonium has
no known biological function, and research investigating microbial interactions with plutonium has focused on bioremediation
of waste sites and environments contaminated with plutonium.
Plutonium can exist in oxidation states from III to VI under aqueous conditions, and different oxidation states predominate
in different environments (Ibrahim and Culp, 1989). Dissimilatory plutonium
reduction has not been documented, but Rusin et al (1994) reported the
solubilization of plutonium oxides from soil by iron-reducing bacteria, which may represent reductive dissolution of
plutonium. Yong and Macaskie (1998) demonstrated the potential for a Citrobacter sp. expressing
surface phosphatase activity to mineralize Pu(IV) in an insoluble complex with lanthanum and phosphate. Microbacterium
flavescens JG-9 was shown to accumulate Pu(IV) via siderophore-mediated
uptake (John et al, 2001). Aspergillus niger grown on a solid medium containing plutonium
transported plutonium from the medium to aerial spores (Beckert and Au, 1976). Immobilization of soluble plutonium using
bacteria as biosorbents has been explored (Meyer et al, 1979; Panak et al, 2001).
For more information:
Medline for plutonium metabolism AND bacteria
Beckert WF, Au FHF. Plutonium uptake by a soil fungus and transport to its spores. Transuranium Nuclides in the Environment,
Proc. Symp. 1976;337-45.
Yong P, Macaskie LE. bioaccumulation of lanthanum, uranium and thorium, and use of a model system to develop a method for
the biologically-mediated removal of plutonium from solution. J. Chem. Technol. Biotechnol. 1998;71:15-26.
Panak PJ, Nitsche H. Interaction of aerobic soil bacteria with plutonium(VI). Radiochim. Act. 2001;89:499-504.
Rusin PA, Quintana L, Brainard JR, Strietelmeier BA, Tiat CD, Ekberg SA, Palmer PD, Newton TW, Clark DL. Solubilization of
plutonium hydrous oxide by iron-reducing bacteria. Environ. Sci. Technol. 1994;28:1686-90.