Microbiology of a reclaimed uranium mine

Research by Olivia Chavez, who completed her master’s degree with Dr. Tom Kieft, New Mexico Tech Biology Department, in 2016.This research is one of several Energize New MexicoEPSCoR projects focusing on uranium mineralization and mine-site remediation.

Microbes can play an important role in geology and in the precipitation and dissolution of mineral components. Uranium is most commonly mobile in the environment with a charge of 6+, referred to as oxidized uranium, usually forming the uranyl molecule, UO₂²⁺. It is most commonly precipitated with the oxidation state of 4+, referred to as reduced uranium, to form minerals as the molecule U₃O₈. Microbes, which are constantly seeking metals and molecules that they can use as nutrients, energy sources, and electron acceptors, often reduce such metal species (changing uranium 6+ as UO₂²⁺ to uranium 4+ as U₃O₈, for example) as part of their metabolic processes; however, not all microbes reduce all metal species. Identifying microbes that can reduce the uranyl molecule and therefore create an environment ripe for uranium precipitation could be important for understanding how uranium deposits occur and for identifying possible tools for uranium mine remediation. This study attempted to identify the microbial species present in the soils of a remediated uranium mine in an arid environment and to use molecular techniques to identify microbial functional groups (i.e., those parts of microbes at a molecular level that do the chemical work) that can reduce uranium ions. It is one of the first studies to characterize microbial communities at a reclaimed uranium mine, in this case the Jackpile Mine at Laguna Pueblo, and it plays an important role characterizing the microbial community in such an environment.

Several results of this study are listed below:

1. The sites sampled had very similar microbial communities to other arid New Mexico soil microbial communities.
2. The soil samples at this mine site show less microbial diversity than New Mexico soils undisturbed by mining.
3. The abundance of three genera of microbes seems to be controlled by the heavy metals selenium, nickel and zinc.
4. The metal-reducing genus Geobacter, among other genera, was present in the soils in relative abundance.

New Mexico EPSCoR (Experimental Program to Stimulate Competitive Research) is intended to improve the state’s ability to do scientific research. It is funded by National Science Foundation (NSF) award #IIA-1301346.

References

1. Chavez, O. R., 2016, Microbiology of a reclaimed uranium mine, Laguna Pueblo, NM, unpublished Masters of Science Thesis, New Mexico Institute of Mining & Technology, 40p. [posted with the permission of the author]