Why Sequence Pedomicrobium manganicum?

Pedomicrobium manganicum lives in one of the most hostile environments on the planet, the surface of desert rocks. This ecological niche can expose it within minutes or hours to massive fluctuations in temperature, ultraviolet irradiation, and desiccation. Consequently, its genome must have evolved to encode the diverse physiological capabilities required for survival in this inhospitable environment. This bacterium is also found in aquatic and marine environments, within sediments extracted from deep boreholes and soils. Of particular relevance to the Department of Energy is that it forms a significant part of the bacterial soil population of Uranium Mill Tailing Remedial Action Sites (UMTRAs). It is the only member of that population that has not been examined by genome sequencing.

Moreover, P. manganicum is of interest in bioremediation. It has been used in pilot bioreactor purification plants to assist in the removal of metals, including manganese, from contaminated water. More recently it has been used for the removal of uranium and radium from a uranium mine retention pond in Australia. The ability to live in sites contaminated with radioactive waste and its tolerance to ultraviolet light make it of interest to groups examining radiation tolerance and DNA repair.

P. manganicum is of interest to a surprising range of sciences. It is of great interest to the study of microbial development because it divides by branching rather than by binary fission (as most bacteria do) and because it has a complex internal membrane system. Its role in cave and biofilm formation makes it of interest to geologists as well as biologists. P. manganicum may also be involved in the deposition of gold flakes and veins, which could have implications in the fields of biology, bioremediation, and commercial mining. On desert rocks, it oxidizes manganese metal to manganese oxide, generating a dark patina called desert varnish. The scientific community understands very little about the underlying biology of desert varnish formation. Indigenous peoples have carved this varnish to produce petroglyphs such as those at Petroglyph National Monument. The preservation of this important part of our national heritage falls to the Department of the Interior, and its geologists and archaeologists look on this genome project with enthusiasm.

Looking beyond our own planet, this organism has piqued the interest of NASA's Ames astrobiology group. The ability of P. manganicum to withstand environmental extremes on rock surfaces makes it a model organism for the study of potential life on other bodies in our solar system.

Principal Investigators: Ronald C. Mackenzie (Univ. of Texas, Houston) and Robert D. Barber (Univ. of Wisconsin-Parkside)