- Domain: Bacteria
- Phylum: Proteobacteria
- Class: Alpha Proteobacteria
- Order: Rhizobiales
- Family: Hyphomicrobiaceae
- Genus : Pedomicrobium
Description and Significance
Pedomicrobium manganicum are budding hyphal bacterium. The structure of the bacterium is spherical with up to five hyphae per cell . The formation of these hyphae prevent the progeny from being formed near metallic deposits . As a terrestrial extremophile, it inhabits particularly harsh environments such as desert rock surfaces where it is susceptible to large variations in temperature as well as UV radiation. This microbe is most commonly found on desert rock surfaces, but it has also be found in soils, water systems, and various aquatic systems as biofilms . Pedomicrobium manganicum can be used for many bioremediation processes such as removing manganese from water purification systems to the removal of uranium and radium from Uranium Mill Tailing Remedial Action sites .
The genome of Pedomicrobium manganicum has a size of approximately 5Mb  and has a G/C content of 66% [5.] The rich G/C content can be attributed to two underlying reasons. Studies have shown that a higher G/C content correlates to optimal growth temperature . As an extremophile living in desert environments, Pedomicrobium manganicum has a high G/C content which would be more stable at higher temperatures. Another explanation for the rich G/C content would be that higher G/C content correlates to a longer length in coding regions . The number of chromosomes and weather they are circular or linear is unknown . The manganese oxidation operon has been sequenced and has a Genbank Accession number of AM049177 .
Cell Structure, Metabolism and Life Cycle
Pedomicrobium manganicum do not rely on binary fission as their way of division. They produce prosthecas, which are simple budding hyphae, which then form daughter cells . Since this microbe dwells in extreme conditions such as desert rocks, it must be able to survive in severely dry conditions for extended periods of time. In order to survive, Pedomicrobium manganicum maintains cellular hydration by going into an anhydrobiotic state . Anhydrobiosis is the process in which the cell is in an almost completely desiccated state that stabilizes its membranes and other cellular structures, preventing otherwise lethal damage caused by environmental extremes present. Pedomicribium manganicum oxidize manganese enzymatically, and proper enzymatic function is copper dependent for this microbe. Oxidation occurs using a two - step process. First, adsorption of Mn (II) by surface charges to extracellular polysaccharides occurs, which are then oxidized enzymatically . Although it is known that copper dependency is a co- factor for enzyme activity, the underlying mechanism for this has yet to be determined [5,11]. Also, Pedomicrobium manganicum can also bind and deposit preformed manganese oxide. In many water treatment facilities, chlorination is used to oxidize manganese but can be inefficient. Pedomicrobium manganicum were able to bind to the preformed colloidal (microscopically dispersed insoluble particle suspended through the water) manganese oxide and deposit them using extracellular acidic polysaccharides, and tests indicated that optimal binding pH was at 4 .
Ecology and Pathogenesis
Biogeochemical Significance: Pedomicrobium manganicum is known to oxidize manganese.
Contributions to Environment: Within bioreactors of waste water and drinking water systems, this bacteria can be used to oxidize and clean out what can be called "dirty water," an excess of manganese in the water creates a murky look. Removal of manganese to reduce the murkiness of water is not the only role this bacterium plays in the environment. A current public health concern is that high concentrations of manganese in water affects about 8.7 million Americans . To help with this issue, It is used in water supply systems to remove manganese, which at high concentrations ( 14 mg/L) is a neurotoxin [5, 6]. This microbes ability to withstand UV radiation on desert rock surfaces as well as ionized radiation in contaminated soils is gaining the interest of scientists. Pedomicrobium manganicum has been found as making up a large component of the subsurface bacterial population in Uranium Mill Tailing Remedial Action sites (UMTRA). This evidence showed that it is used as a bioremediation tool in cleaning radioactive wastes by removing uranium and radium .
Evolutionary Impact : The deposition of manganese oxides onto desert rock surfaces form desert varnish. Carving into the varnish and removing it by indigenous peoples created petroglyphs. Many petroglyphs are centuries old, and the varnish has not grown back to cover them. This indicates varnish growth through manganese oxide deposits are very slow growing, which led to the fact that the remaining varnish that has not been carved out are some of the most ancient living communities on the planet .
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Page authored by Shuaib Mirani and Derrick Martin, students of Prof. Jay Lennon at IndianaUniversity.