Obligate anaerobes observations

Although under chemolithoautotrophic growth conditions, cell densities of only 3-5 x 10 cells per milliliter were observed, the specific rate of Fe(III) reduced per cell unit was about 10 times faster than what had been published for any other Fe(lll) reducer. This strengthens the hypothesis that microbially mediated Fe(III) reduction by obligately anaerobic thermophiles could have been an important process on early Earth, when elevated temperatures were predominant (Baross 1998 Kashefi and Lovley 2000), which includes the involvement in the formation of specific Banded Iron Formations. In light of the properties of the above Fe(lll) reducers, the theories on the origin and biogeochemistry of Banded Iron Formations should be revisited. 

It has recently been found that obligately anaerobic microbial consortia can mineralize many recalcitrant chemicals (toluene, chloroform, benzene, chlorophenols, etc.) that had been considered essentially nonbiodegradable in the absence of oxygen (19, 20, 21). Extensive work at the University of Idaho with obligately anaerobic microbial consortia indicates that these systems are capable of complete biodegradation of nitroaromatic pollutants. Work with 2-.s c-butyl-4,6-dinitrophenol (dinoseb) has shown complete fermentation of this nitroaromatic pollutant in soils by anaerobic consortia without buildup of aromatic biotransformation products (16, 17). Similar results were observed with a variety of nitro-toluenes and munitions residues, including TNT and trimethylenenitramine (RDX) under appropriately controlled conditions (12, 13). In the work with TNT and RDX, hydroxyaro-... 

This was our first observation of a defined, obligately anaerobic culture that could degrade TNT provided as a source of carbon and nitrogen. The culture converted TNT to a mixture of volatile organic acids and a small amount of carbon dioxide via a fermentative pathway apparently differing from that of most Clostridium species by producing at least five different organic acids from the seven-carbon TNT molecule. 

While H. chlorum tolerates exposure to high light intensities well, it is extremely sensitive to oxygen and grows only as a strict anaerobe [63]. Physiologically it is an obligate photoheterotroph, since no respiratory metabolism has been observed. Autotrophic CO2 fixation is not sustained by either hydrogen or sulfide [63]. 

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