Iron -reducing microorganisms

Lovley DR, Phillips EJP (1988) Novel mode of microbial energy metabolism organic carbon oxidation coupled to dissimilatory reduction of iron or manganese. App Environ Microbio 54 1472-1480 Lovley DR, Stolz JF, Nord Jr GL, Phillips EJP (1987) Anaerobic production of magnetite by a dissimilatoiy iron-reducing microorganism. Nature 330 252-254... 

Lovley, D. R., Stolz, J. F., Nord, G. L. Phillips E. J. P. (1987). Anaerobic production of magnetite by dissimilatory iron-reducing microorganisms. Nature, 330, 252-4. 

Liu X, Roe F, Jesaitis A, Lewandoski Z (1998) Resistance of biofilms to the catalase inhibitor 3-amino-1,2,4-triazole. Biotechnol Bioeng 59 156-162 Lovley DR, Stolz JF, Nord GL, Phillips EJ (1987) Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism. Nature (Lond)... 

Lovley, D. and D. Lonergan. 1990. Anaerobic oxidation of toluene, phenol, and / -cresol by the dissimi-latory iron-reducing microorganism GS-15. Appl. Environ. Microbiol. 56 1858-1864. 

DOM can also act as an electron acceptor for biotically mediated oxidation reactions. Many active microorganisms, particularly phototrophs, produce reductants in excess of metabolic needs that must be regenerated by transfering electrons to acceptors in the environment via membrane-spanning reductases (Price and Morel, 1990). It has been discovered that some iron-reducing bacteria use humic and fulvic acids as terminal electron acceptors for their respiratory transport systems (Coates et al., 1998). 

Anaerobic oxidation has also been demonstrated as a pathway for chlorinated ethene degradation. Microorganisms have been shown to oxidize VC to C02 under ferric iron-reducing conditions [43] and DCE has been shown to oxidize directly to C02 under Mn(IV)-reducing conditions [44]. In addition, Bradley [33] reports that VC can be oxidized under methanogenic conditions. Suarez and Rifai [31] report first-order rate constants for the anaerobic oxidation of VC. 

Other microorganisms promote corrosion of iron and its alloys through dissimilatory iron reduction reactions that lead to the dissolution of protective iron oxide/hy dr oxide films on the metal surface. Passive layers are either lost or replaced by less stable films that allow further corrosion. Obuekwe and coworkers [60] evaluated corrosion of mild steel under conditions of simultaneous production of ferrous and sulfide ions by an iron-reducing bacterium. They reported extensive pitting when both processes were active. When only sulfide was produced, initial corrosion... 

Some microorganisms can directly transfer electrons to the electrode via a physical contact of the cell membrane or a membrane organelle with the anode. No diffusional redox species are involved in this electron transfer process. As illustrated in Figure 2.6a, the direct electron transfer requires the microorganisms to possess (1) membrane-bound protein relays which transfer electrons from the inside of the bacterial cell to its outside, and (2) an outer membrane (OM) redox protein which accepts the electrons and delivers them to an external, solid electron acceptor (a metal oxide or an MFC anode). The most studied OM redox proteins are c-type cytochromes, which are involved in metal-reducing microorganisms such as Geobacter, Rhodqferax and Shewanella. These bacteria often have to rely on solid terminal electron acceptors like iron(lll) oxides in their natural environments. 

Evidence of nanowires produced by photosynthetic microorganisms. The production of conductive nanowires has been shown by microorganisms other than iron-reducing bacteria. The capability to produce conductive appendages has also been demonstrated in... 

Under anaerobic conditions, p,p -DDT is converted to p,p -DDD by reductive dechlorination, a biotransfonnation that occurs postmortem in vertebrate tissues such as liver and muscle and in certain anaerobic microorganisms (Walker and Jefferies 1978). Reductive dechlorination is carried out by reduced iron porphyrins. It is carried out by cytochrome P450 of vertebrate liver microsomes when supplied with NADPH in the absence of oxygen (Walker 1969 Walker and Jefferies 1978). Reductive dechlorination by hepatic microsomal cytochrome P450 can account for the relatively rapid conversion of p,p -DDT to p,p -DDD in avian liver immediately after death, and mirrors the reductive dechlorination of other organochlorine substrates (e.g., CCI4 and halothane) under anaerobic conditions. It is uncertain to what extent, if at all, the reductive dechlorination of DDT occurs in vivo in vertebrates (Walker 1974). 

---