title: Isolation and characterization of an NAD+-degrading bacterium PTX1 and its role in chromium biogeochemical cycle.
abstract: Microorganisms can reduce toxic chromate to less toxic trivalent chromium [Cr(III)]. Besides Cr(OH)(3) precipitates, some soluble organo-Cr(III) complexes are readily formed upon microbial, enzymatic, and chemical reduction of chromate. However, the biotransformation of the organo-Cr(III) complexes has not been characterized. We have previously reported the formation of a nicotinamide adenine dinucleotide (NAD(+))-Cr(III) complex after enzymatic reduction of chromate. Although the NAD(+)-Cr(III) complex was stable under sterile conditions, microbial cells were identified as precipitates in a non-sterile NAD(+)-Cr(III) solution after extended incubation. The most dominant bacterium PTX1 was isolated and assigned to Leifsonia genus by phylogenetic analysis of 16S rRNA gene sequence. PTX1 grew slowly on NAD(+) with a doubling time of 17 h, and even more slowly on the NAD(+)-Cr(III) complex with an estimated doubling time of 35 days. The slow growth suggests that PTX1 passively grew on trace NAD(+) dissociated from the NAD(+)-Cr(III) complex, facilitating further dissociation of the complex and formation of Cr(III) precipitates. Thus, organo-Cr(III) complexes might be an intrinsic link of the chromium biogeochemical cycle; they can be produced during chromate reduction and then further mineralized by microorganisms.
authors: School of Molecular Biosciences, Washington State University, Abelson Hall 301, Pullman, WA 99164-4234, USA.
authors: Geoffrey J
authors: GJ
authors: Puzon
authors: Yan
authors: Y
authors: Huang
authors: Alice
authors: A
authors: Dohnalkova
authors: Luying
authors: L
authors: Xun
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D001669:Biochemical Phenomena; D001671:Biochemistry; D002857:Chromium / Q000737:chemistry* / Q000378:metabolism*; D018942:Macrolides; D046529:Microscopy, Electron, Transmission; D009243:NAD / Q000378:metabolism*; D010802:Phylogeny; D011714:Pyrans / Q000302:isolation & purification* / Q000378:metabolism*; D013053:Spectrophotometry; D000095702:Polyether Toxins
chemical_list: D002857:Chromium; D018942:Macrolides; D009243:NAD; D011714:Pyrans; C051905:pectenotoxin 1; D000095702:Polyether Toxins