Gel sequestration of heavy metals by Klebsiella oxytoca isolated from iron mat

Abstract

The enterobacterium Klebsiella oxytoca strain BAS-10 was isolated from sediments under an iron mat formed in a stream receiving leached waters from pyrite mine tailings. Under anaerobic laboratory conditions, BAS-10 fermented Fe(III)-citrate and Na-citrate giving CH(3)COOH and CO(2). In the presence of ferric citrate, BAS-10 secreted quantities of a thick gel containing glucose and/or mannose, if not other sugars. Sugar residues were observed in microbial aggregates using the sugar-specific concanavalin A lectin conjugated with fluorescein and imaged by a scanning confocal laser microscope. The gel bound Fe(III) which quickly precipitated. During fermentation, however, half the initial Fe(III) concentration was reduced to Fe(II) which did not bind to the gel and remained in solution. BAS-10 showed a high tolerance to heavy metals. Its growth was not inhibited by 1 mM Zn-, Pb- or Cd-acetate. These cations also co-precipitated with the iron gel, suggesting a possible application of this strain for abatement of toxic metals under anaerobic conditions.

A bio-generated Fe(iii)-binding exopolysaccharide used as new catalyst for phenol hydroxylation

“…Several years ago, a strain of Klebsiella oxytoca BAS-10 was isolated from the acid mine drainage of pyrite mines. 15 This strain produces an exopolysaccharide (EPS) during citrate fermentation, and this tricarboxylic acid is transported into the cell through a sodiumdependent carrier coupled to proton efflux by producing acetate at the end of fermentation.…”

Iron-Reducing Bacteria and Iron Nanostructures

“…Nanocrystals have large surface to volume ratio which results in large reactive surface areas for biochemical reactions and hence increase the bioavailability of iron compounds. The surface structure of KCl, 0.1 g; NaH 2 PO4, 1 g; NH 4 Cl, 1.5 g; NaHCO 3 , 2.5 g; ferric citrate, 0.5 mM; mineral solution, 10 ml; vitamin solution, 10 ml [19] NaHCO 3 , 2.5 g, NH 4 Cl, 1.5 g, NaH 2 PO 4 , 0.6 g, KCl, 0.1 g, ferric citrate, 50 mM; vitamin mixture, 10 mL; mineral mixture, 10 mL [10] iron nanoparticles differs from those of larger crystallites which leads to altered reactivity or varied crystal chemistry [44]. For instance, the size-dependent bioavailability of hematite (α-Fe 2 O 3 ) nanoparticles to obligate aerobic Pseudomonas mendocina bacteria was examined by using the natural siderophore-producing wild type strain and a siderophore mutant strain.…”

“…The cultivation is usually performed in the dark or under dim light at room temperature and under protected atmosphere against oxygen. Under aerobic conditions, bacterial growth depends on appropriate transport system and a functional tricarboxylic acid cycle [10,22].…”

“…For instance, some researchers have used a vitamin and mineral mixture enriched media for cultivation of Klebsiella oxytoca. The media was supplemented with 50 mM of ferric citrate which provides ferric ions as electron acceptor and also citrate as organic substrate for fermentation [10,19]. The bacteria consume citrate as energy and carbon sources in anaerobic culture condition [8][9][10].…”

“…From gram staining point of view IRB are not restricted in one category and both gram-positive and gram-negative bacteria can be found among them [5][6][7][8][9][10]. This group of bacteria is now so divergent and belong to gamma and delta Proteobacteria including verity of genus and species such as Stenotrophomonas maltophilia, Brachymonas denitrificans, Paracolobacterum aerogenoides, Serratia marcescens, Aerobacter aerogenes, Citrobacter freundii, Bacillus circuhzns, Bacillus polymyxa, Bacillus alvei, Bacillus cereus, Bacillus pumilus, Bacillus subtilis, Bacillus cereus, Bacillus sphaericus, Pseudomonas aeruginosa, Pseudomonas denitrificans, Pseudomonas stutzeri, Pseudomonas fluorescens, and Pseudomonas putida [11][12][13].…”