Production of Biodegradable Copolyesters by Alcaligenes eutrophus

ABSTRACT Ralstonia metallidurans CH34 (formerlyAlcaligenes eutrophus CH34) is a soil bacterium characteristic of metal-contaminated biotopes, as it is able to grow in the presence of a variety of heavy metals. R. metalliduransCH34 is reported now to resist up to 6 mM selenite and to reduce selenite to elemental red selenium as shown by extended X-ray absorption fine-structure analysis. Growth kinetics analysis suggests an adaptation of the cells to the selenite stress during the lag-phase period. Depending on the culture conditions, the medium can be completely depleted of selenite. Selenium accumulates essentially in the cytoplasm as judged from electron microscopy and energy-dispersive X-ray analysis. Elemental selenium, highly insoluble, represents a nontoxic storage form for the bacterium. The ability of R. metallidurans CH34 to reduce large amounts of selenite may be of interest for bioremediation processes targeting selenite-polluted sites.

Download Full-text

Effect of the siderophore alcaligin E on the bioavailability of Cd to Alcaligenes eutrophus CH34

Journal of Industrial Microbiology & Biotechnology ◽

10.1038/sj.jim.2900478 ◽

1998 ◽

Vol 20 (1) ◽

pp. 61-68 ◽

Cited By ~ 28

Author(s):

A Gilis ◽

P Corbisier ◽

W Baeyens ◽

S Taghavi ◽

M Mergeay ◽

...

Keyword(s):

Alcaligenes Eutrophus

Download Full-text

Subforms and In Vitro Reconstitution of the NAD-Reducing Hydrogenase of Alcaligenes eutrophus

Journal of Bacteriology ◽

10.1128/jb.180.5.1023-1029.1998 ◽

1998 ◽

Vol 180 (5) ◽

pp. 1023-1029 ◽

Cited By ~ 35

Author(s):

Christian Massanz ◽

Silke Schmidt ◽

Bärbel Friedrich

Keyword(s):

Alcaligenes Eutrophus ◽

Nadh:Ubiquinone Oxidoreductase ◽

Monomeric Form ◽

Structural Genes ◽

Wild Type ◽

Catalytic Function ◽

C Terminus ◽

In Vitro Reconstitution ◽

Reducing Activity

The cytoplasmic, NAD-reducing hydrogenase (SH) of Alcaligenes eutrophus H16 is a heterotetrameric enzyme which contains several cofactors and undergoes a complex maturation during biogenesis. HoxH is the Ni-carrying subunit, and together with HoxY it forms the hydrogenase dimer. HoxF and HoxU represent the flavin-containing diaphorase moiety, which is closely related to NADH:ubiquinone oxidoreductase and mediates NADH oxidation. A variety of mutations were introduced into the four SH structural genes to obtain mutant enzymes composed of monomeric and dimeric forms. A deletion removing most ofhoxF, hoxU, and hoxY led to the expression of a HoxH monomer derivative which was proteolytically processed at the C terminus like the wild-type polypeptide. While the hydrogenase dimer, produced by a strain deleted of hoxF andhoxU, displayed H2-dependent dye-reducing activity, the monomeric form did not mediate the activation of H2, although nickel was incorporated into HoxH. Deletion ofhoxH and hoxY led to the production of HoxFU dimers which displayed NADH:oxidoreductase activity. Mixing the hydrogenase and the diaphorase moieties in vitro reconstituted the structure and catalytic function of the SH holoenzyme.

Download Full-text