Manufacturing and characterization of Pd nanoparticles formed on immobilized bacterial cells.

AIMS: To fabricate and analyse Pd nanoparticles on immobilized bacterial cells. METHODS AND RESULTS: Biological ceramic composites (biocers) were used as a template to produce Pd(0) nanoparticles. The metal-binding cells of the uranium mining waste pile isolate, Bacillus sphaericus JG-A12 were used as a biological component of the biocers and immobilized by using sol-gel technology. Vegetative cells and surface-layer proteins of this strain are known to bind high amounts of Pd(II) that can be reduced to Pd(0) particles by the addition of a reducing agent. Sorption of Pd(II) by the biocers from a metal complex solution was studied by inductively coupled plasma mass spectroscopy analyses. After embedding into sol-gel ceramics, the cells retained their Pd(II)-binding capability. Pd(0) nanoclusters were produced by the addition of hydrogen as reducing agent after the sorption of Pd(II). The interactions of Pd(0) with the biocers and the formed Pd(0) nanoparticles were investigated by extended X-ray absorption fine structure spectroscopy. The particles had a size of 0.6-0.8 nm. CONCLUSIONS: Bacterial cells that were immobilized by embedding into sol-gel ceramics were used as a template to produce Pd nanoclusters of a size smaller than 1 nm. These particles possess interesting physical and chemical properties. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of embedded bacterial cells as template enabled the fabrication of immobilized Pd(0) nanoparticles. These particles are highly interesting for technical applications, such as the development of novel catalysts.

Metal binding by bacteria from uranium mining waste piles and its technological applications.

Uranium mining waste piles, heavily polluted with radionuclides and other toxic metals, are a reservoir for bacteria that have evolved special strategies to survive in these extreme environments. Understanding the mechanisms of bacterial adaptation may enable the development of novel bioremediation strategies and other technological applications. Cell isolates of Bacillus sphaericus JG-A12 from a uranium mining waste pile in Germany are able to accumulate high amounts of toxic metals such as U, Cu, Pb, Al, and Cd as well as precious metals. Some of these metals, i.e. U, Cu, Pd(II), Pt(II) and Au(III), are also bound by the highly orderd paracrystalline proteinaceous surface layer (S-layer) that envelopes the cells of this strain. These special capabilities of the cells and the S-layer proteins of B. sphaericus JG-A12 are highly interesting for the clean-up of uranium contaminated waste waters, for the recovery of precious metals from electronic wastes, and for the production of metal nanoclusters. The fabricated nanoparticles are promising for the development of novel catalysts. This work reviews the molecular biology of the S-layer of the strain JG-A12 and the S-layer dependent interactions of the bacterial cells with metals. It presents future perspectives for their application in bioremediation and nanotechnology.

Transformation of chlorinated benzenes and toluenes by Ralstonia sp. strain PS12 tecA (tetrachlorobenzene dioxygenase) and tecB (chlorobenzene dihydrodiol dehydrogenase) gene products.

The tecB gene, located downstream of tecA and encoding tetrachlorobenzene dioxygenase, in Ralstonia sp. strain PS12 was cloned into Escherichia coli DH5alpha together with the tecA gene. The identity of the tecB gene product as a chlorobenzene dihydrodiol dehydrogenase was verified by transformation into the respective catechols of chlorobenzene, the three isomeric dichlorobenzenes, as well as 1,2,3- and 1,2,4-trichlorobenzenes, all of which are transformed by TecA into the respective dihydrodihydroxy derivatives. Di- and trichlorotoluenes were either subject to TecA-mediated dioxygenation (the major or sole reaction observed for the 1,2,4-substituted 2,4-, 2,5-, and 3,4-dichlorotoluenes), resulting in the formation of the dihydrodihydroxy derivatives, or to monooxygenation of the methyl substituent (the major or sole reaction observed for 2,3-, 2,6-, and 3,5-dichloro- and 2,4,5-trichlorotoluenes), resulting in formation of the respective benzyl alcohols. All of the chlorotoluenes subject to dioxygenation by TecA were transformed, without intermediate accumulation of dihydrodihydroxy derivatives, into the respective catechols by TecAB, indicating that dehydrogenation is no bottleneck for chlorobenzene or chlorotoluene degradation. However, only those chlorotoluenes subject to a predominant dioxygenation were growth substrates for PS12, confirming that monooxygenation is an unproductive pathway in PS12.

Triterpenoid saponins from the roots of Zygophyllum species.

Two new triterpenoid saponins, 3-O-[beta-D-2-O-sulphonylglucopyranosyl]-quinovic acid-28-O-[beta-D-glucopyranosyl] ester (zygophyloside G), 3-O-[alpha-L-arabinopyranosyl-(1-->2)-beta-D-quinovopyranosyl++ +]-quinovic acid-28-28-O-[beta-D-glucopyranosyl] ester (zygophyloside H), and seven known saponins have been isolated. The structures were established primarily on the basis of NMR spectroscopy. The assignment of all NMR signals was performed by means of 1H-1H COSY-45, NOESY, TOCSY, 13C APT, HMQC and HMBC experiments. The determination of the glycosylation sites was possible by the HMBC experiments.

A comparison of two buffering systems for lens organ culture.

Bovine lenses were incubated in a pairwise assay for 24 h in TC 199 which was buffered with Hepes or NaHCO3, respectively. In lenses incubated with Hepes, the content of ATP was higher and that of AMP lower than in those incubated with NaHCO3. The specific activity of phosphofructokinase (PFK), was higher in the lenses from the Hepes medium than in lenses incubated with NaHCO3. A heat-labile metazyme of the PFK which is found in the nucleus of unincubated lenses disappeared when the lenses were incubated in the presence of bicarbonate, but remained intact after 22 h incubation with Hepes.