Molecular analysis of two bacterioferritin genes, bfralpha and bfrbeta, in the model rhizobacterium Pseudomonas putida KT2440.

The model rhizobacterium Pseudomonas putida KT2440 and other fluorescent pseudomonads possess two bacterioferritins, Bfralpha and Bfrbeta. However, the regulatory systems controlling the expression of these genes and the roles of these proteins in iron homeostasis are ill defined. Our studies show that both bfralpha and bfrbeta were monocistronic: promoter motifs and transcriptional start sites were identified, and Fur boxes and sigma(S)-dependent regulatory motifs were absent.

X-ray absorption near edge structure study of lead sorption on phosphate-treated kaolinite.

Presorbed phosphate significantly increases Pb sorption on the phyllosilicate kaolinite in the pH range from 4to 8. The sorbed Pb-to-P molar ratios over this pH range stray little from the molar ratio found in the mineral pyromorphite, suggesting sorbed phosphate reacts with soluble Pb to form a surface precipitate similar to pyromorphite. X-ray absorption near edge structure (XANES) studies at the Pb L3-edge support this interpretation.

Simultaneous analysis of bacterioferritin gene expression and intracellular iron status in Pseudomonas putida KT2440 by using a rapid dual luciferase reporter assay.

A dual luciferase reporter (DLR) system utilizing firefly and Renilla luciferases was developed and tested in a model rhizobacterium, Pseudomonas putida KT2440. The DLR was applied to simultaneously analyze expression of three putative bacterioferritin genes (bfralpha, bfrbeta, and bfr) and assess the cellular iron status of strain KT2440 by monitoring expression of the Fur-regulated fepA-fes promoter. The DLR proved to be reproducible and sensitive.

Complexation of mercury(II) in soil organic matter: EXAFS evidence for linear two-coordination with reduced sulfur groups.

The chemical speciation of inorganic mercury (Hg) is to a great extent controlling biologically mediated processes, such as mercury methylation, in soils, sediments, and surface waters. Of utmost importance are complexation reactions with functional groups of natural organic matter (NOM), indirectly determining concentrations of bioavailable, inorganic Hg species. Two previous extended X-ray absorption fine structure (EXAFS) spectroscopic studies have revealed that reduced organic sulfur (S) and oxygen/ nitrogen (O/N) groups are involved in the complexation of Hg(II) to humic substances extracted from organic soils.

Isolation of soil bacteria adapted to degrade humic acid-sorbed phenanthrene.

The goal of these studies was to determine how sorption by humic acids affected the bioavailability of polynuclear aromatic hydrocarbons (PAHs) to PAH-degrading microbes. Micellar solutions of humic acid were used as sorbents, and phenanthrene was used as a model PAH. Enrichments from PAH-contaminated soils established with nonsorbed phenanthrene yielded a total of 25 different isolates representing a diversity of bacterial phylotypes.