Bioremediation of Cr(VI) and immobilization as Cr(III) by Ochrobactrum anthropi.

Bioremediation of Cr(VI) through reduction relies on the notion that the produced Cr(III) may be precipitated or efficiently immobilized. However, recent reports suggest that soluble organo-Cr(III) complexes are present in various chromate-reducing bacterial systems. This work was designed to explore the factors that affect the immobilization of Cr(III) in the Ochrobactrum anthropi system. X-ray absorption fine structure analysis on the cell debris clearly verified that coordination of Cr(III) occurs on the surfaces via the chelating coordination with carboxyl- and amido-functional groups. However, competitive coordination experiments of Cr(III) revealed that the small molecules such as amino acids and their derivatives or multicarboxyl compounds hold stronger coordination ability with Cr(III) than with cell debris. We speculate that it is the preferential coordination of Cr(III) to the soluble organic molecules in the bacterial culture medium that inhibits effective immobilization of Cr(III) on the cells. On the basis of this understanding, a strategy with two-step control of the medium was proposed, and this achieved successful immobilization of Cr(VI) as Cr(III) by O. anthropi and Planococcus citreus in 5-50 L pilot-scale experiments.

Microbial conversion of 5-sulfoisophthalic acid into 5-hydroxyisophthalic acid by Ochrobactrum anthropi S9.

5-Hydroxyisophthalic acid-producing microorganisms were isolated from enrichment cultures using 5-sulfoisophthalic acid as a sulfur source. One bacterium, Ochrobactrum anthropi S9, had the highest 5-sulfoisophthalic acid-degrading activity, and stoichiometrically formed 5-hydroxyisophthalic acid, a raw material for polymer synthesis. Under optimum culture conditions, 1.3 mM 5-hydroxyisophthalic acid accumulated in the medium by 60 h. The addition of Na(2)SO(4), L: -methionine or L: -cysteine at 2 mM inhibited the conversion of 5-sulfoisophthalic acid. O. anthropi S9 cells converted 5-sulfoisophthalic acid, benzenesulfonic acid, 3-sulfobenzoic acid, 4-aminobenzenesulfonic acid, naphthalene-1-sulfonic acid and naphthalene-2-sulfonic acid into the corresponding hydroxylated compounds.

Reporter genes for real-time in vive monitoring of Ochrobactrum anthropi infection.

Despite the increasing interest in Ochrobactrum anthropi as an emerging nosocomial pathogen resistant to most commonly used antimicrobials, relatively little is known about the pathogenesis and factors contributing to its virulence. Also, many aspects of interaction between Ochrobactrum spp. and their hosts remain unclear. The ability to monitor O. anthropi infection in the host will facilitate our understanding of the pathogenic mechanisms and will lead to better choices of antimicrobial or additional therapeutic strategies. We have demonstrated the ability to stably express three reporter genes (green fluorescence protein GFP, red fluorescence protein RFP and luciferase Lux) and track the infection in a J774A.1 murine macrophage cell line as well as in the BALB/c mouse. Our results suggest that these reporter genes should improve genetic studies in O. anthropi, particularly those aimed at understanding pathogenesis, virulence factors and host interaction.

delta-(D -alpha-Aminoadipoyl)-cleaving amidase of Ochrobactrum anthropi.

Ochrobactrum anthropi cleaved the delta-(D-alpha-aminoadipoyl)-side chain from delta-(D-alpha-aminoadipoyl)-7-amino-4-methylcoumarin, a beta-lactamase-resistant cephalosporin C analogue. In whole cell conversions up to 1 nkat g(-1) dry cell wt were achieved. O. anthropi possesses also gamma-D-glutamyltranspeptidase activity, 8 nkat g(-1) dry cell wt, the likely cause of delta-(D-alpha-aminoadipoyl)-cleavage.