Modulation of the glutathione S-transferase in Ochrobactrum anthropi: function of xenobiotic substrates and other forms of stress

Abstract

The gluthathione S-transferase gene of the atrazine-degrading bacterium Ochrobactrum anthropi (OaGST) encodes a single-subunit polypeptide of 201 amino acid residues (Favaloro et al. 1998, Biochem. J. 335, 573-579). RNA blot analysis showed that the gene is transcribed into an mRNA of about 800 nucleotides, indicating a monocistronic transcription of the OaGST gene. The modulation of OaGST in this bacterium, in the presence of different stimulants, was investigated. The level of expression of OaGST was detected both by measuring the mRNA level and by immunoblotting experiments. OaGST is a constitutive enzyme which is also inducible by several stimulants. In fact, atrazine caused an increase in the expression of OaGST even at concentrations which had no effect on growth rates of the bacteria. Moreover, the presence of other aromatic substrates of this bacterium, such as phenol and chlorophenols, leads to a marked enhancement in OaGST expression. In this case, the expression of OaGST was related to growth inhibition and membrane damage caused by these hydrophobic compounds, and to the adaptive responses of the cell membranes. On the other hand, toluene and xylene, two aromatic compounds not degradable by this bacterium, did not induce the OaGST expression. The same was observed for other stress conditions such as low pH, heat shock, hydrogen peroxide, osmotic stress, starvation, the presence of aliphatic alcohols or heavy metals. These results suggest a co-regulation of the OaGST gene by the catabolic pathways of phenols and chlorophenols in this bacterium. Therefore, OaGST could function as a detoxifying agent within the catabolism of these xenobiotics.

Insights into the genome and proteome of Sphingomonas paucimobilis strain 20006FA involved in the regulation of polycyclic aromatic hydrocarbon degradation

“…The enzyme GST was found overexpressed in phenanthrenecontaining cultures in comparison to cultures with glucose. The upregulation of GST had also been reported for other PAH-stressed Sphingomonas strains (Cavalca et al 2007;Xia et al 2005) and is in agreement with the production of oxidative damage by oxygenases involved in the degradation of xenobiotics (Favaloro et al 2000).…”

Adaptations to High Salt in a Halophilic Protist: Differential Expression and Gene Acquisitions through Duplications and Gene Transfers

“…Expression of genes involved in ROS detoxification, several of which, like SOD and peroxidase, were very abundantly transcribed at high salt by H. seosinensis , suggested that ROS level was higher at high salt and that this ROS detoxification ability likely contributes to the organism's tolerance of hypersaline conditions. These included genes coding for proteins related to enzymes linked to increased resistance to oxidative stress, for example those of the alkylhydroperoxidase family (Hillas et al, 2000; Paterson et al, 2006) and Beta class glutathione transferases (Favaloro et al, 2000; Allocati et al, 2003; Tamburro et al, 2004). …”

Bacterial peptide methionine sulphoxide reductase: co-induction with glutathione S-transferase during chemical stress conditions

“…To evaluate the possible co-induction of MsrA with the GST gene, which has been demonstrated previously to be monocistronically transcribed and induced only by chemical stress [24], we determined the transcript size of the MsrA gene and the modulation of its mRNA. Total RNA from O. anthropi cultivated in minimal medium with succinate as carbon source and in the presence of various stimulants (e.g.…”

“…MsrA is a constitutive enzyme which is also inducible by chemical stress involving phenolic compounds such as phenol and 4-chlorophenol. Recently we reported that the GST of this bacterium, like MsrA, is only modulated by toxic chemical compounds [Favaloro, Tamburro, Trofino, Bologna, Rotilio and Heipieper (2000) Biochem. J.…”

“…In this study we use as a prokaryotic model Ochrobactrum anthropi, a bacterium isolated from soil contaminated by xenobiotic pollutants [22]. This bacterium contains a GST enzyme [23], a phase II enzyme of the detoxification system, that is modulated by xenobiotics [24]. A gene homologous to MsrA was identified, located just downstream of the GST gene.…”