Corynebacterium glutamicum as an indicator for environmental cobalt and silver stress--a proteome analysis.

Cobalt and silver are toxic for cells, but mechanisms of this toxicity are largely unknown. Analysis of Corynebacterium glutamicum proteome from cells grown in control and cobalt or silver enriched media was performed by two dimensional gel electrophoresis (2DE) followed by mass spectrometry. Our results indicate that the cell adapted to cobalt stress by inducing five defense mechanisms: Scavenging of free radicals, promotion of the generation of energy, reparation of DNA, reparation and biogenesis of Fe-S cluster proteins and supporting and reparation of cell wall. In response to the detoxification of Ag+ many proteins were up-regulated, which involved reparation of damaged DNA, minimizing the toxic effect of reactive oxygen species (ROS) and energy generation. Overexpression of proteins involved in cell wall biosynthesis (1,4-alpha-glucan branching enzyme and nucleoside-diphosphate-sugar epimerase) upon cobalt stress and induction of proteins involved in energy metabolism (2-methylcitrate dehydratase and 1, 2-methylcitrate synthase) upon silver demonstrate the potential of these enzymes as biomarkers of sub-lethal Ag+ and Co toxicity.

A proteome analysis of the cadmium and mercury response in Corynebacterium glutamicum.

Cadmium and mercury are well-known toxic heavy metals, but the basis of their toxicity is not well understood. In this study, we analyzed the cellular response of Corynebacterium glutamicum to sublethal concentrations of cadmium and mercury ions using 2-DE and MS. Mercury induced the over-expression of 13 C. glutamicum proteins, whereas 35 proteins were induced, and 8 proteins were repressed, respectively, under cadmium stress. The principal response to these metals was protection against oxidative stress, as demonstrated by upregulation of, e.g., Mn/Zn superoxide dismutase. Thioredoxin and oxidoreductase responded most strongly to cadmium and mercury. The increased level of heat-shock proteins, enzymes involved in energy metabolism, as well as in lipoic acid and terpenoid biosynthesis after the treatment of cells with cadmium was also registered. Identification of these proteins and their mapping into specific cellular processes enable a global understanding of the way in which C. glutamicum adapts to heavy-metal stress and may help to gain deeper insight into the toxic mechanism of these metals.

A proteome analysis of Corynebacterium glutamicum after exposure to the herbicide 2,4-dichlorophenoxy acetic acid (2,4-D).

The herbicide 2,4-dichlorophenoxy acetic acid (2,4-D) induces a wide spectrum of toxic responses in living organisms. In this study, we analyzed the stress-induced responses of Corynebacterium glutamicum cells on protein level upon treatment with 2,4-D. For this, growing C. glutamicum cells were exposed to sublethal concentrations of 2,4-D, and changes of the gene expression profiles in comparison to non-exposed organisms were analyzed by two-dimensional gel electrophoresis and mass spectrometry. 2,4-D induced the over-expression of at least six C. glutamicum proteins, four of which could be identified by MALDI-TOF-MS. One protein (Cg2521; long-chain acyl-CoA synthetase) was related to the energy metabolism, and two proteins were involved in cell envelope synthesis (Cg2410; glutamine-dependent amidotransferase, and Cg1672; glycosyltransferase). The last induced protein was the ABC type transport system (Cg2695, ATPase component). The newly observed proteins, except for the ABC transport system, were not in general stress-related proteins, but were specifically expressed upon 2,4-D exposure and, therefore, can be used as respective biomarkers. Moreover, since these proteins seem to play a pivotal role in the adaptation of the cell to 2,4-D, they may help to gain deeper insight into the damage mechanisms of 2,4-D induced in the living cell.