Acinetobacter radioresistens S13, a bacterial strain selected for its ability to biodegrade phenol (qphenol = 8.87 mmol/g/h), biosynthesizes, during growth on aromatic carbon sources, a number of proteins which are absent in control conditions (sodium acetate coltures). The aim of the present research was to identify proteins, specifically induced by aromatic substrates (benzoate and/or phenol), having alkaline isoelectric points (between 6 and 11), thus integrating results obtained in previous works (Giuffrida et al., 2001; Pessione et al., 2003), concerning the analysis of auxiliary, citosolic and membrane, proteins with acidic pI (pH 4-7). The comparative proteome analysis showed 25 spots differentially expressed: at present 6 of them have been identified by ESI-MS/MS spectrometry. The biological role of the 6 identified proteins can be led back to 4 classes: 1) Proteins involved in uptake of nutrients inside the cell or in extrusion of toxic molecules (tsp Protease); 2) Proteins involved in attenuation of direct and indirect toxic effects of aromatic molecules on bacterial cells (tsp protease, S2 protein of the 30S ribosomal subunit , pseudouridine synthase subunit); 3) Proteins connected with energy metabolism (soluble transhydrogenase for pyridine cofactors, ATP synthase subunit); 4) Proteins connected with pH homeostatis (glutaminase/asparaginase). These results improved our knowledge on the physiology of this Acinetobacter radioresistens strain by giving new insights on regulation and adaptation mechanisms of bacterial cells to aromatic exposure.
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