Cellular responses of Acinetobacter guillouiae SFC500-1A to the simultaneous phenol and Cr(VI) contamination: A proteomic approach

ONTAÑON ORNELLA M.; GONZÁLEZ, PAOLA S; LANDI, CLAUDIA; CARLEO, ALFONSO; GAGLIARDI, ASSUNTA; BINI, LUCA; AGOSTINI ELIZABETH

San Miguel de Tucumán

Simposio; X Simposio Nacional de Biotecnología REDBIO Argentina 2015; 2015

REDBIO

Microbial bioremediation has a great potential to restore contaminated environments. However, the lack of information about factors regulating the microbial growth and metabolism in polluted environments often limits its implementation. This problem worsens when trying to use microorganisms for the remediation of mixtures of toxic substances. In this sense, Acinetobacter guillouiae SFC 500-1A is a strain able to simultaneously detoxify phenol and Cr(VI). Although some mechanisms implied in such process were previously elucidated by our research group, the use of this strain for remediating co-contaminated sites requires a deep understanding of protein components and cellular pathways enabling to tolerate and biotransform these pollutants. Proteomics is a promising tool to address some questions regarding the molecular mechanisms involved in bioremediation. Therefore, the total proteome of A. guillouiae growing in the absence and in the presence of phenol and Cr(VI) was evaluated by 2-D electrophoresis plus MALDI-TOF MS. The results revealed that in the presence of phenol as well as phenol and Cr(VI), all the enzymes involved in phenol degradation were up-regulated, under the control of AraC transcriptional regulator. Some important enzymes catalyzing the transformation of phenol degradation products into intermediates of glyoxylate and methylisocitrate cycles, were also overexpressed, but TCA cycle key enzymes were down-regulated. Probably this behavior tends to stimulate the synthesis of carbon compounds rather than energy production, as a cellular regulation mechanism. Furthermore, indicators of membrane damage and oxidative stress were detected, mostly when the pollutants were simultaneously incorporated, whereas cellular defense proteins like chaperones, peroxiredoxin and catalase were up-regulated. The importance of porins and efflux pumps in the regulation of pollutants content and their metabolic products was also demonstrated. When Cr(VI) was added, two different oxidoreductases were up-expressed, which could be directly implied in Cr(VI) reduction to Cr(III), the main biological mechanism for Cr(VI) detoxification. Therefore, A. guillouiae SFC500-1A would contain the cellular tools to cope with contaminants-induced stress, which could allow their detoxification. These findings constitute an initial attempt to understand the processes triggered in this microorganism, which could help to improve its performance in bioremediation.