Changes in morphology, cell wall composition and soluble proteome in Rhodobacter sphaeroides cells exposed to chromate
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The response of the carotenoidless Rhodobacter sphaeroides mutant R26 to chromate stress under photosynthetic conditions is investigated by biochemical and spectroscopic measurements, proteomic analysis and cell imaging. Cell cultures were found able to reduce chromate within 3–4 days. Chromate induces marked changes in the cellular dimension and morphology, as revealed by atomic force microscopy, along with compositional changes in the cell wall revealed by infrared spectroscopy. These effects are accompanied by significant changes in the level of several proteins: 15 proteins were found up-regulated and 15 down-regulated. The protein content found in chromate exposed cells is in good agreement with the biochemical, spectroscopic and microscopic results. Moreover at the present stage no specific chromate-reductase could be found in the soluble proteome, indicating that detoxification of the pollutant proceeds via aspecific reductants.
KeywordsChromate reduction Photosynthesis Rhodobacter sphaeroides Two-dimensional gel electrophoresis Atomic force microscopy Attenuated total reflection-fourier transformed infra red spectroscopy
The authors wish to thank Mr. Giovanni Lasorella for his help with AFM measurements. Paola Nitti, Giacomo Colasuonno and Francesco Di Paolo are gratefully acknowledged. Livia Giotta is thanked for suggestions in the interpretation of ATR-FTIR measurements. Support for this work was obtained by the Italian Ministry of Research Education and Education (Prin 2009) and by COST Action CM0902 Molecular machinery for ion translocation across the membrane.
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