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Changes in protein expression in Burkholderia vietnamiensis PR1₃₀₁ at pH 5 and 7 with and without nickel

Joy D. Van Nostrand^1,

¹ Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, 221 Fort Johnson Rd, Charleston, SC 29412, USA
² Department of Medicine, Medical University of South Carolina, PO Box 250623, Charleston, SC 29425, USA
³ NIST, Hollings Marine Laboratory, 331 Fort Johnson Rd, Charleston, SC 29412, USA
⁴ University of Kentucky, Department of Plant and Soil Sciences, 1405 Veterans Drive, Lexington, KY 40546, USA
⁵ Department of Cell Biology and Anatomy, Medical University of South Carolina, PO 173 Ashley Avenue, Charleston, SC 29425, USA
⁶ National Ocean Service, Hollings Marine Laboratory, 331 Fort Johnson Rd, Charleston, SC 29412, USA

Correspondence
Pamela J. Morris
morrisp{at}musc.edu

Burkholderia vietnamiensis PR1₃₀₁ (PR1) exhibits pH-dependent nickel (Ni) tolerance, with lower Ni toxicity observed at pH 5 than at pH 7. The Ni tolerance mechanism in PR1 is currently unknown, and traditional mechanisms of Ni resistance do not appear to be present. Therefore, 2D gel electrophoresis was used to examine changes in protein expression in PR1 with and without Ni (3.4 mM) at pH 5 and 7. Proteins with both a statistically significant and at least a twofold difference in expression level between conditions (pH, Ni) were selected and identified using MALDI-TOF-MS or LC-MS. Results showed increased expression of proteins involved in cell shape and membrane composition at pH 5 compared with pH 7. Scanning electron microscopy indicated elongated cells at pH 5 and 6 compared with pH 7 in the absence of Ni. Fatty acid methyl ester analysis showed a statistically significant difference in the percentages of long- and short-chain fatty acids at pH 5 and 7. These findings suggest that changes in membrane structure and function may be involved in the ability of PR1 to grow at higher concentrations of Ni at pH 5 than at pH 7.

Present address: University of Oklahoma, Institute for Environmental Genomics, 101 David L Boren Blvd, Norman, OK 73019, USA.

Representative growth curves and additional 2D gels, details of proteins identified by MALDI-TOF-TOF and LC-MS/MS and further details of differential expression are available as supplementary material with the online version of this paper.