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Responses to arsenate stress by Comamonas sp. strain CNB-1 at genetic and proteomic levels

¹ State Key Laboratory of Microbial Resource, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
² Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China

Correspondence
Shuang-Jiang Liu
liusj{at}sun.im.ac.cn
Si-Qi Liu
siqiliu{at}genomics.org.cn

Comamonas sp. strain CNB-1, a chloronitrobenzene-degrading bacterium, was demonstrated to possess higher arsenate tolerance as compared with the mutant strain CNB-2. pCNB1, a plasmid harboured by CNB-1 but not CNB-2, contained the genetic cluster ars(RPBC)_Com, which putatively encodes arsenate-resistance regulator, family II arsenate reductase, arsenite efflux pump and family I arsenate reductase, respectively, in Comamonas strain CNB-1. The arsC-negative Escherichia coli could gain arsenate resistance by transformation with arsP_Com or arsC_Com, indicating that these two genes might express functional forms of arsenate reductases. Intriguingly, when CNB-1 cells were exposed to arsenate, the transcription of arsP_Com and arsC_Com was measurable by RT-PCR, but only ArsP_Com was detectable at protein level. To explore the proteins responding to arsenate stress, CNB-1 cells were cultured with and without arsenate and differential proteomics was carried out by two-dimensional PAGE (2-DE) and MALDI-TOF MS. A total of 31 differential 2-DE spots were defined upon image analysis and 23 proteins were identified to be responsive specifically to arsenate. Of these spots, 18 were unique proteins. These proteins were identified to be phosphate transporters, heat-shock proteins involved in protein refolding, and enzymes participating in carbon and energy metabolism.

Three supplementary figures are available with the online version of this paper.