Extracellular respiration of different amounts azo dye by Shewanella decolorationis S12 and comparative analysis of the membrane proteome

Shewanella decolorationis S12 is capable of using azo compounds as terminal electron acceptors for respiration. However, knowledge about membrane proteins involved in this biochemical process is still limited. In addition, little is known about cell growth of this species in response to the increasing level of azo dye. In the present study, different culture methods were used to compare the biomass production rates of strain S12 in the presence of a high polarity azo dye, amaranth, as the sole terminal electron acceptor. The use of a fed-batch fermentor culture method allowed a much higher biomass accumulation in the presence of higher amounts of amaranth, compared to static serum bottle culture. Membrane proteome profiles were obtained by two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF/MS) for cells grown with different amounts of amaranth under anaerobic conditions. Three proteins Ndk, ClpP, and ArgC were found in markedly increased abundance in response to the growth increases in the presence of amaranth. Bioinformatics analysis implicated that these three proteins may be involved in azo respiration and energy conservation in strain S12. These findings provide valuable information for better understanding the extracellular azo respiration of S. decolorationis S12.