Characterization of the Edwardsiella tarda proteome in response to different environmental stresses

To date, our understanding of protein species is still limited. In the present study, 2-DE based proteomics was used to investigate characteristics of protein species in Edwardsiella tarda, a prokaryocyte cell model. In the E. tarda proteome that was analyzed by 2-DE and mass spectrometry, 661 unique proteins representing 1320 protein spots were identified, accounting for 19.0% of gene-coding proteins of the bacterium. 256 out of the 661 identified proteins have different forms of single proteins, forming 915 protein species. Proteins with higher molecular mass, abundance, proportion of Glu, Ile, Lys, Asn, and lower pI and proportion of Leu, Gln, Arg were more likely to be modified and thus showed more protein species. In addition, proteins with more Glu, Ile, Lys, Asn, Gly and Phe were easily modified by phosphorylation. Further investigation indicated that the most protein species were detected in the bacterium in response to environmental stresses, and approximately half of them showed the ability to cope with multiple environmental stresses. These results have revealed general characteristic features of bacterial protein species, and also provided novel insights into biological significance of the protein species.