Comparison of Protein Expression Profiles of Novel <i>Halomonas smyrnensis</i> AAD6<sup>T</sup> and <i>Halomonas salina</i> DSMZ 5928<sup>T</sup>

In this work, the protein pattern of novel Halomonas smyrnensis AAD6T was compared to that of Halomonas salina DSMZ5928T, which is the closest species on the basis of 16S rRNA sequence, to understand how AAD6T differs from type strains. Using high resolution NEPHEGE technique, the whole cell protein composition patterns of both Halomonas salina DSMZ5928T and H. smyrnensis AAD6T were mapped. The expressed proteins of the two microorganisms were mostly located at the acidic side of the gels, at molecular weight values of 60 to 17 kDa, and at isoelectric points 3.8 to 6.0, where they share a significant number of common protein spots. Identification and characterization of protein spots via whole genome sequencing data indicated that these two microorganisms used similar pathways, especially TCA cycle, for their survival; in other words, for their energy requirements. On the other hand, the protein expression differences in AAD6T and H. salina DSMZ 5928T showed that they prefer different metabolic pathways for lipid biosynthesis and in adaptation to extreme environments. Thus, we suggested that phylogenetic dissimilarities between these microorganisms could be related to the protein expression differences; in other words, metabolic flux differences in AAD6T and H. salina DSMZ 5928T. This is the first study to explain the dissimilarities of phenotypic characters and DNA-DNA hybridization between type strain and novel strain AAD6T by using protein expression differences.