Insights into the Gene Expression Profile of Uncultivable Hemotrophic Mycoplasma suis during Acute Infection, Obtained Using Proteome Analysis

Hemotrophic mycoplasmas, bacteria without cell walls whose niche is the erythrocytes of their hosts, have never been cultivated in vitro. Therefore, knowledge of their pathogenesis is fundamental.Mycoplasma suis infects pigs, causing either acute fatal he-molytic anemia or chronic low-grade anemia, growth retardation, and immune suppression. Recently, the complete genomes of two hemotrophic mycoplasma species,M. suis andM. haemofelis, were sequenced, offering new strategies for the analysis of their pathogenesis. In this study we implemented a proteomic approach to identifyM. suis proteins during acute infection by using tandemmass spectrometry. Twenty-two percent of the predicted proteins encoded inM. suis strain KI_3806 were identi-fied. These included nearly all encoded proteins of glycolysis and nucleotide metabolism. The proteins for lipid metabolism, however, were underrepresented. A high proportion of the detected proteins are involved in information storage and processing (72.6%). In addition, several proteins of different functionalities, i.e., posttranslational modification, membrane genesis, signal transduction, intracellular trafficking, inorganic ion transport, and defense mechanisms, were identified. In its reduced genome, M. suis harbors 65.3 % (strain Illinois) and 65.9 % (strain KI_3806) of the genes encode hypothetical proteins. Of these, only 6.3% were identified at the proteome level. All proteins identified in this study are present in bothM. suis strains and are encoded i