Proteome of the phytopathogen Xanthomonas citri subsp. citri: a global expression profile

In order to gain insight into the metabolism of Xac, cells were grown on two different media (NB - Nutrient Broth and TSE - Tryptone Sucrose broth enriched with glutamic acid), and proteins were proteolyzed with trypsin and examined by 2D LC-MS/MS. Approximately 39% of all predicted proteins by annotation of Xac were identified with their component peptides unambiguously assigned to tandem mass spectra. The proteins, about 1,100, were distributed in all annotated functional categories.This is the first proteomic reference map for the most aggressive strain of Xanthomonas pathogen of all orange varieties. The compilation of metabolic pathways involved with bacterial growth showed that Xac expresses a complete central and intermediary metabolism, replication, transcription and translation machineries and regulation factors, distinct membrane transporters (ABC, MFS and pumps) and receptors (MCP, TonB dependent and metabolites acquisition), two-component systems (sensor and regulatory components) and response regulators. These data corroborate the growth curve in vitro and are the first reports indicating that many of these genome annotated genes are translated into operative in Xac. This proteomic analysis also provided information regarding the influence of culture medium on growth and protein expression of Xac.Advances in genome sequencing have resulted in the description of a huge number of genes; some of these genes are hypothetical. However, the functions of many of these genes and the relationship among the many proteins that constitute the proteome of a cell or tissue cannot be easily determined. In addition, about half of the predicted proteins have no inferable functions, especially in microorganisms [1,2].Many approaches, such as two-hybrid systems and proteomics, have been used to describe genes that are effectively translated into proteins for systems of interest without considering transcriptomics or other methodologies that focus on RNA expression. Althou