Comparative proteome analysis of Brucella abortus 2308 and its virB type IV secretion system mutant reveals new T4SS-related candidate proteins

► We examine the expression of proteins in a virB mutant strain of Brucella abortus. ► 35% of proteins overexpressed in the mutant strain grown in acid medium are outer membrane and periplasmic proteins. ► Most of the proteins underexpressed in the virB mutant strain grown in acid medium are from cytoplasm. ► Acid medium affects mostly proteins in the external bacterial structures when virB is not functional. ► Some ofthe 69 analyzed proteins have not been described before in relation to a virB T4SS mutation.