The Role of Type IV Secretion System in Brucella Virulence: A Review

Brucellosis is a bacterial disease of domestic and wild animals caused by the genus Brucella which has great public health importance globally. In general, Brucella species do not express toxins or virulence factors that cause direct damage to the host. Instead, this pathogen’s strategy is to persist long enough in the infected host until transmission can occur, which in the natural hosts is usually through abortion, sexual contact, or shedding of bacteria in milk. One important Brucellavirulence factor for intracellular survival and persistence in the host is the type IV secretion system (T4SS).The type IV secretion system (T4SS) is one of numerous secretion systems used by microbes to transfer macromolecules through the cell membrane, such as proteins and DNA. It’s the most versatile secretion system, transporting monomeric proteins, multi-subunit protein poisons, and nucleoprotein complexes, and it’s found in Gram-positive and Gram-negative bacteria, as well as some Archaea. The type IV secretion system is a major Brucella virulence factor for intracellular survival and host persistence. This review will go through the present state of knowledge on the Brucella type IV secretion system, including its architecture and regulation, as well as the newly discovered effector substrates that this system delivers into host cells.