Book excerpt: Type IV secretion systems (T4SSs) are highly versatile membrane-associated transporter machines used by Gram-negative and Gram-positive bacteria to deliver substrate molecules to a large variety of target cells. This volume summarizes our current knowledge of the large variety and structural diversity of T4SSs in pathogenic Escherichia, Agrobacterium, Legionella, Coxiella, Bartonella, Helicobacter, Enterococcus and other species. Divided into 13 chapters contributed by leading experts, it presents findings that significantly enhance our understanding of how various pathogens manipulate host cell functions to trigger bacterial uptake, promote intracellular growth, suppress defense mechanisms and of how bacteria spread antibiotic resistances, thus facilitating bacterial colonization and disease development. The book is an invaluable source of information for researchers and clinicians.