Infectious disease is the result of an intimate relationship between the pathogen and host, which involves cross-talk. After an initial flood of mainly descriptive reports on the influence of acute bacterial infection on cells, transcriptome and proteome studies are now becoming more refined in their approach, and are shedding light on the role of pathogen-specific mechanisms/structures in pathogenesis. In addition, studies of gene expression in vivo have shed new light on how the host influences the niche occupied by bacteria. Elegant refinements to proteomics using beads coated with bacterial invasins, or purifying subcellular fractions are producing a picture of invasion specific processes. Such approaches combined with modern functional genomics technologies such as RNAi represent the next phase in understanding host-bacteria interactions.