Pushing the limits of cellular microbiology: microarrays to study bacteria-host cell intimate contacts.

Abstract

For more than a century, microbiologists studied pathogens in pure culture, whereas cell biologists studied mammalian cells in tissue culture. Both fields used rich media and conditions optimized for in vitro growth. A few years ago, researchers realized that these laboratory methods of growing pathogens and their hosts were quite artificial and had very little in common with real life, where pathogens and hosts coexist, interact, and compete in conditions that are often far from optimal. To better mimic what happens in real life, the study of the interaction between microbes and host cells was proposed, taking advantage of technological progress that allowed cocultures of microbes and cells to be handled together. A new discipline (cellular microbiology) was born (1). This discipline took over quite rapidly, a new journal named after this new discipline was started (Cellular Microbiology, Blackwell, Oxford), and textbooks were published (2, 3) describing in detail the techniques to be used in cellular microbiology and the scientific problems that could be addressed. These textbooks are just a few months old, when a powerful new approach to cellular microbiology is described (4). This novel approach pushes the limits that we had previously and suggests it is probably already time for a new edition of these textbooks. The new technique, reported in part by Belcher et al. in this issue of PNAS (4) and by other recent studies, describes how, instead of studying one parameter at a time, we can use microchips to study, within a single experiment, all of the host genes and those of the bacteria whose expression is modified during host–pathogen interaction: the global picture of the dialogue between the pathogen and the host in one experiment!