Microbe-host signalling is now a well accepted concept and an intensively studied research field. Although some of the observed bacterial phenotypes are attributed to host-recognition and inter-kingdom signalling, most of them are not relying on a proved molecular mechanism. Recent progress revealed some recognition and signalling pathways for host molecules in bacterial cells, which try to explain their modulatory effect on growth and virulence. Since the current knowledge on the field is poor and debatable, the purpose of this paper is to review and discuss the research performed in order to elucidate the ways by which microbial cells recognize and decode the host molecule signals.