In light of recent data, microorganisms are construed in the present monograph as living organisms that are capable of communication and advanced social organization, which conspicuously manifests itself in the formation of extracellular matrix-enclosed biofilms. Microbial communication signals, including quorum sensing pheromones, are of paramount importance both for interactions among microbial cells and the dialogue between them and the host organism. The monograph sums up the facts that demonstrate the complexity of the human organism-inhabiting microbial consortium comprising a wide...