[Biosocial phenomena in unicellular organisms (exemplified by data concerning Prokaryota)]

This review deals with the issue of applicability of biosocial concepts and terms to microorganisms. The main emphasis is placed on recent data obtained in studies of bacteria. They demonstrate various forms of collective behavior including affiliation (cohesion), cooperation, coordinated aggression, and avoidance behavior (vis-a-vis "outgroups"). Bacterial systems are also characterized by contact and distant communication; the latter mediated by chemical signals (including pheromones/autoinducers employed by quorum-sensing systems) or physical factors. Bacteria form supracellular systems (colonies, biofilms, flocs, etc.) that can be regarded as bacterial biosocial systems, by analogy to animal congregations. These bacterial biosocial systems are characterized by coherence, life-cycle ("culture ontogeny" in N.D. Yerusalimsky's usage), and hierarchical or network organization. Bacterial cells in biosocial systems are morphologically differentiated and, in a large number of bacterial species, functionally specialized. Cells collectively form structures that function as "organs" of the whole biosocial system (exemplified by water channels, colony-coating membranes, hemoprotein-containing hemosomes, and extracellular matrix as the structural basis of a colony/biofilm). The biosocial approach to microorganisms promotes interactions between microbiology, cytology, and ethology. It is also of practical value for medicine and biotechnology.