About this Research Topic
For many years most microbiologists believed that bacteria inhabit the planet mainly as free-living cells. It is now widely recognized that most bacteria exist organized in multicellular communities, most frequently called biofilms. Biofilms are assemblages of cells adherent to each other and/or to a surface and embedded in a scaffold of self-produced extracellular polymeric substances (EPS). Under such conditions, cell-to-cell interactions lead to the establishment of dense, complex and highly structured populations.
Particularly challenging is to understand the complexity of intercellular interactions encountered in bacterial consortia, namely competitive or cooperative ones, together with their impact on the final outcome of these communities (e.g. differentiation, maturation, physiology, antimicrobial resistance, virulence, dispersal). Such interactions influence the temporal and spatial formation of a highly organized community architecture. Their significance was first realized and thoroughly described for bacteria growing as colonies on solid substrates and residing in the oral cavity. Equivalent patterns were later revealed in biofilm bacteria isolated from natural and artificial habitats, such as plants or food processing devices.
A relevant characteristic of these multicellular communities is the presence of different cell types, as observed in Bacillus subtilis colonies and biofilms, which reveal a cellular division of labor, a major feature of multicellular organisms. In addition, bacterial cells employ intercellular communication to coordinate multicellular activities and social behaviors. For instance, secreted signal molecules regulate the expression of quorum-sensing functions, such as bioluminescence, antibiotic production, sporulation, competence, or coordinated behaviors such as swarming motility, fruiting body formation, cannibalism, fratricide and extracellular DNA production. Thus, an individual cell can activate specific functions only by sensing its biological environment, including a critical population density or signals from a differentiated group of cells.
Bacteria in multicellular structures are more protected against various stresses than planktonic cells. Several studies have further suggested that interactions between bacterial aggregates could influence their relative resistance. Undoubtedly, bacterial multicellular structures should be envisioned as continuously evolving dynamic entities that cannot merely be seen as the sum of all components therein. It is now clear that the physiology and function of these complex microbial communities vary much from that of the individual species when examined as monocultures, and in some cases the specific molecular details are known.
This Research Topic aims to deliver deep insights into the mechanisms responsible for the development of multicellular bacterial populations (biofilms, colonies and swarms) and the tremendous impact multicellularity has on the function and physiology of these communities. As further insights into this complicated life style are made available, new targets to be exploited for antibacterial therapy will arise, giving us a much wider scope to control it efficiently. Evidently, we are just beginning to understand the complexity of bacterial multicellularity, but it is already clear that much is to be gained in doing so.
• Division of labor in bacterial populations
• Intercellular chemical communication
• Social or coordinated behaviors
• Physiological and molecular mechanisms involved in intra- and inter-species interactions
• Cooperative and competitive interactions within bacterial populations and their overall impact in the physiology and fitness of these communities
• Influence of environmental conditions and extracellular signals on the function and physiology of multicellular bacterial popul
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