Phage-Phage, Phage-Bacteria, and Phage-Environment Communication

Abstract

Besides obtaining and utilizing resources, organisms have three basic ecological tasks: to survive, to reproduce, and to move. Survival is necessary for reproduction, reproduction increases numbers, and movement at a minimum assures that all of an organism’s ‘eggs’ are not found in the same spatial ‘basket’. For bacteriophages (phages), these facets can be differentiated into mechanisms that operate within the context of bacterial hosts (intracellularly) versus less so, i.e., instead extracellularly. Survival of phages, or their inactivation, thus can occur in the course of infection of bacteria, or instead as free virions, that is, as phages which have not yet adsorbed and infected a bacterium. Reproduction by phages can range from that which is more closely linked with normal bacterial metabolism and which ends with the phage intracellular (as in the course of lysogenic cycles) to that which involves substantial modification of normal bacterial metabolism and which ends with the phage now extracelullar (as in the course of lytic cycles). Movement of phages can occur most familiarly as diffusing virions, but also while phages are infecting bacteria. In the course of undergoing these and other processes, materials and information can flow from one entity to another, such as resulting in, for example, detection by infecting phages of multiple virion adsorptions to the same cell, transfer of genetic material from phages to bacteria, or extracellular factors influencing phage infection abilities. Broadly, such flow of materials and information from one entity to another can be described as different processes of communication, including between phages, between phages and bacteria, or between phages and the environment more generally. In this chapter I explore such phage-associated communication including, particularly, in terms of its impact on phage ecology.