Signal Transduction in Microorganisms
In addition to the flow of metabolites and energy that drives the distribution of populations of a wide variety of micro-organisms. These cells respond to specific signals from their environment and from other organisms. The responses allow them to adapt to changing conditions and to generate stable ecological interactions. The stimuli vary enormously and include changes in light, temperature, osmolality, nutrient availability and changes in the presence of adherable surfaces. The organisms generally respond to these changes by modulating their metabolic potential and gene expression. They have mechanisms that allow them to sense the density of members of their own species or in the case of parasites and symbionts of appropriate host organisms. They can adapt by inducing the expression of previously repressed genes and gaining new catalytic capacity, eg the adaptation to anaerobiosis and nitrate utilization (Stewart et al., 1989). In addition, micro-organisms can undergo extensive morphological and physiological change, eg sporulation or lateral flagella formation and they can modify their own environment, for example, by growing in microbial mats to allow for efficient nutrient utilization. How do micro-organisms detect environmental change? How do they integrate environmental information to generate an appropriate response? And how do these mechanisms evolve so that they can be adapted to the ecological strategy of specific organisms?