Archaea on the move
Chemotaxis, the ability to sense and respond to environmental stimuli, allows microorganisms to navigate chemical and physical gradients in natural systems. Chemical stimuli that can be sensed by microorganisms include variations in pH and osmolarity as well as concentrations of toxins and oxygen, whereas physical stimuli sensed by microorganisms include the intensity and wavelength of light (Wadhams and Armitage, 2004). More recently, hydrogenotrophic microorganisms have been shown to be able to sense the concentration of hydrogen (Brileya et al., 2013). The ability to sense the environment is made possible by simple one-component (Ulrich etal., 2005) and more complex two-component signal transduction systems (Stock et al., 2000). A key difference between one- and two-component signal transduction systems is the location of the signals that are detected. One-component systems are thought to function primarily in detecting cytoplasmic signals, whereas two-component systems are thought to detect extracellular signals (Wuichet and Zhulin, 2010). One-component systems consist of a single protein that typically comprises a sensory and a regulatory domain, whereas two-component systems comprise two conserved proteins: a sensor and a response regulator.
Boyd, Eric S.. "Archaea on the move." Environmental Microbiology Reports 7, no. 3 (June 2015): 385-387. DOI:https://dx.doi.org/10.1111/1758-2229.12281.