IN SEARCH OF HIGHER ENERGY - METABOLISM-DEPENDENT BEHAVIOR IN BACTERIA

Bacteria use different strategies to navigate to niches where environm ental factors are favourable for growth, Chemotaxis is a behavioural r esponse mediated by specific receptors that sense the concentration of chemicals in the environment, Recently, a new type of sensor has been described in Escherichia coli that responds to changes in cellular en ergy (redox) levels. This sensor, Aer, guides the bacteria to environm ents that support maximal energy levels in the cells. A variety of sti muli, such as oxygen, alternative electron accepters, light, redox car riers that interact with the electron transport system and metabolized carbon sources, effect changes in the cellular energy (redox) levels, These changes are detected by Aer and by the serine chemotaxis recept or Tsr and are transduced into signals that elicit appropriate behavio ural responses, Diverse environmental signals from Aer and chemotaxis receptors converge and integrate at the level of the CheA histidine ki nase, Energy sensing is widespread in bacteria, and it is now evident that a variety of signal transduction strategies are used for the meta bolism-dependent behaviours. The occurrence of putative energy-sensing domains in proteins from cells ranging from Archaea to humans indicat es the importance of this function for all living systems.