Bacterial energy taxis: a global strategy?

Abstract

A functional energy metabolism is one of the most important requirements for survival of all kinds of organisms including bacteria. Therefore, many bacteria actively seek conditions of optimal metabolic activity, a behaviour which can be termed "energy taxis". Motility, combined with the sensory perception of the internal energetic conditions, is prerequisite for tactic responses to different energy levels and metabolic yields. Diverse mechanisms of energy sensing and tactic response have evolved among various bacteria. Many of the known energy taxis sensors group among the methyl-accepting chemotaxis protein (MCP)-like sensors. This review summarizes recent advances in the field of energy taxis and explores the current concept that energy taxis is an important part of the bacterial behavioural repertoire in order to navigate towards more favourable metabolic niches and to survive in a specific habitat.

Fig. 1

Schematic overview of representative examples for different proposed bacterial energy taxis sensors and energy-related taxis sensors. In general, stimuli are sensed by MCP receptor dimers that can be associated in receptor clusters. Signals from MCPs are transduced via the chemotaxis core components CheA and CheY to the motility apparatus (this can be flagella or non-flagellar motility systems such as pili or gliding motility). Proposed stimuli or sensing mechanisms are depicted together with the model of each sensor type. NDH-1 NADH dehydrogenase I, Q quinone pool, ROS reactive oxygen species. For other abbreviations and specific sensor names, see text