Bacterial motility: links to the environment and a driving force for microbial physics

Abstract

Bacterial motility was recognized 300 years ago. Throughout this history, research into motility has led to advances in microbiology and physics. Thirty years ago, this union helped to make run and tumble chemotaxis the paradigm for bacterial movement. This review highlights how this paradigm has expanded and changed, and emphasizes the following points. The absolute magnitude of swimming speed is ecologically important because it helps determine vulnerability to Brownian motion, sensitivity to gradients, the type of receptors used and the cost of moving, with some bacteria moving at 1 mm s(-1). High costs for high speeds are offset by the benefit of resource translocation across submillimetre redox and other environmental gradients. Much of environmental chemotaxis appears adapted to respond to gradients of micrometres, rather than migrations of centimetres. In such gradients, control of ion pumps is particularly important. Motility, at least in the ocean, is highly intermittent and the speed is variable within a run. Subtleties in flagellar physics provide a variety of reorientation mechanisms. Finally, while careful physical analysis has contributed to our current understanding of bacterial movement, tactic bacteria are increasingly widely used as experimental and theoretical model systems in physics.

Polarity of bacterial magnetotaxis is controlled by aerotaxis through a common sensory pathway

“…As has been shown for other polarly flagellated bacteria 37,38 , M. gryphiswaldense does not tumble between smooth swimming phases, but instead swims in a typical run and reversal pattern, with speeds between 20 and 65 mm s À 1 , similar to previously reported values 12,13,39 . In equilibrium conditions, cells showed a reversal frequency of 0.126 s À 1 or less, which is low compared with data reported for non-MTB [40][41][42][43] .…”

You are what you talk: quorum sensing induces individual morphologies and cell division modes in Dinoroseobacter shibae

“…In D. shibae flagellar synthesis is controlled by AHL signaling. It has been calculated that marine bacteria may spend more than 10% of their total energy budget on movement, and the smaller the cell is, the larger is the amount of energy needed to stabilize it against Brownian movement (Mitchell, 2002;Mitchell and Kogure, 2006). Thus, the metabolic costs for flagellar synthesis are only worth spending in a diffusion-limited patchy microenvironment where motility might provide the chance to reach more optimal conditions or nutrients, a classical condition for QS.…”

Hydration dynamics promote bacterial coexistence on rough surfaces

“…Soil bacteria inhabit complex and heterogeneous pore spaces where water and nutrient resources essential for bacterial life may significantly vary across micrometeric spatial scales or entirely change within a single bacterial generation (Crawford et al, 2005;Mitchell and Kogure, 2006;Or et al, 2007;Banavar and Maritan, 2009). Hydration status and pore-space characteristics are critical factors shaping nutrient fields and bacterial motility, and are thus key to understanding bacterial interactions in soil and other porous media such as dry food products (Barton and Ford, 1997;Dens and Van Impe, 2000;Wilson et al, 2002;Chang and Halverson, 2003;Or et al, 2007;Chen and Jin, 2011).…”