Genetic circuitry controlling motility behaviors of Myxococcus xanthus

Abstract

M. xanthus has a complex multicellular lifestyle including swarming, predation and development. These behaviors depend on the ability of the cells to achieve directed motility across solid surfaces. M. xanthus cells have evolved two motility systems including Type-IV pili that act as grappling hooks and a controversial engine involving mucus secretion and fixed focal adhesion sites. The necessity for cells to coordinate the motility systems and to respond rapidly to environmental cues is reflected by a complex genetic network involving at least three complete sets of chemosensory systems and eukaryotic-like signaling proteins. In this review, we discuss recent advances suggesting that motor synchronization results from spatial oscillations of motility proteins. We further propose that these dynamics are modulated by the action of multiple upstream complementary signaling systems. M. xanthus is thus an exciting emerging model system to study the intricate processes of directed cell migration.

A Bacterial Ras-Like Small GTP-Binding Protein and Its Cognate GAP Establish a Dynamic Spatial Polarity Axis to Control Directed Motility

“…For example, chemotaxis in liquid media relies on a temporal signal transduction cascade that switches the rotation of the flagellum [3]. However, one conspicuous example of dynamic cell polarization occurs during Myxococcus xanthus motility over solid surfaces (gliding motility): rod-shaped myxococcus cells control their direction of movement by inverting their polarity, rapidly switching their leading pole into their lagging cell pole (cellular reversal) [4]. Cellular reversals are highly regulated and mutants with impaired reversal frequencies cannot accomplish complex multicellular behaviors such as predation [5] and the capacity to develop fruiting bodies [6].…”

Single domain response regulators: molecular switches with emerging roles in cell organization and dynamics

“…M. xanthus cells lack flagella but are equipped with two distinct engines [31], eight Che-like chemosensory systems [32] and a record number of 42 SD-RRs [16]. Cell movement is powered by the extension and retraction of type IV pili (S-motility) and by the action of a gliding motor (A-motility) (summarized in: [33,34]). By virtue of the two engines, Myxococcus cells can move forward or backwards along their longitudinal axis.…”

“…This dynamic behavior is orchestrated by a small Ras-like GTPase, MglA, the only known protein to be essential for both S- and A-motility [39,40]. MglA acts as central recruitment factor for several key components of A- and S-motility engines and thus appears to direct cell reversal through spatial coordination of the two motility machineries [33]. …”

Motility Enhancement through Surface Modification Is Sufficient for Cyanobacterial Community Organization during Phototaxis

“…In natural environments, microbes live in communities that range from relatively simple to very complex in terms of species diversity [4]–[10], structure [11]–[13], and metabolic functions and pathways [14]–[16]. In complex communities, such as medically relevant biofilms [17], [18], swarms of social bacteria such as Myxococcus xanthus [19], [20], or microbial mats in the environment [4]–[6], community structure can be dynamic, involving the collective migration of cells in response to environmental cues [21], [22], and may depend on the production of an extracellular matrix, which can facilitate stabilization of spatial structure [23]–[27]. In the face of this complexity, mechanistic models of cellular interactions that recapitulate environmentally relevant community behaviors can enhance our understanding of structure-function relationships, particularly those that are at the interface of biological and physical phenomena.…”