Myxobacteria: Moving, Killing, Feeding, and Surviving Together

Abstract

Myxococcus xanthus, like other myxobacteria, is a social bacterium that moves and feeds cooperatively in predatory groups. On surfaces, rod-shaped vegetative cells move in search of the prey in a coordinated manner, forming dynamic multicellular groups referred to as swarms. Within the swarms, cells interact with one another and use two separate locomotion systems. Adventurous motility, which drives the movement of individual cells, is associated with the secretion of slime that forms trails at the leading edge of the swarms. It has been proposed that cellular traffic along these trails contributes to M. xanthus social behavior via stigmergic regulation. However, most of the cells travel in groups by using social motility, which is cell contact-dependent and requires a large number of individuals. Exopolysaccharides and the retraction of type IV pili at alternate poles of the cells are the engines associated with social motility. When the swarms encounter prey, the population of M. xanthus lyses and takes up nutrients from nearby cells. This cooperative and highly density-dependent feeding behavior has the advantage that the pool of hydrolytic enzymes and other secondary metabolites secreted by the entire group is shared by the community to optimize the use of the degradation products. This multicellular behavior is especially observed in the absence of nutrients. In this condition, M. xanthus swarms have the ability to organize the gliding movements of 1000s of rods, synchronizing rippling waves of oscillating cells, to form macroscopic fruiting bodies, with three subpopulations of cells showing division of labor. A small fraction of cells either develop into resistant myxospores or remain as peripheral rods, while the majority of cells die, probably to provide nutrients to allow aggregation and spore differentiation. Sporulation within multicellular fruiting bodies has the benefit of enabling survival in hostile environments, and increases germination and growth rates when cells encounter favorable conditions. Herein, we review how these social bacteria cooperate and review the main cell-cell signaling systems used for communication to maintain multicellularity.

PlpA, a PilZ‐like protein, regulates directed motility of the bacterium Myxococcus xanthus

“…For rod-shaped bacteria, cell poles constitute important regulatory platforms for a large number of cellular processes including division, differentiation, virulence, chemotaxis and both individual and collective movements (Treuner-Lange and Sogaard-Andersen, 2014;Schumacher and Sogaard-Andersen, 2017). The rod-shaped soil bacterium Myxococcus xanthus (M. xanthus) features directed motility, regulated pattern formation, biofilm formation and programmed differentiation into fruiting bodies (Muñoz-Dorado et al, 2016). All these functions require the moving direction of cells to be fine tuned in response to environmental and self-generated cues (Zusman et al, 2007;Schumacher and Sogaard-Andersen, 2017).…”

Understanding Microbial Divisions of Labor

“…Upon starvation, they undergo a dramatic transition where individual cells migrate together to create fruiting bodies containing ∼10 5 cells. Fruiting bodies in M. xanthus contain three differentiated cell types: spores, which comprise around 10% of the fruiting body, peripheral rods that comprise another 10–30%, and then the rest that die and lyse during development via a process assumed to be programmed cell death (PCD) (Shimkets, 1990; Claessen et al, 2014; Muñoz-Dorado et al, 2016). …”

Bacillus licheniformis escapes from Myxococcus xanthus predation by deactivating myxovirescin A through enzymatic glucosylation

“…Myxobacteria are a group of ubiquitous, soil-dwelling and gram-negative bacteria with complex social lives and multicellular developmental cycles, that is, surface motility, fruiting body formation, sporulation and especially predatory behaviour (Dawid, 2000;Muñoz-Dorado et al, 2016;Wrótniak-Drzewiecka et al, 2016). As natural predators of microorganisms, myxobacteria are one of the most common and diverse groups of bacteria that exhibit a broad prey range of both soil bacteria and clinically important pathogens, suggesting that they have significant ecological and evolutionary impacts on their prey (Morgan et al, 2010;Findlay, 2016;Livingstone et al, 2017).…”