Seef, S. | bioRxiv Science

bioRxiv2021

A Tad-like apparatus is required for contact-dependent prey killing in predatory social bacteria

Myxococcus xanthus, a soil bacterium, predates collectively using motility to invade prey colonies. Prey lysis is mostly thought to rely on secreted factors, cocktails of antibiotics and enzymes, and direct contac with Myxococcus cells. In this study, we show that on surfaces the coupling of A-motility and contact-dependent killing is the central predatory mechanism driving effective prey colony invasion and consumption. At the molecular level, contact-dependent killing involves a newly discovered type IV filament-like machinery (Kil) that both promotes motility arrest and prey cell plasmolysis. In this process, Kil proteins assemble at the predator-prey contact site, suggesting that they allow tight contact with prey cells for their intoxication. Kil-like systems form a new class of Tad-like machineries in predatory bacteria, suggesting a conserved function in predator-prey interactions. This study further reveals a novel cell-cell interaction function for bacterial pili-like assemblages.

microbiology↗

bioRxiv2019

Establishing Rod-Shape from Spherical, Peptidoglycan-Deficient Bacterial Spores

Chemical-induced spores of the Gram-negative bacterium Myxococcus xanthus are peptidoglycan (PG)-deficient. It is unclear how these spherical spores germinate into rod-shaped, walled cells without preexisting PG templates. We found that germinating spores first synthesize PG randomly on spherical surfaces. MglB, a GTPase-activating protein, forms a cluster that surveys the status of PG growth and stabilizes at one future cell pole. Following MglB, the Ras family GTPase MglA localizes to the second pole. MglA directs molecular motors to transport the bacterial actin homolog MreB and the Rod PG synthesis complexes away from poles. The Rod system establishes rod-shape by elongating PG at nonpolar regions. Thus, the interaction between GTPase, cytoskeletons and molecular motors provides a mechanism for the de novo establishment of rod-shape in bacteria. SignificanceSpheres and rods are among the most common shapes adopted by walled bacteria, in which the peptidoglycan (PG) cell wall largely determines cell shape. When induced by chemicals, rod-shaped vegetative cells of the Gram-negative bacterium Myxococcus xanthus thoroughly degrade their PG and shrink into spherical spores. As these spores germinate, rod-shaped cells are rebuilt without preexisting templates, which provides a rare opportunity to visualize de novo PG synthesis and bacterial morphogenesis. In this study, we investigated how spherical spores germinate into rods and elucidated a system for rod-shape morphogenesis that includes the Rod PG synthesis system, a GTPase-GAP pair, the MreB cytoskeleton and a molecular motor.

microbiology↗