Directed Binding of Gliding Bacterium, Mycoplasma mobile, Shown by Detachment Force and Bond Lifetime

mBio. 2016 Jun 28;7(3):e00455-16. doi: 10.1128/mBio.00455-16.

Abstract

Mycoplasma mobile, a fish-pathogenic bacterium, features a protrusion that enables it to glide smoothly on solid surfaces at a velocity of up to 4.5 µm s(-1) in the direction of the protrusion. M. mobile glides by a repeated catch-pull-release of sialylated oligosaccharides fixed on a solid surface by hundreds of 50-nm flexible "legs" sticking out from the protrusion. This gliding mechanism may be explained by a possible directed binding of each leg with sialylated oligosaccharides, by which the leg can be detached more easily forward than backward. In the present study, we used a polystyrene bead held by optical tweezers to detach a starved cell at rest from a glass surface coated with sialylated oligosaccharides and concluded that the detachment force forward is 1.6- to 1.8-fold less than that backward, which may be linked to a catch bond-like behavior of the cell. These results suggest that this directed binding has a critical role in the gliding mechanism.

Importance: Mycoplasma species are the smallest bacteria and are parasitic and occasionally commensal, as represented by Mycoplasma pneumoniae, which causes so-called "walking pneumonia" in humans. Dozens of species glide on host tissues, always in the direction of the characteristic cellular protrusion, by novel mechanisms. The fastest species, Mycoplasma mobile, catches, pulls, and releases sialylated oligosaccharides (SOs), which are common targets among influenza viruses, by means of a specific receptor based on the energy of ATP hydrolysis. Here, force measurements made with optical tweezers revealed that the force required to detach a cell from SOs is smaller forward than backward along the gliding direction. The directed binding should be a clue to elucidate this novel motility mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Fishes / microbiology
  • Glass / chemistry*
  • Locomotion
  • Mycoplasma / physiology*
  • Oligosaccharides / chemistry*
  • Oligosaccharides / physiology
  • Optical Tweezers
  • Polystyrenes / chemistry
  • Surface Properties

Substances

  • Bacterial Proteins
  • Oligosaccharides
  • Polystyrenes

Grant support

This work was supported by Grants-in-Aid for Scientific Research on Innovative Area, “Harmonized Supramolecular Motility Machinery and Its Diversity” no. 24117002 to M. Miyata and TN, no. 15H01329 to DN, “Fluctuation and Structure” no. 26103527 and 16H00808 to TN, “Cilia and Centrosomes” no. 15H01218 to TN, MEXT KAKENHI grants, and also by Grant-in-Aids for Scientific Research (A) no. 21249030 to M. Miyata, (B) no. 24390107 to M. Miyata and no. 15H04364 to TN, Grant-in-Aid for Young Scientists (A) no. 16H06230 to DN, MEXT KAKENHI.