Force and Stepwise Movements of Gliding Motility in Human Pathogenic Bacterium Mycoplasma pneumoniae.

Masaki Mizutani,Makoto Miyata,Yuya Sasajima

doi:10.3389/fmicb.2021.747905

Abstract

Mycoplasma pneumoniae, a human pathogenic bacterium, binds to sialylated oligosaccharides and glides on host cell surfaces via a unique mechanism. Gliding motility is essential for initiating the infectious process. In the present study, we measured the stall force of an M. pneumoniae cell carrying a bead that was manipulated using optical tweezers on two strains. The stall forces of M129 and FH strains were averaged to be 23.7 and 19.7 pN, respectively, much weaker than those of other bacterial surface motilities. The binding activity and gliding speed of the M129 strain on sialylated oligosaccharides were eight and two times higher than those of the FH strain, respectively, showing that binding activity is not linked to gliding force. Gliding speed decreased when cell binding was reduced by addition of free sialylated oligosaccharides, indicating the existence of a drag force during gliding. We detected stepwise movements, likely caused by a single leg under 0.2-0.3 mM free sialylated oligosaccharides. A step size of 14-19 nm showed that 25-35 propulsion steps per second are required to achieve the usual gliding speed. The step size was reduced to less than half with the load applied using optical tweezers, showing that a 2.5 pN force from a cell is exerted on a leg. The work performed in this step was 16-30% of the free energy of the hydrolysis of ATP molecules, suggesting that this step is linked to the elementary process of M. pneumoniae gliding. We discuss a model to explain the gliding mechanism, based on the information currently available.

Highlights

Members of the bacterial class Mollicutes, which includes the genus Mycoplasma, are parasitic and occasionally commensal bacteria that are characterized by small cells and genomes and by the absence of a peptidoglycan layer (Razin et al, 1998; Razin and Hayflick, 2010)
M. pneumoniae cells bind to human epithelial surfaces through sialylated oligosaccharides (SOs), which are major structures of animal cell surfaces related to cell-cell recognition, and the binding targets of many pathogens and toxins (Nagai and Miyata, 2006; Varki, 2008; Kasai et al, 2013; Williams et al, 2018)
Mainly we focused on a type strain “M129B7,” and another major strain called “FH.” The FH strain used in this study has not been genomically analyzed

Summary

INTRODUCTION

Members of the bacterial class Mollicutes, which includes the genus Mycoplasma, are parasitic and occasionally commensal bacteria that are characterized by small cells and genomes and by the absence of a peptidoglycan layer (Razin et al, 1998; Razin and Hayflick, 2010). The internal core comprises three parts: a terminal button, paired plates, and a bowl complex from the front side of the cell (Figure 1B; Nakane et al, 2015; Kawamoto et al, 2016; Miyata and Hamaguchi, 2016a). The major surface structure, called “P1 adhesin complex” or “genitalium and pneumoniae cytoadhesin (GPCA),” is composed of P1 adhesin and P40/P90 proteins and aligned around the internal structure, which plays a dual role as the adhesin to bind to SOs and as the leg for gliding (Figure 1B; Nakane et al, 2011; Aparicio et al, 2018, 2020; Vizarraga et al, 2020, 2021). We succeeded in detecting and measuring stepwise movements that are likely linked to the elementary process of the gliding reaction

MATERIALS AND METHODS

RESULTS

DISCUSSION