Questioning rotary functionality in the bacterial flagellar system and proposing a murburn model for motility

Abstract

Bacterial flagellar system (BFS) was the primary example of a purported ‘rotary-motor’ functionality in a natural assembly. This mandates the translation of a circular motion of components inside into a linear displacement of the cell body outside, which is supposedly orchestrated with the following features of the BFS: (i) A chemical/electrical differential generates proton motive force (pmf, including a trans-membrane potential, TMP), which is electro-mechanically transduced by inward movement of protons via BFS. (ii) Membrane-bound proteins of BFS serve as stators and the slender filament acts as an external propeller, culminating into a hook-rod that pierces the membrane to connect to a ‘broader assembly of deterministically movable rotor’. We had disclaimed the purported pmf/TMP-based respiratory/photosynthetic physiology involving Complex V, which was also perceived as a ‘rotary machine’ earlier. We pointed out that the murburn redox logic was operative therein. We pursue the following similar perspectives in BFS-context: (i) Low probability for the evolutionary attainment of an ordered/synchronized teaming of about two dozen types of proteins (assembled across five-seven distinct phases) towards the singular agendum of rotary motility. (ii) Vital redox activity (not the gambit of pmf/TMP!) powers the molecular and macroscopic activities of cells, including flagella. (iii) Flagellar movement is noted even in ambiances lacking/countering the directionality mandates sought by pmf/TMP. (iv) Structural features of BFS lack component(s) capable of harnessing/achieving pmf/TMP and functional rotation. A viable murburn model for conversion of molecular/biochemical activity into macroscopic/mechanical outcomes is proposed herein for understanding BFS-assisted motility.

HIGHLIGHTS

• The motor-like functionalism of bacterial flagellar system (BFS) is analyzed

• Proton/Ion-differential based powering of BFS is unviable in bacteria

• Uncouplers-sponsored effects were misinterpreted, resulting in a detour in BFS research

• These findings mandate new explanation for nano-bio-mechanical movements in BFS

• A minimalist murburn model for the bacterial flagella-aided movement is proposed

Communicated by Ramaswamy H. Sarma

Keywords:

• Bacterial flagella
• murburn concept
• ion-fluxes
• proton motive force (pmf)
• rotation

Acknowledgments

The work was powered by Satyamjayatu: The Science & Ethics Foundation.

Author contributions

KMM identified crucial shortcomings of the classical explanation and prepped the first draft of the paper (including the images), also proposing the murburn alternatives. VS helped in writing the paper with contents in various sections, shared critical inputs, important literature and experience gained from hands-on working in the BFAM field for several years on his doctoral thesis at IIT Delhi. VDJ helped with discussions and crucial videos/literature. MK & HT verified the computations/concepts in mechanical/energetics/fluid dynamics aspects and provided crucial inputs. LJ discussed various aspects of the write-up, suggested points regarding order-disordering water structures and critically enhanced the manuscript’s presentation.

Dedication

This article is dedicated to all those scientists that dared to question Mitchell and Boyer’s untenable proposals; and also to those scientists that disengage with inertial mindset, jettison obsolete ideas and adopt more sensible solutions.

Disclosure statement

No potential conflict of interest was reported by the author(s)

Ethics statement

This article preparation did not involve experimentation with any living systems and the article was prepared along the guidelines provided for authors.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.