Emergence of Escherichia coli critically buckled motile helices under stress

Abstract

Bacteria under external stress can reveal unexpected emergent phenotypes. We show that the intensely studied bacterium Escherichia coli can transform into long, highly motile helical filaments poized at a torsional buckling criticality when exposed to minimum inhibitory concentrations of several antibiotics. While the highly motile helices are physically either right- or left-handed, the motile helices always rotate with a right-handed angular velocity ω→, which points in the same direction as the translational velocity v→T of the helix. Furthermore, these helical cells do not swim by a “run and tumble” but rather synchronously flip their spin ω→ and thus translational velocity—backing up rather than tumbling. By increasing the translational persistence length, these dynamics give rise to an effective diffusion coefficient up to 20 times that of a normal E. coli cell. Finally, we propose an evolutionary mechanism for this phenotype’s emergence whereby the increased effective diffusivity provides a fitness advantage in allowing filamentous cells to more readily escape regions of high external stress.

Modeling metabolic networks of individual bacterial agents in heterogeneous and dynamic soil habitats (IndiMeSH)

“…When entering a pore where the cell would be immobile due to thin water films, the cell has a 10% chance at each time step to detach back into the previous node. Mounting evidence suggests that motile cells can extract themselves from tight spots [35] but information is insufficient to quantify the efficiency of such processes. We thus have assigned a small probability to account for the occurrence of such relatively rare events.…”

Molecular and morphological clocks for estimating evolutionary divergence times

“…Second, a dataset of 353 discrete morphological characters and 5096 molecular characters (bp) from 55 Hymenoptera species was taken from Ronquist et al (2012) [ 10 ]. Third, a dataset of 121 discrete morphological characters and 19,870 molecular characters (bp) from 18 Spermatophyta species was obtained from Doyle (2006) [ 36 ] and Morris et al (2018) [ 37 ], respectively. Three rooted trees (Fig.…”

“…Three rooted trees (Fig. 8 ) were constructed based on the literature: one for Hemiptera species [ 32 ], one for Hymenoptera species [ 10 ], and one for Spermatophyta species [ 37 ]. The three topologies from Fig.…”

“…8 were fixed in all analyses to ensure consistent calibrations and avoid the confounding effects of alternative phylogenies and calibrations. Moreover, the use of a phylogeny reliably inferred as a fixed topology for dating is a common practice (e.g., [ 7 , 37 – 40 ]).…”

Correlative Microscopy: a tool for understanding soil weathering in modern analogues of early terrestrial biospheres

“…Colonization of the land by plants and other organisms during the early Palaeozoic (~ 500 Ma 1 ) was fundamental to the evolution of terrestrial landscapes. The expansion of primordial vegetation had an influential effect on the architecture and evolution of river and sedimentary systems 2 , 3 , weathering and soil development 4 – 6 , and crucially the drawdown of atmospheric CO 2 through organic carbon burial and weathering 7 , 8 .…”