Faculty Opinions recommendation of Circular swimming motility and disordered hyperuniform state in an algae system.

Abstract Vorticella convallaria is a ciliated protozoan found in freshwater habitats. In the sessile or stalked trophont form, V. convallaria is shaped somewhat like a balloon as it has a body or zooid (the head of the balloon) that is about 40 μm large with cilia around its oral part, and a stalk (the string of a balloon) anchoring the zooid to a solid surface. When a trophont zooid of V. convallaria detached from the stalk, the zooid swims around in water by creating water flow using its oral cilia. In contrast to the stalk contraction of V. convallaria that has been well studied, the swimming motility of V. convallaria is little known. In this study, we measured the swimming trajectories of the stalkless trophont zooid of V. convallaria using video microscopy and Hele-Shaw cells with a gap height of 25 μm, traced the swimming zooid using image processing, and analyzed the swimming motion in terms of swimming velocity and mean square displacement. The stalkless trophont zooid of V . convallaria was found to swim in circular patterns with intermittent ballistic motions in the confinement, and the average swimming speed ranged from 20 μm/s to 110 μm/s. Since the swimming pattern of V. convallaria appeared to be affected by the level of confinement, we will continue characterizing the ciliate’s swimming in the Hele-Shaw cell with different gap heights. Our study is expected to reveal the swimming motility of V. convallaria and to advance general understanding of swimming of microorganisms.

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Pressure-Ineduced Activation of the Swimming Motility of Magnetotactic Bacterium

Biophysical Journal ◽

10.1016/j.bpj.2017.11.1820 ◽

2018 ◽

Vol 114 (3) ◽

pp. 324a

Author(s):

Masayoshi Nishiyama ◽

Ruan Juanfang ◽

Takayuki Kato ◽

Toru Minamino ◽

Keiichi Namba ◽

...

Keyword(s):

Magnetotactic Bacterium ◽

Swimming Motility

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Evolutionary Plasticity of AmrZ Regulation in Pseudomonas

mSphere ◽

10.1128/msphere.00132-18 ◽

2018 ◽

Vol 3 (2) ◽

pp. e00132-18 ◽

Cited By ~ 4

Author(s):

David A. Baltrus ◽

Kevin Dougherty ◽

Beatriz Diaz ◽

Rachel Murillo

Keyword(s):

Pseudomonas Syringae ◽

Negative Regulator ◽

Regulatory Function ◽

Dual Function ◽

Genomic Context ◽

Master Regulator ◽

Content Type ◽

Swimming Motility ◽

Positive Regulator ◽

Mode Of Regulation

ABSTRACT amrZ encodes a master regulator protein conserved across pseudomonads, which can be either a positive or negative regulator of swimming motility depending on the species examined. To better understand plasticity in the regulatory function of AmrZ, we characterized the mode of regulation for this protein for two different motility-related phenotypes in Pseudomonas stutzeri. As in Pseudomonas syringae, AmrZ functions as a positive regulator of swimming motility within P. stutzeri, which suggests that the functions of this protein with regard to swimming motility have switched at least twice across pseudomonads. Shifts in mode of regulation cannot be explained by changes in AmrZ sequence alone. We further show that AmrZ acts as a positive regulator of colony spreading within this strain and that this regulation is at least partially independent of swimming motility. Closer investigation of mechanistic shifts in dual-function regulators like AmrZ could provide unique insights into how transcriptional pathways are rewired between closely related species. IMPORTANCE Microbes often display finely tuned patterns of gene regulation across different environments, with major regulatory changes controlled by a small group of “master” regulators within each cell. AmrZ is a master regulator of gene expression across pseudomonads and can be either a positive or negative regulator for a variety of pathways depending on the strain and genomic context. Here, we demonstrate that the phenotypic outcomes of regulation of swimming motility by AmrZ have switched at least twice independently in pseudomonads, so that AmrZ promotes increased swimming motility in P. stutzeri and P. syringae but represses this phenotype in Pseudomonas fluorescens and Pseudomonas aeruginosa. Since examples of switches in regulatory mode are relatively rare, further investigation into the mechanisms underlying shifts in regulator function for AmrZ could provide unique insights into the evolution of bacterial regulatory proteins.

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