Assessment of a Weak Mode of Bacterial Adhesion by Applying an Electric Field

Microbial attachment to surfaces is ubiquitous in nature. Most species of bacteria attach and adhere to surfaces via special appendages such as pili and fimbriae, the roles of which have been extensively studied. Here, we report an experiment on pilus-less mutants of Caulobacter crescentus weakly attached to polyethylene surface. We find that some individual cells transiently but repeatedly adhere to the surface in a stick-slip fashion in the presence of an electric field parallel to the surface. These bacteria move significantly slower than the unattached ones in the same field of view undergoing electrophoretic motion. We refer this behavior of repeated and transient attachment as “quasi-attachment”. The speed of the quasi-attached bacteria exhibits large variation, frequently dropping close to zero for short intervals of time. We propose a polymeric tethering model to account for the experimental findings. This study sheds light on bacteria–surface interaction, which is significant in broader contexts such as infection and environmental control.

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Assessment of a weak mode of bacterial adhesion by applying an electric field

10.1101/2020.04.01.020255 ◽

2020 ◽

Author(s):

George Araujo ◽

Joy Zheng ◽

Jae Jong Oh ◽

Jay X. Tang

Keyword(s):

Electric Field ◽

Environmental Control ◽

Caulobacter Crescentus ◽

Surface Interaction ◽

Bacterial Attachment ◽

Stick Slip ◽

Attached Bacteria ◽

Plastic Surface ◽

Unique Approach ◽

Microbial Attachment

ABSTRACTMicrobial attachment to surfaces is ubiquitous in nature. Most species of bacteria attach and adhere to surfaces via special appendages such as pili and fimbriae, the roles of which have been extensively studied. Here we report an experiment on pilus-less mutants of Caulobacter crescentus weakly attached to a plastic surface and subjected to an electric field parallel to the surface. We find that some individual cells transiently but repeatedly adhere to the surface in a stick-slip fashion in the presence of an electric field. Even while transiently detached, these bacteria move significantly slower than the unattached ones in the same field of view undergoing electrophoretic motion. We refer this behavior of repeated and transient attachment as “quasi-attachment”. The speed of the quasi-attached bacteria exhibits large variations, frequently dropping close to zero for short intervals of time. This study suggests applying electric field as a useful method to investigate bacteria-surface interaction, which is significant in broader contexts such as infection and environmental control.SignificanceInteraction between bacteria and surfaces occur widely in nature, including those in industrial, environmental, and medical settings. It is therefore important to understand various mechanisms and factors that affect numerous forms of bacterium-surface interaction, particularly those resulting in adhesion or attachment, be they strong or weak, permanent or transient. This work takes a unique approach to identify a transient and reversible mode of bacterial attachment to a solid surface, by applying an electric field to exert a force for detachment. The force thus exerted proves to reach the amplitude required to detach bacteria of a pilus-less strain that weakly attach to a plastic surface. The method may be applied broadly to investigate bacteria-surface interaction.

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Impending Collision Judgment from an Egocentric Perspective in Real and Virtual Environments: A Review

Perception ◽

10.1177/0301006619861892 ◽

2019 ◽

Vol 48 (9) ◽

pp. 769-795 ◽

Cited By ~ 4

Author(s):

Ilja T. Feldstein

Keyword(s):

Virtual Environments ◽

Observation Time ◽

Field Of View ◽

Spatial Distance ◽

Driving Experience ◽

Factors Affecting ◽

The Past ◽

Technical Factors ◽

Potential Factors ◽

Experimental Findings

The human egocentric perception of approaching objects and the related perceptual processes have been of interest to researchers for several decades. This article gives a literature review on numerous studies that investigated the phenomenon when an object approaches an observer (or the other way around) with the goal to single out factors that influence the perceptual process. A taxonomy of metrics is followed by a breakdown of different experimental measurement methods. Thereinafter, potential factors affecting the judgment of approaching objects are compiled and debated while divided into human factors (e.g., gender, age, and driving experience), compositional factors (e.g., approaching velocity, spatial distance, and observation time), and technical factors (e.g., field of view, stereoscopy, and display contrast). Experimental findings are collated, juxtaposed, and critically discussed. With virtual-reality devices having taken a tremendous developmental leap forward in the past few years, they have been able to gain ground in experimental research. Therefore, special attention in this article is also given to the perception of approaching objects in virtual environments and put in contrast to the perception in reality.

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Fluorescence-Based Bacterial Overlay Method for Simultaneous In Situ Quantification of Surface-Attached Bacteria

Applied and Environmental Microbiology ◽

10.1128/aem.02884-06 ◽

2007 ◽

Vol 73 (8) ◽

pp. 2653-2660 ◽

Cited By ~ 24

Author(s):

Rainer Müller ◽

Gerhard Gröger ◽

Karl-Anton Hiller ◽

Gottfried Schmalz ◽

Stefan Ruhl

Keyword(s):

Surface Chemistry ◽

Bacterial Adhesion ◽

Bacterial Attachment ◽

Bacterial Adherence ◽

Model Organisms ◽

Adhesion Properties ◽

Attached Bacteria ◽

Overlay Method ◽

Biomaterial Surfaces

ABSTRACT For quantification of bacterial adherence to biomaterial surfaces or to other surfaces prone to biofouling, there is a need for methods that allow a comparative analysis of small material specimens. A new method for quantification of surface-attached biotinylated bacteria was established by in situ detection with fluorescence-labeled avidin-D. This method was evaluated utilizing a silicon wafer model system to monitor the influences of surface wettability and roughness on bacterial adhesion. Furthermore, the effects of protein preadsorption from serum, saliva, human serum albumin, and fibronectin were investigated. Streptococcus gordonii, Streptococcus mitis, and Staphylococcus aureus were chosen as model organisms because of their differing adhesion properties and their clinical relevance. To verify the results obtained by this new technique, scanning electron microscopy and agar replica plating were employed. Oxidized and poly(ethylene glycol)-modified silicon wafers were found to be more resistant to bacterial adhesion than wafers coated with hydrocarbon and fluorocarbon moieties. Roughening of the chemically modified surfaces resulted in an overall increase in bacterial attachment. Preadsorption of proteins affected bacterial adherence but did not fully abolish the influence of the original surface chemistry. However, in certain instances, mostly with saliva or serum, masking of the underlying surface chemistry became evident. The new bacterial overlay method allowed a reliable quantification of surface-attached bacteria and could hence be employed for measuring bacterial adherence on material specimens in a variety of applications.

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Self-Consistent Supercell Band-Structure Calculations for the Investigation of the Electric Field Gradient at Impurity Sites in Cd Metal

Zeitschrift für Naturforschung A ◽

10.1515/zna-1987-1116 ◽

1987 ◽

Vol 42 (11) ◽

pp. 1321-1326 ◽

Cited By ~ 9

Author(s):

P. C. Schmidt ◽

Al. Weiss ◽

S. Cabus ◽

J. Küber

Keyword(s):

Band Structure ◽

Electric Field ◽

Electric Field Gradient ◽

Field Gradient ◽

Band Structure Calculations ◽

Densities Of States ◽

Experimental Findings ◽

Impurity Sites ◽

Structure Calculations ◽

Theoretical Results

The electric field gradient (EFG) at the nuclei of the 5 sp impurities In, Sn, Sb, I and Xe in Cd metal is investigated on the basis of supercell band structure calculations of Cd15M(M = In , . . . , Xe). The theoretical results show the same trend as the experimental findings. The differences in the EFG for different impurities are related to the charge distribution and partial densities of states.

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A polysaccharide deacetylase enhances bacterial adhesion in high ionic strength environments

10.1101/2021.04.16.440180 ◽

2021 ◽

Author(s):

Nelson K Chepkwony ◽

Yves V Brun

Keyword(s):

Ionic Strength ◽

Bacterial Adhesion ◽

Caulobacter Crescentus ◽

High Ionic Strength ◽

Aquatic Environments ◽

Binding Properties ◽

Surface Attachment ◽

Physico Chemical ◽

Temperature Shear ◽

Chemical Conditions

The adhesion of organisms to surfaces in aquatic environments provides a diversity of benefits such as better access to nutrients or protection from the elements or from predation. Differences in ionic strength, pH, temperature, shear forces, and other environmental factors impact adhesion and organisms have evolved various strategies to optimize their adhesins for their specific environmental conditions. We know essentially nothing about how bacteria evolved their adhesive mechanisms to attach efficiently in environments with different physico-chemical conditions. Many species of Alphaproteobacteria, including members of the order Caulobacterales, use a polar adhesin, called holdfast, for surface attachment and subsequent biofilm formation in both freshwater and marine environments. Hirschia baltica, a marine member of Caulobacterales, produces a holdfast adhesin that tolerates a drastically higher ionic strength than the holdfast produced by its freshwater relative, Caulobacter crescentus. In this work, we show that the holdfast polysaccharide deacetylase HfsH plays an important role in adherence in high ionic strength environments. We show that deletion of hfsH in H. baltica disrupts holdfast binding properties and structure. Increasing expression of HfsH in C. crescentus improved holdfast binding in high salinity, whereas lowering HfsH expression in H. baltica reduced holdfast binding at high ionic strength. We conclude that HfsH plays a role in modulating holdfast binding at high ionic strength and hypothesize that this modulation occurs through varied deacetylation of holdfast polysaccharides.

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Comparative analysis of ionic strength tolerance between freshwater and marine Caulobacterales adhesins

10.1101/523142 ◽

2019 ◽

Author(s):

Nelson K. Chepkwony ◽

Cécile Berne ◽

Yves V. Brun

Keyword(s):

Comparative Analysis ◽

Chemical Composition ◽

Ionic Strength ◽

Physicochemical Properties ◽

Bacterial Adhesion ◽

Marine Bacterium ◽

Caulobacter Crescentus ◽

High Ionic Strength ◽

Shear Forces ◽

Surface Attachment

ABSTRACTBacterial adhesion is affected by environmental factors, such as ionic strength, pH, temperature, and shear forces, and therefore marine bacteria must have developed holdfasts with different composition and structures than their freshwater counterparts to adapt to their natural environment. The dimorphic α-proteobacterium Hirschia baltica is a marine budding bacterium in the Caulobacterales clade. H. baltica uses a polar adhesin, the holdfast, located at the cell pole opposite the reproductive stalk for surface attachment and cell-cell adhesion. The holdfast adhesin has been best characterized in Caulobacter crescentus, a freshwater member of the Caulobacterales, and little is known about holdfast composition and properties in marine Caulobacterales. Here we use H. baltica as a model to characterize holdfast properties in marine Caulobacterales. We show that freshwater and marine Caulobacterales use similar genes in holdfast biogenesis and that these genes are highly conserved among the two genera. We also determine that H. baltica produces larger holdfast than C. crescentus and that those holdfasts have a different chemical composition, as they contain N-acetylglucosamine and galactose monosaccharide residues and proteins, but lack DNA. Finally, we show that H. baltica holdfasts tolerate higher ionic strength than those of C. crescentus. We conclude that marine Caulobacterales holdfasts have physicochemical properties that maximize binding in high ionic strength environments.IMPORTANCEMost bacteria spend a large amount of their lifespan attached to surfaces, forming complex multicellular communities called biofilms. Bacteria can colonize virtually any surface, therefore they have adapted to bind efficiently in very different environments. In this study, we compare the adhesive holdfasts produced by the freshwater bacterium C. crescentus and a relative, the marine bacterium H. baltica. We show that H. baltica holdfasts have a different morphology and chemical composition, and tolerate high ionic strength. Our results show that H. baltica holdfast is an excellent model to study the effect of ionic strength on adhesion and providing insights on the physicochemical properties required for adhesion in the marine environment.

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Exploring ultrafast threshold switching in In3SbTe2 phase change memory devices

Scientific Reports ◽

10.1038/s41598-019-55874-5 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Nishant Saxena ◽

Christoph Persch ◽

Matthias Wuttig ◽

Anbarasu Manivannan

Keyword(s):

Thermal Stability ◽

Electric Field ◽

Phase Change ◽

High Speed ◽

Phase Change Materials ◽

Phase Change Memory ◽

Threshold Switching ◽

Experimental Findings ◽

Thermal Stability Of ◽

Change Memory

AbstractPhase change memory (PCM) offers remarkable features such as high-speed and non-volatility for universal memory. Yet, simultaneously achieving better thermal stability and fast switching remains a key challenge. Thus, exploring novel materials with improved characteristics is of utmost importance. We report here, a unique property-portfolio of high thermal stability and picosecond threshold switching characteristics in In3SbTe2 (IST) PCM devices. Our experimental findings reveal an improved thermal stability of amorphous IST compared to most other phase change materials. Furthermore, voltage dependent threshold switching and current-voltage characteristics corroborate an extremely fast, yet low electric field threshold switching operation within an exceptionally small delay time of less than 50 picoseconds. The combination of low electric field and high speed switching with improved thermal stability of IST makes the material attractive for next-generation high-speed, non-volatile memory applications.

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The effects of thunderstorms and lightning discharges on the Earth's electric field

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1939.0009 ◽

1939 ◽

Vol 238 (791) ◽

pp. 249-303 ◽

Cited By ~ 46

Keyword(s):

Electric Field ◽

High Speed ◽

Potential Gradient ◽

Recording Instrument ◽

Short Intervals ◽

Fine Weather ◽

Yield Information ◽

Rapid Changes ◽

Continuous Record ◽

Lightning Discharges

This paper discusses the results of a series of observations of the potential gradient near the ground during thunderstorms. The recording instrument is intermediate in speed between the ordinary methods used for recording the potential gradient in fine weather and the high-speed oscillographs employed for detailed study of the variation of the field during short intervals of time. It yields a continuous record of the potential gradient and will also follow fairly rapid changes, the limit being set by the time of response of the electrometer which is less than 0.05 sec. The records thus yield information which would be missed by slower or by very rapid recording instruments. The observations extended over the years 1926—36 and were mostly made during the summer months.

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Comparative Analysis of Ionic Strength Tolerance between Freshwater and MarineCaulobacteralesAdhesins

Journal of Bacteriology ◽

10.1128/jb.00061-19 ◽

2019 ◽

Vol 201 (18) ◽

Cited By ~ 2

Author(s):

Nelson K. Chepkwony ◽

Cécile Berne ◽

Yves V. Brun

Keyword(s):

Ionic Strength ◽

Physicochemical Properties ◽

Bacterial Adhesion ◽

Marine Bacterium ◽

Caulobacter Crescentus ◽

High Ionic Strength ◽

Chemical Compositions ◽

Shear Forces ◽

Surface Attachment ◽

Content Type

ABSTRACTBacterial adhesion is affected by environmental factors, such as ionic strength, pH, temperature, and shear forces. Therefore, marine bacteria must have developed adhesins with different compositions and structures than those of their freshwater counterparts to adapt to their natural environment. The dimorphic alphaproteobacteriumHirschia balticais a marine budding bacterium in the cladeCaulobacterales.H. balticauses a polar adhesin, the holdfast, located at the cell pole opposite the reproductive stalk, for surface attachment and cell-cell adhesion. The holdfast adhesin has been best characterized inCaulobacter crescentus, a freshwater member of theCaulobacterales, and little is known about holdfast compositions and properties in marineCaulobacterales. Here, we useH. balticaas a model to characterize holdfast properties in marineCaulobacterales. We show that freshwater and marineCaulobacteralesuse similar genes in holdfast biogenesis and that these genes are highly conserved among the species in the two genera. We determine thatH. balticaproduces a larger holdfast thanC. crescentusand that the holdfasts have different chemical compositions, as they containN-acetylglucosamine and galactose monosaccharide residues and proteins but lack DNA. Finally, we show thatH. balticaholdfasts tolerate higher ionic strength than those ofC. crescentus. We conclude that marineCaulobacteralesholdfasts have physicochemical properties that maximize binding in high-ionic-strength environments.IMPORTANCEMost bacteria spend a large part of their life spans attached to surfaces, forming complex multicellular communities called biofilms. Bacteria can colonize virtually any surface, and therefore, they have adapted to bind efficiently in very different environments. In this study, we compare the adhesive holdfasts produced by the freshwater bacteriumC. crescentusand a relative, the marine bacteriumH. baltica. We show thatH. balticaholdfasts have a different morphology and chemical composition and tolerate high ionic strength. Our results show that theH. balticaholdfast is an excellent model to study the effect of ionic strength on adhesion and provides insights into the physicochemical properties required for adhesion in the marine environment.

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