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Related Concept Videos

Ionic Strength: Overview01:12

Ionic Strength: Overview

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The ionic strength of a solution is a quantitative way of expressing the total electrolyte concentration of a solution. This concept was first introduced in 1921 by two American physical chemists, Gilbert N. Lewis and Merle Randall, while describing the activity coefficient of strong electrolytes. During the calculation of ionic strength (I or μ), all the cations and anions are considered. However, the concentration (c) of an ion with a greater charge number (z) has a greater contribution...
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Ionic Strength: Effects on Chemical Equilibria01:19

Ionic Strength: Effects on Chemical Equilibria

3.0K
The addition of an inert ionic compound increases the solubility of a sparingly soluble salt. For example, adding potassium nitrate to a saturated solution of calcium sulfate significantly enhances the solubility of calcium sulfate. Le Châtelier's principle cannot predict this shift in the equilibrium. Instead, this could be explained in terms of changes in the effective concentration of the ions in solution in the presence of added inert salt.
In this solution, the primary...
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Factors Affecting Activity Coefficient01:17

Factors Affecting Activity Coefficient

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The extended Debye-Hückel equation indicates that the activity coefficient of an ion in an aqueous solution at 25°C depends on three partially interdependent properties: the ionic strength of the solution, the charge of the ion, and the ion size. 
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a...
1.8K
Ionic Association01:28

Ionic Association

164
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
164
Electrolytes: van't Hoff Factor03:08

Electrolytes: van't Hoff Factor

37.5K
Colligative Properties of Electrolytes
The colligative properties of a solution depend only on the number, not on the identity, of solute species dissolved. The concentration terms in the equations for various colligative properties (freezing point depression, boiling point elevation, osmotic pressure) pertain to all solute species present in the solution. Nonelectrolytes dissolve physically without dissociation or any other accompanying process. Each molecule that dissolves yields one...
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Colloidal precipitates01:09

Colloidal precipitates

6.8K
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
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Measuring Transcellular Interactions through Protein Aggregation in a Heterologous Cell System
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Role of Ionic Strength in Staphylococcal Cell Aggregation.

Thomas Vanzieleghem1, Numa Couniot1, Philippe Herman-Bausier1

  • 1Laboratory of Food and Environmental Microbiology, Applied Microbiology, Earth and Life Institute, ‡Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), and §Institute of Life Sciences, Université catholique de Louvain , Croix du Sud 2, L7.05.12, B-1348 Louvain-la-Neuve, Belgium.

Langmuir : the ACS Journal of Surfaces and Colloids
|July 2, 2016
PubMed
Summary

Staphylococcus bacteria can rapidly form cell aggregates solely based on ionic strength. This environmentally triggered aggregation is reversible and offers new insights into bacterial behavior and control.

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Area of Science:

  • Microbiology
  • Biophysics
  • Cellular Biology

Background:

  • Cell aggregation is crucial for Staphylococcus pathogenesis and biofilm formation.
  • Environmental influences on staphylococcal aggregation, particularly ionic strength, are not well understood.
  • Previous research focused on molecular mechanisms, overlooking environmental factors.

Purpose of the Study:

  • To investigate the novel phenomenon of staphylococcal cell aggregation induced solely by ionic strength.
  • To elucidate the role of environmental factors in Staphylococcus aggregation.
  • To understand the reversibility and strain-dependency of this aggregation.

Main Methods:

  • Tested 14 Staphylococcus strains and other Gram-positive species for aggregation in varying ionic strength buffers.
  • Utilized Atomic Force Microscopy (AFM) with functionalized tips to analyze cell surface properties.
  • Investigated the effect of different ionic strengths on cell surface charge and adhesion.

Main Results:

  • Seven Staphylococcus strains exhibited rapid, large cell cluster formation within minutes at 1.5-50 mM ionic strength.
  • Other Gram-positive species did not show this aggregation phenotype.
  • AFM confirmed that ionic strength modulates cell surface charge, influencing adhesion.
  • Aggregation was reversible, with aggregates dispersing in higher ionic strength solutions.
  • Optimal ionic strength for aggregation varied by strain.

Conclusions:

  • Staphylococcal isolates possess a unique aggregation mechanism responsive to ionic strength.
  • Ionic strength acts as an external stimulus, rapidly triggering reversible cell aggregation.
  • This ionic strength-dependent aggregation is a previously unreported phenomenon in staphylococci.
  • Findings suggest new avenues for controlling staphylococcal growth and biofilm formation.