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Related Concept Videos

Virtual Work01:20

Virtual Work

1.4K
The principle of virtual work states that if a body is in static and dynamic equilibrium, then the sum of all the virtual work done by all external forces and couple moments for any given virtual displacement must be zero.
In static equilibrium, a body can experience an imaginary or virtual movement, such as displacement or rotation. The virtual work done by a force is equal to the dot product of force and virtual displacement in the direction of the force. When it comes to virtually rotating a...
1.4K
Bacterial Transformation01:33

Bacterial Transformation

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In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
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Bacterial Cell Wall01:22

Bacterial Cell Wall

4.1K
The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and protecting against osmotic stress. This rigid yet flexible structure primarily comprises peptidoglycan, a polymer that forms a mesh-like matrix conferring mechanical strength and flexibility.Peptidoglycan Composition and StructurePeptidoglycan, the core of the bacterial cell wall, comprises alternating units of N-acetylglucosamine (NAG) and...
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Principle of Virtual Work: Problem Solving01:13

Principle of Virtual Work: Problem Solving

1.7K
The principle of virtual work is an essential concept in the field of mechanics and engineering. This is used to solve problems related to the equilibrium of a structure or system. It is based on the assumption that if a system is in equilibrium, the work done by all the forces during a virtual displacement is zero. This principle is applied by considering virtual displacements of the system and the corresponding work done by internal and external forces.
To apply the principle of virtual work,...
1.7K
Bacterial Signaling01:30

Bacterial Signaling

41.3K
Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell...
41.3K
Virtual Work for a System of Connected Rigid Bodies01:06

Virtual Work for a System of Connected Rigid Bodies

770
Virtual work is a powerful method used to solve problems involving several connected rigid bodies. When the system is in equilibrium, virtual work is zero. This allows the calculation of the resulting forces when a system undergoes a virtual displacement. When attempting to analyze such a system, first, use a free-body diagram, where an independent coordinate represents the configuration of the links, and mark its deflected position resulting from the positive virtual displacement.
Next,...
770

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Related Experiment Video

Updated: Feb 13, 2026

ScanLag: High-throughput Quantification of Colony Growth and Lag Time
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High-Throughput Quantification of Bacterial-Cell Interactions Using Virtual Colony Counts.

Stefanie Hoffmann1, Steffi Walter1, Anne-Kathrin Blume2

  • 1Project Group 5, Robert Koch Institute, Wernigerode, Germany.

Frontiers in Cellular and Infection Microbiology
|March 3, 2018
PubMed
Summary

The virtual colony count (VCC) method offers a high-throughput alternative to traditional colony forming unit (CFU) counting for quantifying bacteria in cell culture infection models. This label-free technique accurately measures bacterial growth kinetics, correlating it with initial bacterial numbers for robust host-pathogen interaction studies.

Keywords:
Salmonellaadhesionbacterial quantificationcell culture infection modelgentamicin protection assayintracellular replicationinvasionvirtual colony count

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Area of Science:

  • Microbiology
  • Infectious Diseases
  • Biotechnology

Background:

  • Accurate bacterial quantification is crucial for understanding host-pathogen interactions and pathogenicity.
  • Traditional colony forming unit (CFU) counting is labor-intensive and not high-throughput compatible.
  • The virtual colony count (VCC) method offers a potential automation-compatible alternative.

Purpose of the Study:

  • To adapt and validate the virtual colony count (VCC) method for quantifying *Salmonella enterica* sv. Typhimurium (*S*. Typhimurium) in cell culture infection models.
  • To compare VCC with traditional CFU counting.
  • To assess VCC's ability to identify bacterial phenotypes and test anti-invasion strategies.

Main Methods:

  • Adaptation of the VCC method using quantitative growth kinetics and calibration curves.
  • Application of VCC in HeLa, MDCK, and RAW macrophage infection models with *S*. Typhimurium.
  • Side-by-side comparison of VCC with CFU counting.
  • Evaluation of VCC for assessing bacterial mutant phenotypes and probiotic inhibition of invasion.

Main Results:

  • VCC showed good correlation with CFU counts in HeLa cell infections.
  • VCC successfully reproduced expected phenotypes of *S*. Typhimurium mutants in MDCK cells and RAW macrophages.
  • VCC demonstrated efficacy in evaluating the inhibitory effect of *E. coli* Nissle 1917 on *Salmonella* invasion.

Conclusions:

  • The adapted VCC method provides a flexible, label-free, and automation-compatible approach for quantifying bacteria in *in vitro* infection assays.
  • VCC is a reliable alternative to CFU counting, suitable for high-throughput screening and characterization of host-pathogen dynamics.
  • This methodology facilitates the study of bacterial pathogenicity and the evaluation of potential therapeutic interventions.