What is a bacteriophage plaque?
1 Introduction. A phage plaque is a clearing in a bacterial lawn. Plaques form via an outward diffusion of phage virions that is fed by bacterial infection. Anything that slows phage diffusion can impede plaque development and thereby plaque size.
What is a plaque assay?
The plaque assay can be used to purify a clonal population of virus or to determine viral titer as plaque-forming units per ml (pfu/ml) so that known amounts of virus can be used to infect cells during subsequent work. Each plaque represents a single virus. …
What causes the formation of plaques in a bacteriophage assay?
The basis of plaque assay is to measure the ability of a single infectious virus to form a “plaque” on a concurrent monolayer culture cells. A plaque is developed as a part of infection of one cell by a single virus particle that is followed by the replication of that virus, and finally, the death of the cell.
How is plaque assay calculated?
The titer of a virus stock can be calculated in plaque-forming units (PFU) per milliliter. To determine the virus titer, the plaques are counted. To minimize error, only plates containing between 10 and 100 plaques are counted, depending on the size of the cell culture plate that is used.
Are bacteriophages host specific?
Bacteriophages (“phages” for short) are viruses that infect bacteria. Phages are highly host-specific and will typically only infect and kill an individual species or even subspecies of bacteria.
What is a plaque in virology?
From Wikipedia, the free encyclopedia. A viral plaque is a visible structure formed after introducing a viral sample to a cell culture grown on some nutrient medium. The virus will replicate and spread, generating regions of cell destruction known as plaques.
How many viruses are needed to form a plaque?
One virus
How are plaques formed by bacteriophage?
Plaques are clear zones formed in a lawn of cells due to lysis by phage. The morphology of the plaque depends upon the phage, the host, and the growth conditions. Usually phage infection is studied in a layer of soft agar (or “top agar”) which allows the phage to diffuse rapidly.
What is a plaque purified virus?
Virus stocks prepared from a single plaque are called plaque purified virus stocks. To prepare such virus stocks, the tip of a small pipette is inserted into the agar overlay above the plaque. The viruses within the agar plug move into the buffer, which can then be used to infect cultured cells.
Is one plaque forming unit the same as one virus particle?
Theoretically, the plaque-forming unit includes only the infectious virus particles since a virus particle failing to infect a host cell will not be able to produce a plaque, hence, will not be counted. Thus, one PFU means one lytic event (or one infectious virus particle).
Why is agar needed in a plaque assay quizlet?
Virions. Active and infectious bacteriophage particles. It’s important to use hard agar with soft agar overlay because The hard agar underneath the soft agar overlay is where you make a lawn streak of your bacteria. Since phage can only grow in the presence of bacteria, this is the only way you can visualize plaques.
What is a plaque in microbiology?
Plaque, in microbiology, a clear area on an otherwise opaque field of bacteria that indicates the inhibition or dissolution of the bacterial cells by some agent, either a virus or an antibiotic. …
How do you describe plaque morphology?
Plaque morphologies can include bull’s eyes, clear plaques, sectored or star-shaped plaques, the plaques of T-even phage wild-type versus rapid lysis mutants (which are small with rougher borders versus larger with smoother borders), plaques containing central zones of turbidity as often associated with temperate …
Does a phage plaque grow to specific size?
Once the bacteria stop growing due to crowding and lack of nutrients, the phages can no longer successfully infect the bacteria and the plaque will not increase in size.
How do you isolate phages?
Phages are purified by removing, picking off, a well isolated plaque using either a Pasteur pipette or more crudely, but just as effectively, a wire loop. Using a sterile Pasteur pipette the area around the plaque is stabbed and pieces of soft area are ‘sucked’ into the pipette.
How do you isolate bacteriophage from soil?
With the enrichment method, all soil bacteria are removed from the soil extracted phage samples by filtration through a 0.22 µM filter. The sterile filtered lysate containing phage particles, but not soil bacteria, are diluted in 2x LB broth with the desired bacteria used as the phage propagation host.
How do you isolate bacteriophage from sewage?
Bacteriophage Isolation FROM SEWAGE
- Adsorption – A phage attaches to specific receptor sites on the surface of the host cell.
- Penetration – The phage tail fibers contract and the baseplate settles down on the cell surface.
- Biosynthesis – Once inside the cell, phage DNA redirects host cell metabolism.
What is phage buffer?
A plate lysate is simply a concentrated liquid sample of phage. It is obtained by infecting a plate of bacteria with the phage of interest, letting the phage lyse the cells, then adding buffer directly to the plate surface to collect the phages. Plate lysates are the standard for long‐term storage of a phage sample.
What is SM buffer?
Introduction: SM Buffer is a mixture of Sodium chloride, Magnesium sulphate and gelatin and is extensively used in molecular biology. This is used as a phage diluent and storage buffer as the gelatin stabilizes lambda phage. Application: SM Buffer is mainly used for routine manipulation of phage suspensions.
What titer is considered a high titer lysate?
Lysates with a final concentration greater than 109 PFU/ml are “High Titer” lysates. Current data suggest that the higher the titer, the more stable the lysate. Full plate titers have higher degree of accuracy.
How do you get a titer?
Counting and Calculating Titers To calculate the viral titer, Take your plates out of the incubator and examine them. You should see cloudy areas throughout the plate where bacteria have grown, except for small clear spots called plaques. These plaques are patches of dead bacteria, and each plaque represents one virus.
What is titer and how do we calculate it?
To calculate antibody titer, a blood serum sample containing antibody is diluted in serial ratios (1:2, 1:4, 1:8, 1:16…etc.). The assigned titer value is indicative of the last dilution in which the antibody was detected.
What is infectious titer?
Infectious titer: the concentration of viral particles that can transduce cells. Infectious titers are typically quantified by cell transduction assays. The specific infectivity of viral preparations is defined by the ratio of physical viral particles to infectious viral particles.
What is a TCID50 assay?
The TCID50 (Median Tissue Culture Infectious Dose) assay is one method used to verify the viral titer of a testing virus. Host tissue cells are cultured on a well plate titer, and then varying dilutions of the testing viral fluid are added to the wells.
What is VG titer?
Perhaps the most critical lot release assay for AAV vector preparations is the AAV vector genome (vg) titer assay, since genome copy numbers are universally used for dosing purposes in both preclinical and clinical studies. The most prevalent method for quantifying AAV vectors is currently quantitative PCR (qPCR).
What is IFU mL?
Functional titer, also known as infectious titer, is the measurement of how much virus actually infects a target cell. Functional titer may be expressed in the form of transduction units per mL (TU/mL), plaque-forming units per mL (pfu/mL), or infectious units per mL (ifu/mL), depending on the viral vector.