25 Bacteriophage Titer Flashcards
How to viruses reproduce?
- the hijacking of a cells protein synthesis machinery
What is the smallest unit of a virus? Characteristics?
- virion/virus particle
- lack cell structure and independent metabolism
What are viruses that infect bacteria called?
-bacteriophages/phages
What are the hallmarks of life that viruses show?
- they reproduce
- have an ordered structure consisting of proteins, nucleic acids, and other biological molecules
- express genetics info found in nucleic acids in order to build proteins
- they evolve
Structure of a T4 phage virion
- consists of proteins and DNA
- proteins form the outer structure known as a capsid
- protein capsid includes a head, tail sheath, base plate, and tail fibers
- the DNA inside the head contains the genetic info that the phage use to reprogram a host cell into making more phage
Visual representation of a T4 phage lytic cycle
What is phage therapy?
-treating human infections with phages
What are the advantages of phage therapy compared to antibiotic medications
1) if the bacteria infecting a person are exposed to a small number of compatible phage virions, the phage will kill the bacteria and reproduce at the same time.
- self sustaining
- only 1 dose of phage needs to be delivered to the infecting bacteria
- once the infecting bacteria are destroyed , the page stops reproducing and is eventually degraded by the normal enzymes found in human tissues
2)ability of a phage to co-evolve with their host bacteria
What are the disadvantages of phage therapy?
1) the need to precisely match the infecting bacteria with a phage that can destroy it
- phages are very selective about which host cells they can bind to and destroy
2) phages have an outer protein coat
- this coat is not acid and enzyme resistant, which means that orally administered phage virions are often destroyed by stomach acids and digestive enzymes
3) the capsids of phage virions are recognized and targeted by the immune system due to i being complicated
What is a phage titer?
-the count of phage virions in a sample
- a concentration, the number of virions per unit of volume.
- usually report phage counts as plaque forming units per milliliter (PFU/ml)
What is the equation to calculate phage titer?
What is the purpose of serial dilution?
- producing a concentration which will give an easily counted number of plaques
- this allows the creating of countable plates from samples with widely varying timers
What are the dilution factors we used in lab?
T4 phage can infect some strains of E.COli and Shiella. What does this suggest about the degree of genetic similarity between E.coli and shigella?
-both are from the same species
What is a lawn?
What is a plaque?
A lawn is the confluence later of bacteria on a culture plate.
A plaque are the clearings within the lawn of a culture plate
