Bacteriophage basics Flashcards
How many genes are in the typical phages (dsDNA tailed)
50-250 genes
What must be required for a successful plaque assay?
Multiple rounds of phage infection and growth
Why do lytic phages generally form clear plaques?
They kill the bacteria
What does a phage have to be able to interact with in a host bacteria?
The host cellular machinery including the host transcription and translation systems
What happens to the phage genome in the lysogenic cycle?
It becomes stably maintained within the cell, even through many subsequent generations of cell division
How do bacteriophages replicate?
They require a bacterial host and take advantage of the host’s cellular machinery and redirecting it toward viral reproduction
What are some other less known structures of phages?
Single stranded DNA or RNA can can be enveloped with a lipid membrane, have one or than one chromosome, or have a variety of other configurations
Are bacteriophage particular to hosts? If so, how?
Yes, the host range can be a single bacteria strain or it can span multiple bacterial species or genera. However, there are few if any phages with a host range that spans different bacterial orders and the possibility of spanning different phyla is even less likely
When the bacterial host cell is lysed and the new virions are released. Part of the lytic cycle
Phase 6 - Cell lysis and phage release
How simple can it be for phages to alter their host ranges?
Sometimes a single base mutation in their genome is enough to alter their host range
How long does it take G. terrae to form a lawn in lab?
2-3 days
When prophage-encoded and expressed proteins alter the host cell surface in such a way that other phages are excluded from adsorption and DNA injection
Exclusion
When the phage chromosome circularizes inside the host cell. Part of the lytic cycle
Phase 2 - Phage DNA circularization
What is morphology?
The color, size, and shape. The characteristics that vary between species
What are virions?
Late-gene products that are the structural proteins that comprise the new phage particle. The new phages
What is a common mechanism used by prophages to ensure its stability?
Integrating into the host chromosome through a process known as homologous recombination
What is the estimated number of phage population?
10^31 particles
What are the main parts of a bacteria?
A flagellum, cell wall, cytoplasmic membrane, cytoplasm, capsule, pili, ribosomes, and bacterial DNA
What happens when a prophage is integrated in a lysogen (host cell)?
The prophage is replicated by the host DNA polymerases and passed to both daughter cells during normal cell division
What is it called when we provide bacteria a media to grow in without other bacteria?
culturing bacteria
What happens to the genes required for the lytic cycle in the lysogenic cycle?
They are repressed, rather than expressed
How many bacteria are generally in a colony?
generally 10^7-10^8 cells
What are the percentages of a phage entering the lytic and lysogenic cycles?
80-90 go to lytic and 10-20 go to lysogenic
What do G. terrae colonies look like?
orange, round, rough, and dry in texture
