Lecture 8 Microbes 4 Flashcards
Endosymbiosis is
a special case of horizontal gene transfer involving an entire genome.
Some genes transferred into host genome as well
Endosymbiotic theory evidence (2) between archaea and bacteria
Morphological similarity
DNA similarity (molecular phylogenetics)
Virus generally is (5)
Protein package containing DNA or RNA.
Not considered a cell, incapable of replication without a host
Use host resources (nucleotides, amino acids) to replicate.
Some are more virulent (killing) than others.
LUCA probably had viruses.
Composition of Corona virus (6)
RNA, protein coat (capsid), lipid bilayer, membrane proteins (spike, membrane, envelope)
Process of Corona virus infection
It can infect other animals other than humans.
Its adaption in other species could lower its ability to infect human
What is phage and its characteristics (1+2)?
A phage is a virus that infects bacteria or archaea.
They are highly diverse in size, shape and gene.
They have linear DNA, 3000 to 500k base pairs
Process of phages as vectors of HGT
(2 cycles)
Lytic cycle: normal infection, phage applies selective pressure on vibrio cholerae
OR
Lysogenic cycle: HGT happens, cholera toxin is a phage integrated into bacteria
The importance of phage (2)
They are vectors of HGT.
They target the most abundant bacteria (phage therapy)
Coevolution is
mutually imposed selective pressures. There are adaptation or counter-adaptation.
Most V. cholerae isolates from a patient’s stool sample are resistant to phages. Why?
Resistant mutants infect host less effectively.
Stages of coevolution (3) between phage and bacteria
Infection: a phage must attach to receptor protein on bacteria
Mutations in receptor gene can resist phage
Phage are then under selection to bind to mutated receptor.
