CELS 191 Lecture 33 Flashcards
(21 cards)
what is horizontal gene transfer
transfer of plasmids from one bacteria to another
what is vertical gene transfer
from parent to offspring
what are two important attributes transferred horizontally by bacteria
virulence factors and antibiotic resistance
what are virulence factors
attributes that help bacteria survive in the host, sometimes at a cost to the host
what is antibiotic resistance in bacteria
attributes that reduce the effectiveness of antibiotics against the targeted bacteria
what are the three methods of horizontal gene transfer
transformation
transduction
conjugation
what is transformation in terms of horizontal gene transfer
transformation involves the uptake of short fragments f naked DNA by naturally transformable bacteria
what is transduction in terms of horizontal gene transfer
transduction involves the transfer of DNA from one bacterium into another via bacteriophages
what is conjugation in terms of horizontal gene transfer
conjugation involves transfer of DNA material via sexual pilus and requires cell-cell contact
how does conjugation occur
when two bacteria meet and one has a sexual pilus they can join and pas DNA. plasmids unwind and get passed through from one bacteria to another
what are the requirements for conjugation
the bacteria have to be Alvie and they generally also have to be the same species of bacteria
during transduction how does the bacteriophage attach itself
the tips of the tail fibres of bacteriophages have highly specific sets of ligands which attach to bacterial receptors
during transaction what occurs after the bacteriophage has attached
it squats down and inserts the DNA from the head into the bacteria
does just one bacteriophage hit the bacteria at once
no - multiple bacteriophages hit the same bacteria at the same time
during transduction what occurs after the bacteriophage has inserted its DNA
the DNA is essentially manufacturing instructions which cause the bacteria to produce lots of different parts needed to produce more bacteriophages
during transduction after the bacteria has produced the components of the bacteriophage what happens
these parts are assembled, however, during the assembly mistakes are made and sometimes instead of putting the bacteriophage DNA into the capsid it puts a plasmid in there
is it common for bacteriophages to accidentally put plasmids into the capsids during assembly
yes, this mistake is so common that labs use it as a technique to transfer DNA
during transduction does the bacteriophage still function properly if a plasmid is put into the capsid
yes - the phage still works just as efficiently and when the phages are released they go on to inject that plasmid into another bacteria
what is phage therapy
the therapeutic use of bacteriophages to treat pathogenic bacterial infections
what are the advantages of phage therapy
it is very specific and affects only the targeted bacterial species
they replicate as the site of infection
they occur naturally (easy to locate)
safe (no reports of serious adverse effects)
active against antibiotic resistant bacteria
what are the disadvantages of phage therapy
additional research required
development of phage resistant and phage neutralising antibodies
not accessible to intercellular pathogens
difficult to administer
can transfer toxin gene between bacteria
