Which of the following statement is true about bacteriophage –
Correct Answer: It imparts toxigenicity to bacteria
Description: When a bacteria becomes lysogenized, occasionally, extra genes carried by the phage gets expressed in the
bacteria. This gene can change the properties of the bacteria. This process is known as lysogenic
conversion or phage conversion.
Example: Lysogenic conversion in corynebacterium diphtheria converts it into pathogenic bacteria. After
lysogenic conversion, C. diphtheria acquires the ability to produce toxin.
Bacteriophage
• Bacteriophages are viruses that infect bacteria.
• Bacteriophages resemble most viruses in having a protein coat called a capsid that surrounds a
molecule of DNA or RNA.
• Typical phages have hollow heads (where DA or RNA is stored) and tunnel tails.
The tail possesses many fibres. The fibres ha%re the ability to bind to specific molecules on the bacterial
cell surface.
• When a phage binds to bacterial cell surface it is called adsorption. The phage then undergoes
penetration, in which the viral DNA is injected through the tail into the host.
Types of phages: Lytic or virulent phages and Temperate or prophages
1. Lytic or virulent phages:
Lytic phages multiply inside the cell and release a burst of phages through the membrane, lysing the cell.
2. Prophages or temperate phages:
Prophages or temperate phages, on the other hand, do not immediately lyse the bacteria they infect. Instead,
they integrate their DNA into host DNA creating a phage.
The phage DNA in this repressed state is called a prophage (because it is not a phage but it has the potential
to produce phage)
The integrated state of phage DNA is termed prophage, whereas, the process is known as lysogeny and the
bacteria harbouring the prophage are called lysogenic bacteria.
Since the prophage contains genes, it can. confer new properties to the bacteria.
When a bacteria becomes lysogenized, occasionally, extra genes carried by the phage gets expressed in the bacteria. This gene can change the properties of the bacteria. This process
is known as lysogenic conversion or phage conversion.
Lysogenic conversion in Corynebacterium Diphtheria converts it into pathogenic bacteria. After lysogenic conversion, C. diphtheria acquires the ability' to produce toxin.
Lysogenic conversion is also seen in Salmonella typhi and Clostridium botulinum.
Transduction
Transduction occurs when bacteriophage carries a piece of bacterial DNA from one bacterium to another.
• Transduction is not only confined to transfer of chromosomal DNA, episomes and plasmid may also be transduced.
• The plasmid is a DNA molecule that is separate from and can replicate independently of chromosomal.
• Types of transduction.
• Lytic phages cause generalized transduction.
• Temperate phages cause specialized transduction
Category:
Microbiology
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