What will happen if a bacteria acquires genes coding for restriction endonuclease aEUR’
Correct Answer: Bacteria will die as lacks methylase
Description: Bacteria will die as it lacks methylase Bacterias are susceptible to attack by viruses known as bacte- riophages. Bacterias have developed their defense mechanism to protect themselves .from the bacteriophages. The system that bacterias possese against the phage viruses is the restriction modification system? This system consists of restriction endonuclease enzyme and a methylase enzyme. Each bacterial species and strains have their own combination of restriction and methylating enzymes i.e., restriction modification system is species specific Restriction enzyme These are enzymes present in baeteria that recognize specific base sequences in the D.N.A. and, cut the DNA at that site (restriction site). - A restriction enzyme acts as biochemical scissors and are therefore called restriction endonuclease. Bacterias use this enzyme in defense against phage viruses (bacteriophages) When a phage virus infects bacteria it inses its DNA into bacteria so that it gets replicated The restriction enzyme prevents this replication by cutting the D.N.A of the phage virus into many pieces. - When a strain of bacterias lacking restriction enzyme is infected with phage virus most viruses can initiate a successful infection - When the same strain contains a restriction enzyme, however, the probability of successful infection decreases The presence of additional restrictive enzymes has multiplicative effect. A bacteria with four to .five restriction enzyme would be viually impregnable. The bacterial cell uses the restriction enzyme to cut the invading DNA of the virus at a specific site. This prevents the virus replication. But bacterial DNA will also contain sites that could be cleaved by the restriction enzyme. How is the bacterial cell protected. from auto destruction by restriction endonuclease???. Restriction enzyme usually occur in combination with one or two modification enzymes (DNN- methylasetransferase) that protects the cells own DNA from cleavage by the restriction enzytne Modification enzymes recognize the same DNA sequences as the restriction enzymes that they accompany, but, instead of cleaving the sequence they methylate one of the bases in each of the DNA strands. The methyl groups protrude in to the major groove of DNA at the binding site and prevents the restriction enzyme from acting upon it. "So the viral DNA is restricted in the bacterial cell by restriction enzymes and the bacterial DNA is modified by the methylase and is provided protection from its own restriction enzyme" -It is impoant to note that the restriction modification system is species specific i.e., each bacterial species has its own restriction modification enzyme. It is significant because the restriction enzyme may kill any virus that invade the bacteria but the methylase enzyme can only protect that paicular bacteria from lysis because it will recognize those bacterial DNA as host and protect it against restriction endonuclease. If a bacteria acquires new restriction endonuclease it would also lyse bacterial DNA because the bacteria does not have the species specific methylase enzyme to protect its DNA from the newly acquired restriction endonuclease.
Category:
Microbiology
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