Final answer:
Bacterial DNA is protected from restriction endonucleases through methylation, which adds methyl groups to specific cytosine nucleotides, preventing these enzymes from cleaving the bacterium's own DNA.
Step-by-step explanation:
Bacterial DNA is protected from the action of restriction endonucleases by methylation. This process involves the addition of methyl groups to certain cytosine nucleotides in DNA, which prevents the restriction endonucleases from recognizing and cleaving the bacterium's own DNA. These enzymes typically cut DNA at specific sequences unless those sequences are methylated. Thus, methylation is the mechanism by which bacterial cells distinguish their own DNA from foreign DNA (such as that from invading viruses), and it protects their genetic material from being degraded by restriction enzymes. This protection is a crucial component of bacterial defense mechanisms and is a unique aspect of epigenetic regulation in prokaryotes.