Which of the following is a common indicator that a pathogenicity island is present in the genome of a bacterium?

• A. The region contains only housekeeping genes.
• B. The region lacks any mobile genetic elements.
• C. The region has a significantly different GC content compared to the rest of the genome.
• D. The region is always located at the origin of replication.

Answer: (C)

Verified step by step guidance

1. Understand what a pathogenicity island (PAI) is: a distinct genetic element in the genome of pathogenic bacteria that contains genes contributing to virulence.
2. Recall that PAIs often have different characteristics compared to the rest of the bacterial genome because they are acquired through horizontal gene transfer.
3. Identify common indicators of PAIs, such as the presence of virulence genes, association with mobile genetic elements (like transposons or phages), and differences in nucleotide composition.
4. Focus on the GC content: PAIs typically have a significantly different GC content compared to the host genome because they originate from different species with distinct genomic signatures.
5. Conclude that among the options, the presence of a region with a significantly different GC content is a strong indicator of a pathogenicity island.