Final answer:
The modified organism with a deleted suspected virulence gene will have a higher LD50 than the unmodified organism, indicating a reduction in virulence and hence decreased potency.
Step-by-step explanation:
If a suspected virulence gene is deleted from a pathogenic organism, and if the gene product did indeed decrease virulence, the modified organism will have a higher LD50 than the unmodified, gene-containing organism. This is because the LD50, or lethal dose required to kill 50% of the test population, is an indicator of the virulence of a pathogen. Inactivation of virulence genes results in a measurable loss of pathogenicity, meaning the organism is less potent and requires a higher dose to achieve the same lethal effect as before the gene was deleted.
In relation to the development of vaccines, methods such as excising or modifying virulence genes have been used to create recombinant organisms that can express surface antigens without causing disease. These organisms can prevent the adherence of naturally virulent bacteria by colonizing in the same environmental niche, such as the intestinal mucosa, and thus help in preventing the disease.