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Figure 1. shows the fraction of strains with particular phelnotypes during seria

ID: 178562 • Letter: F

Question

Figure 1. shows the fraction of strains with particular phelnotypes during serial passage into new media. ?Rate the virulence factor type 1 fimbriae, and aerobactin as constitutive or inducible, and explain your interpretation?

100 80 80 40 20 7 14 21 Days of Serial Passage (Agar and Broth FIG. 1. Percentage of strains expressing virulence factors when tested repeatedly during serial passage. The results shown are from passage on 5% sheep blood agar (Pfimbriae [B] and hemolysin (OD, on supplemented M9 agar plus 2,2'-dipyridyl (aerobactin production (O), in Luria broth (aerobactin utilization (AD, or in brain heart infusion broth (type 1 fimbriae lol). The symbols indicate the day(s) on which virulence factor tests were performed.

Explanation / Answer

The virulence factor aerobactin is constitutive. This is because, the % of expression of virulence factor was constant in luria broth and was about 60% and above from 0 to 14 hours of incubation. The virulence factor type 1 fimbriae is inducible because the initial expression of virulence factor was at above 20% initially at 0 hours and gradually increased upto above 80% at 21 hours. The type 1 fimbriae are observed on brain heart infusion broth which induces the expression of type 1 fimbriae.

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