A virologist has a cell-free extract of herpes simplex virus (HSV) that has a titer of 6 x 10^6 infectious virus particles/mL. This virus forms plaques on monolayers of the monkey kidney cell line, CV-1. Following completion of a 10-fold dilution series, the virologist plates 100uL of each sample in duplicate. Which of the following experimental results did he MOST LIKELY observe in the duplicate plates corresponding to his 1:10000 dilution? TMTC = Too Many to Count
(A) TMTC (Plate 1); TMTC (Plate 2)
(B) 61 (Plate 1); 59 (Plate 2)
(C) 96 (Plate 1); 97 (Plate 2)
(D) 8 (Plate 1); 10 (Plate 2)
(E) 26 (Plate 1); 24 (Plate 2)
Answer: (B) 61 (Plate 1); 59 (Plate 2)
The original stock has the concentration 6 × 10^6 infectious virus particles/ mL.
This was diluted by the factor 1:10000
This leaves:
(6,000,000) ÷ 10,000
= 600 inf virus particles/ mL
100 microL (0.1 mL) of this was plated.
Since 1 mL has a count of 600
0.1 mL has a count of 60.
Hence the answer is (B).
Alternatively, if 1 mL was plated,the answer would have been A: TMTC since a count of over 30 - 300 is the countable range.
A virologist has a cell-free extract of herpes simplex virus (HSV) that has a titer of...
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