An unknown microbial specimen measures 18 millimetres under a total magnification of 400 x , when examined under the microscope. What is the actual size of the unknown specimen? \( \begin{array}{ll}\text { (A) } 45 \text { micrometres. Total magnification }=400 x \\ \text { (B) } 4.5 \text { micrometres. } \quad \frac{18}{400 x}=0.045 \mathrm{~mm} \\ \text { (C) } 0.45 \text { micrometres. } \\ \text { (D) } 0.045 \text { micrometres. } & \text { micrometers }=0.045 \times 1000=45 \text { micrometers }\end{array} \)

(A) (i) Describe TWO disadvantages of using Replicate Organism Detection And Counting (RODAC) plate during a surface swab. (ii) Explain TWO purposes of conducting a hand swab test. 12 m

Glycerol a) Name the: (i) Process \( X \) (ii) Enzyme \( Y \) (iii) Molecule Z

(A) State ONE example of selective media that can be used to isolate [3 marks] EACH of the following microorganisms. (i) Gram positive bacteria. (ii) Staphylococci spp. (iii) Gram negative bacteria.

Calculate the cfu/cm \( \mathrm{cm}^{2} \) for a tested surface of 4 cm in length and 3 cm in width if the number of colonies on the agar plate is 96 cfu. (A) \( 8 \mathrm{cfu} / \mathrm{cm}^{2} \) (B) \( 12 \mathrm{cmu} / \mathrm{cm}^{2} \). (C) \( 72 \mathrm{cmu} / \mathrm{cm}^{2} \) (D) \( 128 \mathrm{cmu} / \mathrm{cm}^{2} \)

34 (A) (i) Explain ONE purpose of air monitoring. (ii) Describe TWO factors that will affect air quality.