Growth and Control of Microorganisms - Environmental Microbiology - Environmental Science & Engineering Previous Year Questions

1

2024 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2024

With reference to disinfection, which of the following statement(s) is/are CORRECT?

A

Ethanol damages lipid structures in the bacterial cell membrane.

B

Mercuric chloride inactivates cellular enzymes containing sulfhydryl groups.

C

Glutaraldehyde inactivates protein.

D

Isopropyl alcohol cannot be used as a disinfectant.

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2

2025 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2025

If microbial growth occurs under substrate unlimited conditions, according to Monod’s kinetics, choose the correct option(s) from the following

A

Microbial growth follows zero order with respect to substrate concentration.

B

Microbial growth follows first order with respect to substrate concentration.

C

Specific growth rate is half of maximum specific growth rate.

D

Specific growth rate is almost equal to maximum specific growth rate.

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3

2021 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2021

In a sample, the growth of microbial cells started with an initial concentration of \(5\times10^4\) cells per millilitre (mL) of the sample. After a certain time period, the cell concentration was found to be \(1280\times10^4\) cells per mL of the sample. Assuming binary fission of cells and no cell death, the number of generations of cell growth occurred in this time period is __________ (answer in integer).

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4

2022 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2022

Ten litres of the sample was filtered through a membrane filter and the filter was transferred to solid agar media which supports growth of coliform organisms. After incubation at 37 °C for 48 hours, the agar plates showed an average of 64 colonies per plate. What was the average concentration of coliform organisms (in Colony Forming Units per unit volume) in the original water sample?

A

64 CFU/ml

B

640 CFU/ml

C

6.4 × 10³ CFU/ml

D

64 × 10³ CFU/ml

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5

2022 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2022

For an exponentially growing microbial culture, the specific growth rate (\(\mu\)) is related to its doubling time (\(t_d\)) by which one of the following relations?

A

\(t_d = \mu \)

B

\(t_d = \mu^2 \)

C

\(t_d = \frac{1}{\mu} \ln 2 \)

D

\(t_d = \frac{1}{2} \ln \mu \)

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6

2022 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2022

A microbial culture, with a specific growth rate of \(\mu_1\) (per hour), is being grown in a continuous reactor at steady state with hydraulic retention time (HRT) of 24 hours. This reactor is subjected to a perturbation by reducing the HRT to 12 hours. The reactor recovers from the perturbation and comes to a new steady state with a new specific growth rate of \(\mu_2\) (per hour). Which one of the following statements is correct?

A

\(\mu_1 = \mu_2 \)

B

\(\mu_1 = 0.5 \mu_2 \)

C

\(\mu_2 = 0.5 \mu_1 \)

D

\(\mu_2 = e^{0.5} \mu_1 \)

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7

2026 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2026

Which ONE of the following options CORRECTLY matches the processes associated with the growth condition given in the table?

A

(P) - (ii); (Q) - (iii); (R) - (iv); (S) - (i)

B

(P) - (iii); (Q) - (ii); (R) - (iv); (S) - (i)

C

(P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)

D

(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

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8

2026 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2026

In a batch culture experiment, 2 cells of a microorganism were added to a growth medium. During the experiment, a lag phase of 1 hour was first experienced by the added cells, in which no cell multiplication occurred. Afterwards, cells started multiplying exponentially with a doubling time of 1 hour.
After total 8 hours of experiment, the number of cells present in the growth medium was _____ (answer in integer).

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9

2026 · Environmental Science & Engineering · Environmental Microbiology · Growth and Control of Microorganisms

Environmental Science & Engineering (ES) 2026

A thermal process, at a specific temperature, results in 2-log₁₀ removal of non-thermotolerant pathogenic microorganisms from a water sample in 20 min.
The time needed to achieve 99.999% removal of these microorganisms under similar condition is _____ min (answer in integer).

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