A growing bacterial culture doubles in 1 hr; the increase in cell mass in 30 minutes will be:
A. Zero,
B. 50%,
C. Less than 50%,
D. More than 50%,

How Does Bacterial Growth Work?

Bacterial growth follows an exponential pattern, meaning that the population size and cell mass increase in a predictable manner. The key factor determining growth rate is the doubling time, which is the time required for a bacterial population to double in number.

Understanding the Growth Rate

In this scenario, the bacterial culture doubles every 1 hour (60 minutes). This means that if you start with X amount of bacterial cells at time 0, after 60 minutes, it will become 2X. Now, the question is: How much does the cell mass increase in just 30 minutes?

Calculation of Cell Mass Increase in 30 Minutes

Since bacterial growth follows an exponential equation:

Nt = N0 × 2^(t/T)

Where:

• Nt = Final population size at time t
• N0 = Initial population size
• T = Doubling time (60 minutes in this case)
• t = Time elapsed (30 minutes)

Substituting values:

N30 = N0 * 2^(30/60)

N30 = N0 * 2^(1/2)

Since 2^0.5 ≈ 1.414, the cell mass increases by 41.4% in 30 minutes.

Answer to the Question:

• A. Zero – Incorrect, because bacterial cells are continuously dividing.
• B. 50% – Incorrect, because growth is exponential, not linear.
• C. Less than 50% – Correct! The increase in cell mass is around 41.4%, which is less than 50%.
• D. More than 50% – Incorrect, since 41.4% is below 50%.

Key Takeaways

• Bacterial growth follows exponential growth, not linear.
• In 30 minutes, the cell mass increases by 41.4%, not 50%.
• The correct answer is C: Less than 50%.

By understanding these fundamental growth patterns, researchers and microbiologists can better predict bacterial behavior in laboratory and real-world settings.