Question

When bacteria are inoculated into a new sterile nutrient broth, their numbers don’t begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don’t bacterial numbers increase immediately?

A. The medium contains inhibitors that prohibit rapid growth of the bacteria, and these must be inactivated before bacterial numbers will increase.
B. The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes.
C. There are not enough nutrients for the bacteria to grow, and growth is delayed until there are some dead cells to cannibalize.
D. The bacteria have to establish a biofilm before their numbers can increase.

Answer 1

Answer: B. The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes.

Explanation: The lag phase is a time for adjustement to new environments, in this case new mediums. In that phase, bacteria sense the available nutrients to synthesize those required and grow as preparing for division, metabolizing to produce energy, making proteins, fatty acids, etc.

Answer 2

Answer: Option B is the correct answer.

Step-by-step explanation:

When bacteria is introduced into a medium it first has to adapt and secrete the necessary growth factors and enzymes that will aid in the digestion of nutrients found in this new medium. After lag phase follows exponential growth where bacteria grows at a rapid rate till it reaches a stationary phase due to nutrient depletion.