Final answer:
The log phase of bacterial growth is when metabolic activity reaches its peak due to rapid and exponential cell division, making it a critical point for both industrial applications and the effectiveness of antibiotics like penicillin.
Step-by-step explanation:
Metabolic activity is at maximum level in the log phase of growth. During the log phase, also known as the exponential growth phase, cells rapidly divide and increase in number in an exponential manner. The bacteria are very active metabolically during this phase, which makes them particularly susceptible to antibiotics that target vital processes such as protein, DNA, and cell-wall synthesis. Penicillin, for instance, is most effective during the log phase because it inhibits cell-wall synthesis, impacting the rapidly dividing cells.
In industrial applications and research, cells in the log phase are preferred due to their constant growth rate and uniform metabolic activity. Not only does this phase allow for the accumulation of a large microbial mass needed for various products, but it is also the point at which cells are most vulnerable to interventions.