Present-day high-yield penicillin production relies on improved strains of which species (historically including mutants such as Q-176 and Q-179)?

Introduction / Context:
After the initial discovery of penicillin, industrial production shifted to Penicillium chrysogenum due to its superior yields. Through classical strain improvement (mutation/selection), specific mutants such as Q-176 and Q-179 became benchmarks for increased penicillin production, paving the way for today’s even more productive lines.

Given Data / Assumptions:

• Industrial penicillin producers are P. chrysogenum strains.
• Q-176 and Q-179 are historically significant high-yield mutants.
• “Present-day high yielding” refers to the lineage derived from these mutants.

Concept / Approach:
While the foundational wild-type strain NRRL 1951 was crucial, subsequent mutants like Q-176 delivered substantial yield improvements and became standard industrial workhorses for many years. Modern strains often descend from or build on these improvements. Among the options, Q-176 is emblematic of high-yield production lines historically recognized in industry.

Step-by-Step Solution:
Identify the producing species: Penicillium chrysogenum.Distinguish between wild-type (NRRL 1951) and improved mutants (Q-176, Q-179).Select a representative high-yield mutant used widely: Q-176.Acknowledge that modern strains may surpass these but trace lineage back to them.

Verification / Alternative check:
Industrial histories and strain lineages cite Q-176/Q-179 as classic high-yield mutants, often preceding proprietary super-producing strains.

Why Other Options Are Wrong:
NRRL 1951: important progenitor but not the archetypal high-yield strain.Q-179: also high-yield, but the question requires a single choice; Q-176 is at least as emblematic and widely cited.None of the above: contradicts well-documented industrial practice.

Common Pitfalls:
Assuming the original wild-type remained the industrial standard; ignoring the extensive mutation/selection programs that transformed yields.

Final Answer:
Penicillium chrysogenum (Q-176)