= Solution
Disrupting the dynamic <actin> network compromises processes required for sustained proliferation: <endocytosis>, directed delivery of <cell membrane> and cell-wall material, maintenance of <polarized cell growth> and successful <cytokinesis>. \b[Failure of these actin-dependent functions can cause growth arrest and, under sufficiently damaging conditions, loss of viability.] The altered sensitivity of <actin> mutants supports an actin-related mechanism, with their different assembly properties potentially changing the reserve of functional <cytoskeleton>.
A clear zone itself establishes failure to form a visible lawn, not necessarily death. <biological cells> might remain viable but fail to bud or divide while drug is present. Recovery after drug removal and subsequent colony formation would distinguish reversible arrest from killing. The experiment also does not identify which actin-dependent process first becomes limiting; matched measurements of trafficking, budding and division would be needed for that ordering.
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