Selection of Ampicillin‑Resistant Transformants: Isolates colonies of E. coli harboring β‑lactamase–encoding plasmids on LB Lennox (1.0% Tryptone, 0.5% Yeast Extract, 0.5% Sodium Chloride, 1.5% Agar) with 100 µg/mL ampicillin.

Plasmid Maintenance and Propagation: Maintains selection pressure to preserve plasmids in recombinant E. coli clones during streaking and passaging.

Blue‑White Screening (with X‑gal/IPTG): Enables α‑complementation screening on LB/Amp plates supplemented with X‑gal and IPTG to identify inserts in E. coli.

Colony Isolation and Purification: Allows single‑colony isolation from mixed or transformed cultures for clonal purification of recombinant E. coli.

Colony PCR Template Preparation: Provides selective colonies for rapid PCR screening of inserts or constructs directly from E. coli colonies.

Transformation Efficiency and CFU Enumeration: Quantifies colony‑forming units and transformation success on selective LB Lennox agar with ampicillin.

Pre‑Screening Expression Constructs: Screens recombinant clones on solid media prior to liquid culture expression in E. coli.

Glycerol Stock Seed Colonies: Generates verified single colonies for downstream starter cultures and long‑term storage of engineered E. coli strains.

Contamination Control: Differentiates ampicillin‑resistant recombinant E. coli from non‑resistant contaminants during strain maintenance.