Selection of Erythromycin-Resistant Colonies: Isolates colonies carrying erm resistance markers on TSA (1.5% Tryptone, 0.5% Soytone, 0.5% NaCl, 2.0% Agar) with 10 µg/mL erythromycin.

Plasmid Maintenance in Gram-Positives: Sustains plasmids with erm selectable markers in Staphylococcus aureus, Bacillus subtilis, Lactococcus lactis, Enterococcus faecalis, and Streptococcus pneumoniae.

Screening Transformants/Transductants: Selects successful genetic transformants or phage transductants carrying erm genes on solid medium.

Conjugation/Transposition Selection: Recovers transconjugants and transposon insertion mutants under erythromycin pressure.

Counterselection in Mixed Cultures: Suppresses erythromycin-sensitive background flora to enrich target Erm^R strains.

Clonal Isolation and Maintenance: Streaks for single colonies and routine passaging of Erm^R Gram-positive strains.

Verification of Genetic Integrations: Confirms chromosomal integrations or knock-ins using erm as a selectable marker.

Qualitative Susceptibility Screening: Rapidly differentiates erythromycin-resistant versus sensitive isolates on TSA.

Phage and CRISPR Workflows: Applies selection after phage delivery or CRISPR editing steps in Erm^R Gram-positives.

Process and QC Microbiology: Monitors and tracks engineered Erm^R production or starter strains in industrial settings.