Transformation efficiencies of UA159 and isogenic lytS and lrg mutants. To compare the ability of UA159 and its isogenic lytS, lrgA, lrgB, and lrgAB mutants to take up exogenously-added plasmid DNA, a quantitative competence assay was performed on n = 4-6 biological replicates of each strain as described in Methods . Plasmid pAT28 [encoding spectinomycin resistance;  was used to assess transformation efficiency in UA159, lytS, lrgB, and lrgAB mutants. Because the lrgA mutant was generated with a spectinomycin-resistance cassette , plasmid pORi23 [encoding erythromycin resistance; ] was used to assess transformation efficiency in UA159 and lrgA mutant. Transformation efficiencies (Y axis) in the presence (grey bars) and absence (white bars) of CSP are expressed as the percentage of transformants (CFU/ml on BHI + selective antibiotic) among total viable cells (CFU/ml on BHI). Error bars represent SEM. Brackets with P values denote statistically-significant differences between two samples (Mann–Whitney Rank Sum Test).