Heterologous expression of LVIS552 and LVIS553 in L. brevis and B. subtilis. A, L. brevis cells were grown with increasing concentrations of novobiocin in the presence (closed squares) or absence (closed circles) of LVIS552-LVIS553 cloned in pRV610. B, growth of B. subtilis with a chromosomal insertion of LVIS552-LVIS553 in the sacA locus (closed squares), empty controls (kanamycin cassette in the sacA locus, closed circles), and LVIS552-LVIS553 (K9A) mutant (open squares). Growth was expressed as a percentage of the OD of cells grown without novobiocin.