Western blot analyses of a 10% sodium dodecyl sulfate-polyacrylamide gel using the rabbit polyclonal anti-Esp serum. The Western blot shows growth culture-dependent expression of Esp in one esp-negative E. faecium strain (E135) and six esp+ E. faecium strains (E155, E470, E745, E1165, E1172, and E1176). Bacteria listed were grown on SRA for 72 h at 21°C under aerobic conditions (lanes A), 18 h at 37°C under aerobic conditions (lanes B), or 18 h at 37°C under anaerobic conditions (lanes C). Numbers to the left of the gel are molecular weights (in thousands).