TABLE 4.

Dependence of esp expression on lera

Strain 86-24 genotypeβ-Galactosidase activity/A600% changeb
hha+ ler+ esp::lac29.7 ± 3.60
Δhha ler+ esp::lac1,134 ± 48.4+3,818
Δhha Δler esp::lac59.4 ± 6.3+200
Δler hha+ esp::lac29.2 ± 4.2−1.69
  • a Effect of ler on the expression of esp operon was monitored by the determination of β-galactosidase activity of a chromosomal esp::lac fusion in 86-24 and its derivatives deleted either of ler or hha or both ler and hha. Strains were cultured in LB broth and samples for monitoring β-galactosidase activity and A600 were taken after 270 min of growth.

  • b See Table 3, footnote c. The assay variability was within 4 to 15% of the mean of three independent measurements. High variability was normally seen in samples expressing very low β-galactosidase activity.