Table 1. Temperature‐dependent expression of virF–lacZ fusions
Strains/plasmidsβ‐Galactosidase activitya
Expressed at 30°C37°CExpression ratio (37/30°C)
MC4100 (wt)/pFABlac112833 (±15%)4180 (±10%)5.02
HN4104 (hns118)/pFABlac1127537 (±8%)5781 (±9%)0.77
HN4122 (wt)/pFABlac112542 (±18%)2162 (±7%)3.99
HN4124 (hns2)/pFABlac1122005 (±1%)1970 (±1%)0.98
HN4122 (wt)/pFBlac21051 (±9%)1703 (±10%)1.62
HN4124 (hns2)/pFBlac21929 (±6%)1918 (±4%)0.99
aUnits of β‐galactosidase are calculated according to Miller (1992). The results represent the average of at least four independent experiments, and standard deviation values expressed as a percentage are reported in parentheses. The plasmid copy number, determined as previously described (Prosseda et al., 1998), does not exhibit a significant difference between wild‐type and hns mutants strains.