TABLE 1.

RTX toxin activity and protease activity in supernatant fluids of various V. cholerae strainsa

StrainRelevant genotype (reference)RTX activitybProtease activityc
LogStatLogStat
N16961N16961 wild type (12)+++ND0.22 ± 0.01
KFV43N16961ΔhapA (12)+++ND0.085 ± 0.001
KFV18RN16961pilD::km (12)+++NDND
KFV44N16961pilD::kmΔhapA (12)+++NDND
E7946E7946 wild type (27)0.21 ± 0.0034.5 ± 0.77
E7946mpc Multiple protease control (40)+++ND0.16 ± 0.01
Bah1E7946Δcore (24)0.14 ± 0.025.27 ± 0.18
BMV5Bah1ΔtoxS (this study)++ND0.74 ± 0.07
BMV6BMV5ΔhapA (this study)+++ND0.15 ± 0.08
Bah1PBah1ΔhapA (13)++0.02 ± 0.010.41 ± 0.01
  • a Log, log phase (A 600 = 0.4); Stat, stationary phase (overnight cultures).

  • b RTX activity assayed as actin cross-linking as shown in Fig. 2. −, only monomer; +, only dimer; ++, cross-link to trimer; +++, cross-link to tetramer and higher.

  • c Protease activity determined by azocasein assay and expressed as A 366/h. ND, not detectable. The values reported for total protease activity are averages and standard deviations of at least three azocasein digestion assays.