Fig. 1

Milestones in construction of unstable BHR vector. Circular maps of intermediate (a, b and c) and final vectors (d, e and f) are drawn to scale. Only intact orfs are indicated. Unique or double restriction sites important for cloning are shown, those described in the text are in bold. T₁ marks the divergent transcription terminator sequence T _pro /T _lyz of P1 prophage [49]