Single-vector Type I vectors

A production strain bacterial cell comprising a nucleic acid vector for introduction into a target bacterial host cell for expression of Type I Cas3 and Cascade proteins in the target bacterial host cell, the vector comprising a first nucleotide sequence encoding a Type I Cas3 and a second nucleotide sequence encoding one or more cognate Cascade proteins, wherein the first nucleotide sequence is under the control of a promoter for controlling the expression of Type I Cas3 in the target bacterial host cell, wherein the promoter has a strength that is weaker than the Anderson Score strength of promoter BBa_J23108,

• wherein the nucleic acid vector further comprises:
• (i) a CRISPR array for producing a crRNA in the target bacterial host cell;
• or (ii) a nucleotide sequence encoding a guide RNA (gRNA), wherein the crRNA or gRNA comprises a spacer sequence complementary to a target sequence of the target bacterial host cell, and
• wherein the production strain bacterial cell does not comprise a crRNA or gRNA operable with the Cas3 to target and cut a chromosomal sequence of the production strain cell.