A composition comprising at least 4 different types of transduction particles, wherein each of said particles comprises a nucleic acid and said particles are capable of contacting E coli cells and introducing therein the nucleic acid, wherein (a) said nucleic acid of each particle comprises a nucleotide sequence encoding a product of interest, wherein the nucleic acid is capable of expressing the POI in an E coli cell; and wherein the POI comprises: (i) a Cas nuclease for targeting and cutting the DNA of the E coli cell, thereby modifying or killing the cell; and (ii) at least one crRNA or guide RNA each comprising a spacer sequence that is complementary to a protospacer sequence comprised by a gene selected from B2 phylogroup E coli genes fimH, bolA, rpoH, lptA and murA and each of which is operable with the Cas nuclease for DNA targeting in the E coli cells; (b) each particle comprises: (iii) an adhesion moiety for recognising and binding to a cognate moiety selected from a LPS and Tsx displayed on the surface of E coli cells; and (iv) a phage capsid containing the nucleic acid; and (c) said at least 4 different types of transduction particles comprises A: particles which comprise a LPS adhesion moiety and a LamB adhesion moiety; B: particles which comprise a LPS adhesion moiety and a Tsx adhesion moiety; and C: particles which comprise a Tsx adhesion moiety but are devoid of LamB and LPS adhesion moieties; and wherein the particles of the composition target all of E coli genes fimH, bolA, rpoH, lptA and murA. (a) said nucleic acid of each particle comprises a nucleotide sequence encoding a product of interest, wherein the nucleic acid is capable of expressing the POI in an E coli cell; and wherein the POI comprises: (i) a Cas nuclease for targeting and cutting the DNA of the E coli cell, thereby modifying or killing the cell; and (ii) at least one crRNA or guide RNA each comprising a spacer sequence that is complementary to a protospacer sequence comprised by a gene selected from B2 phylogroup E coli genes fimH, bolA, rpoH, lptA and murA and each of which is operable with the Cas nuclease for DNA targeting in the E coli cells; (i) a Cas nuclease for targeting and cutting the DNA of the E coli cell, thereby modifying or killing the cell; and (ii) at least one crRNA or guide RNA each comprising a spacer sequence that is complementary to a protospacer sequence comprised by a gene selected from B2 phylogroup E coli genes fimH, bolA, rpoH, lptA and murA and each of which is operable with the Cas nuclease for DNA targeting in the E coli cells; (b) each particle comprises: (iii) an adhesion moiety for recognising and binding to a cognate moiety selected from a LPS and Tsx displayed on the surface of E coli cells; and (iv) a phage capsid containing the nucleic acid; and (iii) an adhesion moiety for recognising and binding to a cognate moiety selected from a LPS and Tsx displayed on the surface of E coli cells; and (iv) a phage capsid containing the nucleic acid; and (c) said at least 4 different types of transduction particles comprises A: particles which comprise a LPS adhesion moiety and a LamB adhesion moiety; B: particles which comprise a LPS adhesion moiety and a Tsx adhesion moiety; and C: particles which comprise a Tsx adhesion moiety but are devoid of LamB and LPS adhesion moieties; and wherein the particles of the composition target all of E coli genes fimH, bolA, rpoH, lptA and murA. A: particles which comprise a LPS adhesion moiety and a LamB adhesion moiety; B: particles which comprise a LPS adhesion moiety and a Tsx adhesion moiety; and C: particles which comprise a Tsx adhesion moiety but are devoid of LamB and LPS adhesion moieties;