A recombinant gram-negative bacterial cell comprising one or more of the following mutated protease genes: a. a mutated Tsp gene, wherein the mutated Tsp gene encodes a Tsp protein having reduced protease activity or is a knockout mutated Tsp gene; b. a mutated ptr gene, wherein the mutated ptr gene encodes a Protease III protein having reduced protease activity or is a knockout mutated ptr gene; and c. a mutated DegP gene encoding a DegP protein having chaperone activity and reduced protease activity; wherein the cell is isogenic to a wild-type bacterial cell except for the mutated Tsp gene and/or mutated ptr gene and/or mutated Deg P gene and optionally a polynucleotide sequence encoding a protein of interest.
