Application of mobilization gene promoter for heterologous expression and curing of plasmid pSMA23

Abstract

Lactobacilli have been recognized as key members of the group of probiotic bacteria by virtue of expressing a wide spectrum of physiological functions beneficial to human health. Genetic modification of this genus requires the availability of tools for gene expression like promoter and suitable host vector systems. In the context, plasmid pSMA23 was cured from its native host <em>Lactobacillus casei</em> A23 by electroporation with a construct based on the pSMA23 replicon. Cured strain A23 can be employed as host for vectors or constructs based on the replicon of pSMA23 and for heterologous expression of genes. The promoter less gene <em>cat194</em> coding for chloramphenicol resistance was cloned under the control of the putative mobilisation gene promoter present on the native plasmid pSMA23 of <em>Lactobacillus casei </em>A23. Constructs were electroporated into <em>Lactobacillus </em><em>casei </em>LK1 and transformants were obtained on media containing chloramphenicol, indicating expression of the <em>cat194</em> gene. The putative promoter is thus active and can be recruited for gene expression.