Abstract: The invention relates to a cloning vector suited for the souring bacteria of dairy industries, which cloning vector is based on a 1.7 kb ClaI fragment of the Streptococcus lactis cryptic plasmid pSH71. Therein are inserted a chloramphenicol resistance gene from the Streptococcus sanguis plasmid pGB301 and an erythromycin resistance gene from the Staphylococcus aureus plasmid pE194, a 0.35 kb fragment from the Escherichia coli plasmis pBR322 being inserted therebetween. The size of the cloning vector is 5.0 kb. The cloning vector enables the use of "forced cloning" methods. It possesses a wide host spectrum (group N streptococci, Escherichia coli, Bacillus subtilis), and can be applied for improving the souring properties of the group N streptococci and for the preparation of foreign proteins in these bacteria or other hosts.