A CRYPTIC PLASMID PBL1 FROM BREVIBACTERIUM-LACTOFERMENTUM CAUSES GROWTH-INHIBITION AND FILAMENTATION IN ESCHERICHIA-COLI

A shuttle vector composed of pBL1, a 4.46-kb cryptic plasmid from cory neform bacterium Brevibacterium lactofermentum, and Escherichia coli v ector pHSG298 was found to inhibit growth and cause cell filamentation in E. coli. After construction of several deletions of pBL1, a 1.23-k b AccI-HindIII fragment was found responsible. DNA sequence analysis s howed that this fragment contained a 726-bp-long open reading frame (O RF3), encoding a protein with 242 amino acid residues. Corresponding t o ORF3, a 28-kDa protein was detected in an in vitro protein synthesis system. ORF3 was dispensable for the stable maintenance of pBL1 in co ryneform bacteria. (C) 1996 Academic Press, Inc.