Linear representation of the constructs used in this work. a) At the top of the figure the p42d repABC operon is shown. Grey arrows represent genes encoding the partitioning proteins and parS and the grey ellipse represents the centromeric-like region parS. A white arrow shows the relative position of the gene encoding RepC, a protein essential for replication. Dashed arrow represents a gene encoding a small antisense RNA that modulates repC expression. Boxed P1 and P2, indicate the position and transcription directions of the promoters found within the repABC operon. Brackets indicate regions involved in plasmid incompatibility. Below, graphic representation of the genetic elements present in each one of the constructs used in this work, using the same symbols than above. Square filled with horizontal lines shows the relative position of pLac, a constitutive promoter in Rhizobium. b) A magnification of the repC gene and repC gene fragments present in the constructs, including the genetic elements introduced by us: white vertical rectangle represent a Shine-Dalgarno (SD) sequence, while the black vertical rectangle shows the initiation codon. Crossed rectangle indicates that the SD sequence was eliminated in that particular construction. Crosses within the white arrows, marked with SphI or BglII, indicate that inserts of those constructs possess a frame-shift mutation in that specific point. Construct names are listed in the left column and their replication capabilities in strains CFNX101 and CFNX107 are listed in the columns in the right: (+) indicates that the construct is capable of autonomous replication and (-) that the construct does not have this property.