Spot tests of co-transformants of either Bd0367 (DgcA; GGDEF protein) response regulator domain or Bd3125 (CdgA; a degenerate GGDEF protein likely involved in c-di-GMP binding and signalling) with full length Bd1971, or the N-terminal (1-145), or C-terminal (145-400) portions of Bd1971 in either pUT18c or pKT25 as indicated. Positive control was co-transformants with pUT18c-zip and pKT25-zip, negative control was the empty vectors. The co-transformants were plated on LB-X-Gal medium with positive interaction resulting in blue colouration, which can be seen for all of the interactions in both plasmid combinations, but not for the negative control. Images are representative of at least 4 independent experiments. 