FIG. 3.

Phenotypes of an fda mutant of P. putida MAD2. The chromosomal context of the fda gene encoding fructose-1,6-bisaldolase in this strain is shown at the top. Adjacent ORFs appear to determine unrelated functions: PP4961 is a putative lipoprotein, PP4959 encodes a response regulator, and PP4958 is a conserved protein whose function is unknown. The fda gene is placed at considerable distances (104 and 216 bp) from adjacent genes upstream and downstream, and it is thus likely to form a single transcriptional unit. The plate assays at the lower left show the growth of the fda mutant with glucose and fructose as the only C sources with the wild-type (wt) P. putida MAD2 strain as a positive control and a fruB mutant unable to consume fructose as a negative control (Fig. 2). For the experiment shown to the lower right, Pu-lacZ reporter strain P. putida MAD2 and its fda derivative were subjected to a carbon Pu inhibition test as explained in Materials and Methods and Fig. 1. Note that fructose becomes a repressive C source of this promoter in the fda mutant. β-gal, β-galactosidase; U. Miller, Miller units.