To this end, the collection of ~40.000 KmR colonies derived from P. putida MAD1 plated on M9-citrate with kanamycin and exposed to m-xylene was examined for the appearance of paler blue tones or unusual patterns of Xgal in the otherwise dark blue of the control colonies that peak at the colony centre. Seven of these (Figure 3D and Table S3 of Additional File 1) were chosen for further

analysis. The sequence of the corresponding sites of insertion revealed at least two types of genes that influenced the outcome of anti-EGFR antibody the Pu-lacZ reporter. One group is constituted by an insertion in dnaJ, which appears to downregulate Pu (Figure 3D). DnaJ is a heat-shock protein that stimulates the ATPase activity of DnaK [38] and is perhaps involved in the pathway for proper folding of σ54 (RpoN; [39]). A similar Xgal distribution pattern is observed when the PP1841 gene is disrupted (Figure 3D). Yet, the most unusual phenotype of the Pu-lacZ fusion carried by P. putida MAD1 appeared in an insertion

within the intergenic region between cstA, a gene, which encodes a carbon-stress response protein [40], and PP4642, a type IV pilus assembly gene. In these cases (Figure 3D), the colonies displayed a double-ring distribution of the dye that suggested an influence of either or both of these proteins in adjusting the physiological control of Pu activity [37]. Other interesting phenotypes were produced by mutations in cysD and cysNC genes, the loss of which produce small, slow-growing colonies with a distinct RG7422 supplier fisheye distribution of Xgal. These mutations are expected to bring about a general deficiency of cysteine Methocarbamol [41], which could directly or indirectly affect transcriptional activity (Additional File 1, Table S3). Needless to say, these are preliminary observations that require further examination (see other insertions in Table S3 of Additional File 1). In the meantime, these results illustrate the power of the genetic tool employed for tackling regulatory phenomena. Survey and localization of

highly-expressed proteins in Pseudomonas putida Although the literature reports many systems for generating fluorescent fusion proteins [42, 43] we exploited the layout of the pBAM1 plasmid for constructing a variant able to produce in vivo random insertions of the GFP sequence in chromosomal genes. We reasoned that if a promoterless and leaderless GFP inserts in a gene in the right orientation and in the correct frame we should be able to detect green colonies when insertion occurs either in non essential genes expressed at very high rates or in their permissive termini (note that the final GFP fusions are single-copy). To explore this notion, we constructed a pBAM1 derivative in which the PvuII insert (i.e. the whole mini-transposon part) was replaced by a synthetic DNA with a number of new features.