Abstract
The biofilm matrix of the rhizospheric bacterium Pseudomonas putida consists mainly of a proteinaceous component. The two largest P. putida proteins, adhesins LapA and LapF, are involved in biofilm development but prevail in different developmental stages of the biofilm matrix. LapA is abundant in the initial stage of biofilm formation whereas LapF is found in the mature biofilm. Although the transcriptional regulation of the adhesins is not exhaustively studied, some factors that can be involved in their regulation have been described. For example, RpoS, the major stress response sigma factor, activates, and Fis represses LapF expression. This study focused on the LapF expression control by Fis. Indeed, using DNase I footprint analysis a Fis binding site Fis-F2 was located 150 bp upstream of the lapF gene coding sequence. The mapped 5′ end of the lapF mRNA localized the promoter to the same region, overlapping with the Fis binding site Fis-F2. Monitoring the lapF promoter activity by a β-galactosidase assay revealed that Fis overexpression causes a 4-fold decrease in the transcriptional activity. Furthermore, mutations that diminished Fis binding to the Fis-F2 site abolished the repression of the lapF promoter. Thus, these data suggest that Fis is involved in the biofilm regulation via repression of LapF expression.
Highlights
The biofilm matrix consists of bacterial metabolites excreted from the cells into the medium
The two largest proteins in P. putida, the adhesins LapA and LapF, are known to be crucial for P. putida’s biofilm formation [5,6,7,8]. These adhesins are involved in biofilm development and prevail in different developmental stages of the biofilm matrix – LapA is necessary at the beginning of biofilm formation and LapF in mature biofilm [5, 7,8,9,10]
E. coli was incubated at 37 ̊C and P. putida at 30 ̊C
Summary
The biofilm matrix consists of bacterial metabolites excreted from the cells into the medium. The involvement of Fis in biofilm formation has been described in some studies [18,19,20,21,22], no one has shown the direct transcription regulation of adhesin genes in P. putida by Fis. In this study, the 59 end of the lapF mRNA is mapped, and the location of the lapF promoter is determined.
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