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International audience; Biofilms are microbial communities characterized by three-dimensional growth resulting from the ability of individual cells to adhere to each other as well as to produce an extracellular matrix that ensures biofilm physical cohesion. Numerous bacteria produce cellulose as a biofilm matrix polymer, a property relying on the expression of bacterial cellulose synthesis (Bcs) proteins and their post-translational activation upon binding of cyclic di-guanosine mono-phosphate second messenger (c-di-GMP) produced by diguanylate cyclases. In Escherichia coli and other Enterobacteriaceae, two genes of unknown function, yhjR and yhjQ, are located upstream of the bcs genes. Here, we show that yhjQ, but not yhjR, is essential for cellulose biosynthesis; it has therefore been renamed bcsQ. Using a green fluorescent protein (GFP) fusion approach, we demonstrate that BcsQ, a MinD homologue, displays a polar localization and that cell-to-cell adhesion is initiated through production of cellulose at the BcsQ-labelled pole. Although we did not detect a similar localization for other Bcs proteins, immunogold labelling of cellulose itself at the pole of individual bacteria indicates the localized activity of the cellulose biosynthesis apparatus. These results therefore suggest that BcsQ could participate in spatial restriction of cellulose biosynthesis activity in Enterobacteriaceae.

Despite the economic and sanitary problems caused by harmful biofilms, biofilms are nonetheless used empirically in industrial environmental and bioremediation processes and may be of potential use in medical settings for interfering with pathogen development. Escherichia coli is one of the bacteria with which biofilm formation has been studied in great detail, and it is especially appreciated for biotechnology applications because of its genetic amenability. Here we describe the development of two new genetic tools enabling the constitutive and inducible expression of any gene or operon of interest at its native locus. In addition to providing valuable tools for complementation and overexpression experiments, these two compact genetic cassettes were used to modulate the biofilm formation capacities of E. coli by taking control of two biofilm-promoting factors, autotransported antigen 43 adhesin and the bscABZC cellulose operon. The modulation of the biofilm formation capacities of E. coli or those of other bacteria capable of being genetically manipulated may be of use both for reducing and for improving the impact of biofilms in a number of industrial and medical applications.