This may reflect not only the absence of FDC, which contribute to the bright staining of B-cell follicles in WT mice spleen, but also downregulation of CLU in other stromal cell types in the absence of LTbR signal. Adherent bacteria profoundly differ from planktonic bacteria in physiology and gene expression. From this collective surfaceattached life mode, the bacteria gain significant adaptive advantages and exhibit increased resistance to many biocides. This adhesion-induced physiological shift was suggested very early on by scientists studying bacterial populations in aqueous receptacles and has since been confirmed on the basis of molecular biology data. Recently, abundant information on gene expression and metabolic pathway alterations in established biofilms has emerged due to the increasing spread of molecular genetics. However, the mechanisms of such a transition are not known. The data, obtained on a several hour or day time scale, depict interfering biochemical cascades upor downregulated in the surface-attached mode of growth compared to the free-floating mode. This reinforces the idea of a surface-attached specific mode of life, but does not enable distinguishing triggering events from further Tramiprosate developmental stages that drive biological changes on surfaces. In particular, the respective contributions of the various factors prevailing in biofilms ��actual cell surface contact, cell-cell interactions, secreted soluble molecules or extracellular matrix synthesis, together with modifications in the physical and chemical Shz 1 environment due to confinement of cells in a 3D viscoelastic architecture �� have not been identified, and their causality remains elusive. In this paper, we focused on the early stage of cell-surface contact formation. Evidence of a direct cell response upon initial adhesion is scarce. Using reporter gene technology and microscope observation in Pseudomonas aeruginosa individual cells, Davies and Geesey concluded that attachment of the cell to a glass surface induced algC upregulation as early as the first 15 min of contact. In addition, Otto and Silhavy described increased expression of Cpx-regulated genes upon 1 h contact of Escherichia coli with artificial surfaces as compared to planktonic cells maintained in suspension; surprisingly, this regulation was observed with stationary phase cells in contact with a hydrophobic surface only. Lately, Li and co-workers showed, in Caulobacter crescentus, that formation of physical contact between the bacterium and an artificial surface triggered ����just-in-time���� adhesin production.