**5. Factors affecting biofilm formation**

A number of factors such as substratum effects, hydrodynamics and various properties of cell surface play an important role in microbial attachment [1].

### **5.1 Substratum effects**

As the surface roughness increases microbial colonization increases because as the roughness increases, surface area increases and shear forces get diminished. And considering extent and rate of attachment, it has been seen that microorganisms get attached to more rapidly to hydrophobic and nonpolar surfaces as Teflon and other plastics rather than to glass and other materials having hydrophilic properties.

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*Microbial Biofilms*

**5.3 Hydrodynamics**

detachment of these cells [1].

glass surfaces.

**5.5 Properties of the cells**

**5.4 Characteristics of the aqueous medium**

*DOI: http://dx.doi.org/10.5772/intechopen.90790*

**5.2 Conditioning films forming on the substratum**

within hours of exposure to this pellicle conditioned surface.

When a material surface gets exposed to any aqueous medium, it gets immediately coated with polymers from that surface or become conditioned. The coating or film is found to be organic in nature formed within minutes of exposure. The nature of these films is found to be quite different for surfaces exposed in the human host. As an example, "acquired pellicle," a proteinaceous conditioning film, develops on tooth enamel surface. A pellicle is composed of glycoprotein, lysozymes, phosphoproteins, albumin, lipids and gingival crevice fluid. Oral cavity bacteria get adhered

The hydrodynamic flow layer is the zone of negligible flow which is found at the immediately adjacent to the substratum/liquid interface. The flow velocity of this zone is negligible and its thickness is inversely proportional to the linear velocity. Substantial mixing or turbulence is the main characteristics shown by the region outside the boundary layer. The hydrodynamic boundary layer can considerably affect the interaction between cells and substratum. The velocity characteristic of the liquid governs the association of cells with the submerged surfaces. At, very low linear velocities, the cells must navigate through the hydrodynamic boundary layer, and cell size and cell motility govern its association with the surface. The boundary layer decreases, as the velocity increases and cells will be exposed to progressively larger turbulence and mixing. Therefore, higher linear velocities would be supposed to form a more rapid association with the surface, at least until velocities become high enough to apply abundant shear forces on the attaching cells, that results in

Characteristics of the aqueous medium such as temperature, pH, nutrient level and ionic strength possibly play an important role in attachment of microbes with the substratum. As an example, it has been found that the attachment of *Pseudomonas fluorescens* to glass surface is affected by an increase in the concentration of several cations (sodium, calcium, lanthanum, ferric iron), perhaps by reducing the repulsive forces between the negatively charged bacterial cells and the

The rate and extent of adherence of microbes depends on the properties of cells like cell surface hydrophobicity, as hydrophobic interactions tend to increase with an increasing nonpolar nature of one or both involved surfaces and adhesion increases with increase in hydrophobicity*,* presence of fimbriae and flagella as fimbriae contribute to cell surface hydrophobicity probably by overcoming the initial electrostatic repulsion barrier that exists between the cell and substratum and production of EPS. EPS might be hydrophobic, although mostly they are both hydrophilic and hydrophobic. Numerous bacterial EPS have the backbone of 1,3- or 1,4-β-linked hexose residues and tend to be less deformable, more rigid and inadequately soluble or insoluble in specific cases although other EPS molecules may be water soluble. Researches also showed that different organisms produce different amounts of EPS and the amount of EPS increases with age of the biofilm. Antimicrobial resistance properties in the biofilm are possibly mediated by the EPS
