**5.5 Properties of the cells**

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 by impeding the mass transport of antibiotics through the biofilm, which might be by binding directly to these agents [1]. EPS formation is an essential part of biofilm formation as studies on *Staphylococcus epidermidis* have shown that if genes responsible for the synthesis of EPS matrix are inactivated then bacteria lose the ability to form biofilm [2].

### **5.6 Environmental factors**

Different environmental factors affect the biofilm formation; listed below:

### *5.6.1 Availability of certain nutrients*

It has been shown by studies on *Listeria monocytogenes* that an optimum level of phosphate is very important for biofilm formation and gets stimulated by the presence of carbohydrates mannose and trehalose.

### *5.6.2 Presence of oxygen*

Presence of oxygen regulates Biofilm formation in *Escherichia coli*. In the absence of sufficient oxygen supply biofilm does not form as bacteria could not adhere to the substrate surface.

### *5.6.3 Environmental pH*

Environmental pH effects were observed by studying on *Vibrio cholerae*. Optimal pH for multiplication of *V. cholerae* is 8.2 and below pH 7 i.e., in acidic environment the bacteria lose their ability to form biofilm as they lose mobility.

On the other hand, bacteria like *S. epidermidis* and *E. coli* do not need an alkaline environment for multiplying hence they easily form a biofilm on urethral catheters where urine pH is acidic.

### *5.6.4 Temperature*

When temperature was kept high, *L. monocytogenes* did not form biofilm as the bacteria wasn't able to adhere itself to the substrate surface [2].
