Biofilms are widely present in aquatic engineering systems, where they are mainly implicated in biofouling and corrosion. Biofilm causes nosocomial infections by forming a persistent growth in catheters and other body implants and medical devices; they also increase drug resistance and dental caries (Donlan, 2001). On the other hand, the development of biofilm followed by biofouling in the cooling water system causes severe blockage of refrigerant piping in power plants, resulting in increased load on pumps, microbial-induced corrosion, and substantial economic losses (Boffardi, 2005; Flemming, 2002; Oliveira, et al., 1993 and Rao et al. In waste treatment systems such as trickling filters, wet biofilms are used to catalyze the transformations of pollutants (Wyndham, 1995). extremely diverse, as is their lifestyle and adaptation to survive in any environment (Staley et al, 1997). they use their pili or flagella to establish primary attachment (Virji et al. 1993). The present work studied the role of a surface protein (Bap) in S. aureus in establishing biofilm on the glass surface and topological changes. in response to Ca2+ concentration from 1mM to 20mM on biofilm morphology. Previous work by Arrizubieta et al. (2004) demonstrated that Bap expression is not affected by the presence of Ca2+. We provide insight into changes in surface protein-mediated growth in the presence of various Ca2+ concentrations. Calcium is an environmental variable that influences biofilm formation of some bacteria (Geesey et al. 2000; Patruchan et al. 2005). In a previous Arrizu report...... middle of paper ......erent environment containing variable concentrations of calcium. Conclusions: From this investigation we have established the following salient points; (1) Bap-mediated biofilm development in S. aureus V329 is inhibited  5 mM calcium (2) Other bap negative strains of S. aureus, SA7 and SA33 show no inhibition due to the presence of calcium even up to 50 mm. (3) Structurally similar BapA harboring A. baumannii showed no inhibition in biofilm formation in response to calcium. (4) The CSLM study demonstrated that varying Ca 2+ concentrations significantly affected biofilm architecture and topology. The CSLM study also shows that calcium chelation using EDTA can reverse the effect of calcium on biofilm development. (5) This study also specifies that the presence of the EF hand motif in Bap makes the V329 strain sensitive to the presence of Ca 2+ in the environment.