Biofilm is a complex aggregation of microorganisms, principally bacteria, associated with their extracellular polymers, and surface attached. Many bacteria, mainly saprophytes, but also some oportunistic human pathogens, live in a water sypplying system. Depending on water quality and other factors, these bacteria are able to form biofilms. The formed biofilm is usually resistant to traditional supply system treating methods, including disinfection. The aim of this study is to make a contribution to the knowledge about bacteria Pseudomonas aeroginosa in biofilm structure. By understanding biofilms, wrong interpretation of microbiological results in water supply system samples analyses could be avoided.

There was carried out microbiological analysis of five bottled water of manufacturers from Serbia. Bacteriological quality was estimated using important parameter-aerobic mesophylic bacteria. Two nutrient media were used: standard (PCA) and low nutrient R2A. Plates were incubated at two temperatures (37 deg C and 22 deg C) during 24 hours, 48 hours, 3 days and 5 days. Results show that this group of bacteria is very abudant in bottled waters and their number depends on water types and manufacturers. Moreover, water from different bottles of the same manufacturer has different microbiological quality. Used media, temperatures and period of incubation also have influence on results and R2A medium gives higher values of aerobic mesophylic bacteria.