Leriche et al. [19] have described the protection of certain bacterial strains by other strains within a mixed biofilm system. We therefore investigated the potential for a “”non biofilm-forming”" isolate (isolate 80) to be incorporated into the biofilm produced by isolate 17, a strong biofilm producer and showed that not only can an established biofilm of P. aeruginosa assist in the attachment and colonisation of another isolate, but also that the two P. aeruginosa isolates became integrated in a mixed biofilm as shown in cross section CSLM images (Fig. 5). In the mixed

biofilm scenario in vitro, the CF P. aeruginosa biofilm could consist of many different isolates, some of which are unable to form biofilms themselves yet can colonise an already established biofilm. Adaptability CH5424802 is the key to successful colonisation of an environmental niche and in the field of infectious disease, it is widely accepted that BIRB 796 purchase a pathogen will normally have more than one way of exerting a pathogenic effect. Many pathogens, therefore, have multiple adhesion mechanisms allowing attachment to, for example, epithelial cells [46]. We contend that the physiological mechanisms involved in biofilm formation should be considered in a similar manner,

in that a deficiency in one phenotypic aspect of biofilm formation may be compensated for by other genetic and phenotypic factors. Conclusions Motility makes a positive contribution to biofilm formation in CF isolates of P. aeruginosa, but is not an absolute requirement. It is clear that CF isolates with differing motility phenotypes can act synergistically to form a mixed biofilm. This could give an advantage to bacterial communities as they would possess a greater repertoire of genetic ability, thus allowing them to adapt to different challenges e.g. antibiotic chemotherapy,

host inflammatory responses, etc. Acknowledgements ED was in receipt of a Vice Chancellor’s Research Scholarship from the University of Ulster. ED also gratefully acknowledges receipt of a Society for General Microbiology “”President’s Fund”" award for travel to the CBE, MT, USA. Thanks are due to Dr Graham Hogg (Belfast City Hospital) for providing the P. aeruginosa strains used in this study Ureohydrolase to and Dr Steven Lowry of the University of Ulster for his assistance with SEM. We thank Prof. Phil Stewart for the hospitality in his laboratory at The Centre for Biofilm Engineering, MT and Ms Betsy Pitts for providing training and assistance with CSLM studies. References 1. Lawrence JR, Horber DR, Hoyle BD, Costerton JW, Caldwell DE: Optical sectioning of microbial biofilms. J Bacteriol 1991, 173:6558–6567.PubMed 2. Nickel JC, Costerton JW: Bacterial localisation in antibiotic-refractory chronic bacterial prostatitis. Prostate 1993, 23:107–114.