Observations of cell cluster hollowing in Staphylococcus epidermidis biofilms

Abstract

Microbial biofilm formation appears to involve complex multicellular behaviours. For example, some bacteria exhibit extensive twitching and swarming motility after association with a surface. These forms of motility appear to be coordinated and to contribute to the spatial organization of biofilm structures (O’Toole and Kolter 1998; Klausen et al. 2003). Another intriguing phenomenon is the appearance of hollow interiors in biofilm cell clusters. Such hollowing seems to occur in the later stages of biofilm development. Hollow biofilm structures have been described for Pseudomonas aeruginosa (Sauer et al. 2002; Webb et al. 2003; Hunt et al. 2004; Parsek and Fuqua 2004; Stapper et al. 2004), Pseudomonas putida (Tolker-Nielsen et al. 2000), Pseudoalteromonas tunicate (Mai-Prochnow et al. 2004) and Actinobacillus actinomycetemcomitans (Kaplan et al. 2003) biofilms. Particularly, striking are movies in which motile cells can be seen seething in the centre of a cell cluster containing many immotile cells (Tolker-Nielsen et al. 2000; Hunt et al. 2004). Here, we report the direct microscopic observation, by a suite of techniques, of hollow cell clusters in Staphylococcus epidermidis biofilms.