Magnetic Particle Induction and Its Importance in Biofilm Research

Since the mid-twentieth century scientists have been aware that aquatic bacteria are more abundant as biofilms on solid surfaces than as suspended free cells (ZoBell, 1943). The last few decades have seen significant advancement in our understanding of the development of biofilms and the processes occurring within these colonies of adhered microorganisms (Coenye & Nelis, 2010; Hall-Stoodley et al., 2004). Two features in particular distinguish microorganisms in biofilms from their free-living counterparts. The first is their ability to produce a coherent extracellular polymeric matrix (containing polysaccharides, proteins and DNA) which results in firmer attachment to the surface (Costerton et al., 1987; Donlan & Costerton, 2002). The other is the coordinated behaviour of the cells embedded in this matrix due to communication by a process known as quorum sensing. Quorum sensing is the secretion and detection of inducer molecules that accumulate as a function of cell density. At a threshold population density the accumulated autoinducers bind to cellular receptors activating transcription of certain genes (Costerton & Lapin-Scott, 1995; Hall-Stoodley et al., 2004; Nadell et al., 2008; Sauer, 2003). While the existence of a biofilm is beneficial in many settings, for example in waste water treatment plants where they play an essential role in flocculation and nutrient removal (Nicolella et al., 2000; Wagner & Loy, 2002), their presence can also be extremely harmful or costly. Biofilms are implicated in numerous diseases, including cystic fibrosis and tuberculosis (Lam et al., 1980; Singh et al., 2000); they also contaminate food, its packaging and the water distribution network thereby posing a serious threat to human health (Flemming, 2002; Kumar & Anand, 1998; LeChavalier et al., 1987). Microorganism colonization and extracellular polymeric substance (EPS) secretion on man-made structures such as heat exchangers and the hulls of ships can result in decreased performance and increased operating costs (Meesters et al., 2003; Schultz et al., 2011). As such, biofilms have become a priority subject in many research areas in recent years. Publications in the fields of biomedicine (Guo et al., 2008; Morton et al., 1998), waste water treatment (Liu & Fang, 2003; Pollard, 2010), ecology (Lubarsky et al., 2010; Yallop et al., 2000), food science (Carpentier &