Biofilms - Consolidation

BIOFILMS

Cell attachment, and subsequent biofilm formation, is a means by which pathogens can remain in a favourable environment (i.e. one where there are plenty of nutrients) without getting washed away. As a consequence, bacterial cell numbers and activities can become quite high. Biofilms can form on any surface (e.g. soft tissue, bone, medical implants) and may contain only one or two species (e.g. Staph. aureus mediated osteomyelitis) or more commonly several species of bacteria (e.g. dental plaque). Hence, biofilms may be considered as a functional microbial community. Within a biofilm intracellular signalling molecules (e.g. Nacyl homoserine lactones) are produced that when sufficient (threshold) concentrations are reached, upregulate bio-film specific genes. This process is known as quorum sensing, and is responsible for the formation and maintenance of the biofilm.

Once formed, biofilms can be extremely difficult, if not impossible, to remove. Their size and morphology can help protect the underlying cells, resisting physical forces or removal, phagocytosis and penetration of toxic molecules such as antibiotics. In addition, biofilms allow cells to live in close proximity to each other, thereby facilitating intercellular communication and genetic exchange. Finally, due to their profound resistance, biofilms provide foci of infection which often can only be removed by surgery.