Biofilms

Biofilms are microbial communities which develop on solid surfaces. This concept it has been introduced in 1978 by W. Costerton. It progressively changed profoundly the scientific approach to microbiology in general, to bacteriology in particular. Today, bacteria cannot longer be viewed as free floating enzyme bags, but have to be studied in the framework of the exciting complexity found within a biofilm.

In fact, recent research reveals that a biofilm is made of a large number so called sessile bacteria specialize through genomic, epigenomic and genetic mechanisms . A biofilm is  thus similar in many aspects to a complex organism: The biofilm grows locally, forms amazing 3-dimensional structures and maintains itself  over extended periods of time. It also “secretes” so called planctonic bacteria, the familiar free floating bacteria aimed at colonizing new available “biofilm friendly” surfaces far away from the biofilm from which they originate.

Biofilms have to be studied in the framework of their intrinsic structural and dynamical complexity.

Evidence is now accumulating showing that each individual strain found within a biofilm caries a genome which is only a fraction of the “supragenome” of a given specie present within the biofilm. Studying  a single strain is thus no more sufficient. Instead, it is necessary to consider a statistically representative sample of strains , typically 10-30, depending of the specie and the desired coverage. This aspect has often been overlooked in the past.

A biofilm is not forming instantaneously, but builds up following several steps each with its  intrinsic kinetics.  In order to gain in-depth knowledge of the dynamics of biofilm formation, it is necessary to follow the process over many time points and for different initial bacterial coverage.

Biofilms can be studied in-depth using imaging techniques such as scanning electron microscopy and fluorescence confocal microscopy, and genomic methods such as massively parallel sequencing. However, such techniques are not practicable for routine and large scale studies. Other techniques, such as  optical density or light scattering measurements and Cristal Violet are not very informative and eventually very cumbersome.

The BioFilm Ring test ®  is a new technique that enables fast and convenient fundamental studies on biofilm formation as well as high-throughput screening of anti-biofilm preventive and curative treatments.

General litterature on biofilms:

www.nature.com/embor200843.pdf