Probiotics are microbial food supplements (e.g. Lactobacillus spp. and Bifidobacteria spp.) that confer positive health benefits to the host. This largely stems from the ability of probiotics to maintain or restore a healthy microflora within the gastrointestinal and urogenital tracts by direct (e.g. lower pH, production of anti-microbials) and indirect mechanisms (e.g. stimulating host immune system).

Currently our lab, in collaboration with Drs Gregor Reid and John McCormick, have been studying a number of probiotic strains of Lactobacillus that produce bioactive biosurfactants (i.e. a complex mixture of proteins, carbohydrates). Some of the interesting bioactive properties of these strains include in vitro and in vivo anti-adhesion and anti-infective activity against pathogenic bacteria (S. aureus). Current efforts are focused on isolating the bioactive components of the biosurfactants and testing their anti-biofilm activity (Figure 1). It is now recognized that the majority of bacteria grow as biofilms (i.e. multicellular communities enclosed by a slimy matrix). When adapting this defensive mode of growth (estimated to be responsible for ~65% of human infections) they are very difficult to eradicate (~100-1000 times more resistant to antibiotics than their free floating or planktonic bacteria).

Figure 1. Fluoresccent Microcopy of a Staphylococcus aureus biofilm.

A S. aureus biofilm generated on a collagen (type I) coated coverslip was stained with DAPI (DNA) and a FM4-64 (vital dye). Digital images were acquired on a Nikon eclipse TE-200 inverted fluorescent microscope using a Photometrics series 300 cooled CCD camera, and deconvolved using softWoRx (v 2.5) software (Applied Precision Inc., Issaquah WA, USA). Both top (upper) and side (lower) views of the volume reconstructed image of the biofilm are shown. The bar represents 10 mm.