Antibiofilm Activity of Antarctic Sponge-Associated Bacteria against Pseudomonas aeruginosa and Staphylococcus aureus

Bioprospecting in unusual marine environments provides an innovative approach to
search novel biomolecules with antibiofilm activity. Antarctic sponge-associated bacteria
belonging to Colwellia, Pseudoalteromonas, Shewanella and Winogradskyella genera were evaluated for
their ability to contrast the biofilm formation by Pseudomonas aeruginosa ATCC 27853 and
Staphylococcus aureus ATCC 29213, as model organisms. All strains were able to produce biofilm at
both 4 and 25 °C, with the highest production being for Colwellia, Shewanella and Winogradskyella
strains at 4 °C after 24 h. Antibiofilm activity of cell-free supernatants (CFSs) differed among
strains and on the basis of their incubation temperature (CFSs4°C and CFSs25°C). The major activity
was observed by CFSs4°C against S. aureus and CFSs25°C against P. aeruginosa, without demonstrating
a bactericidal effect on their growth. Furthermore, the antibiofilm activity of crude extracts from
Colwellia sp. GW185, Shewanella sp. CAL606, and Winogradskyella sp. CAL396 was also evaluated
and visualized by confocal laser scanning microscopic images. Results based on the surface-coating
assay and surface tension measurements suggest that CFSs and the crude extracts may act as
biosurfactants inhibiting the first adhesion of P. aeruginosa and S. aureus. The CFSs and the novel
biopolymers may be useful in applicative perspectives for pharmaceutical and environmental
purposes.