Biofi lm formation by an ancestral strain (NCIB3610) of the commonly used Bacillus subtilis laboratory strain, 168, as monitored by the formation of rugose colonies. The colony surface is highly hydrophobic as evidenced by the beading of a water droplet (7 μl) stained with red food coloring. For further details readers are referred to the MicroReview by Cairns et al . on pp. 587–598 of this issue