In times of stress or danger, we often lean on each other for support or seek safety in numbers – and it seems bacteria choose to stick together too. Whether on hard surfaces or floating on liquids, single-celled individuals of certain species can collect to form a cohesive structure, or biofilm, binding themselves together with sugars and proteins. Pictured are two different strains of the bacterium Bacillus subtilis, growing as biofilms on the surface of a liquid culture medium. Constrained by the sides of the dishes, the biofilms are deformed by the pressure as they expand, forming small wrinkles and folds visible to the naked eye. Living in a biofilm may help bacteria to survive harsh conditions: the films are less permeable to liquids and gases, providing some protection against antimicrobial agents, and close proximity may facilitate gene transfer between cells, enhancing the potential for genetic diversity.
Written by Emmanuelle Briolat
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