Pseudomonas aeruginosa growth as suspended aggregates in high viscosity environment

Cystic fibrosis (CF) patients produce copious amounts of sputum in their respiratory tract that obstruct their airways. Bacterial pathogens colonise and form suspended aggregates within these thick sputa and cause chronic respiratory infections. These aggregates have long been considered to be a type of biofilm growth. However, while attachment factors such as extracellular biofilm polysaccharides are crucial for surface-associated biofilms,they are not required to develop aggregates. Therefore, suspended aggregates may represent a distinct and under-characterised growth format of bacteria. Based on our results, suspended aggregates promote multi-species microbiota by spatially restricting interspecies competition (opportunistic and common CF pathogens Pseudomonas aeruginosa + Staphylococcus aureus and P. aeruginosa + host epithelial cells). These provide intriguing framework that suggest bacterial suspended aggregate cultures may be a relevant model system relating to CF respiratory infections.