, 2006a; Bragonzi et al , 2009; Hoboth et al , 2009; Rau et al ,

, 2006a; Bragonzi et al., 2009; Hoboth et al., 2009; Rau et al., 2010). Thus, the propensity for genetic change appears to be important for the adaptation of P. aeruginosa CP-673451 datasheet isolates for chronic infection. We have previously shown that clinical isolates of P. aeruginosa indeed generate higher morphotypic and phenotypic diversity when grown as biofilms than does the laboratory strain of P. aeruginosa PAO1 (Kirov et al., 2007; data not shown). We now report that variants derived from in vitro grown biofilms have regained hallmarks of acute infection isolates, suggesting a mechanism by which biofilm growth may contribute to acute exacerbations associated with chronic

infection in the CF airway. We compared the dispersal response of a panel of clinical isolates from patients with CF and showed that all strains exhibited cell death and seeding dispersal from biofilms, high morphotypic diversity and the production of superinfective phage during dispersal (Kirov et al., 2007). Pseudomonas aeruginosa strain 18A was selected from that panel of clinical isolates as a representative strain for further study here. The phenotypes tested in this study included metabolic capacity, virulence factor production and colonisation traits. In comparison with strain PAO1, functional diversification was greatest in the dispersal progeny

of the chronic infection CF isolate, strain 18A. For both strains, the development of stable genetic variants was a feature of biofilm dispersal and was not observed in planktonic cultures. JQ1 supplier The diversification in metabolic capacity may play a crucial role in the establishment of chronic, persistent pulmonary infections of P. aeruginosa in patients with CF. For example, the ability of P. aeruginosa to catabolise alanine is known to provide a competitive advantage over other bacterial strains in vivo (Boulette HSP90 et al.,

2009) and could therefore explain why the clinical strain 18A is able to utilise alanine while the laboratory strain PAO1 cannot. Additionally, Hoboth et al. (2009) reported that clinical CF P. aeruginosa isolates that are hypermutators have increased amino acid uptake. These authors further suggested that ornithine metabolism may play a pivotal role in adaptation within the patient’s lungs. Hence, the higher mutation frequency of strain 18A compared to strain PAO1 may be linked to the increased substrate utilisation by the clinical strain and its biofilm variants. The ability to grow on d-alanine, l-alaninamide and l-ornithine was consistently lost in the dispersal population of the clinical isolate strain 18A. This may be a consequence of biofilm development on a glucose medium in contrast to sputum that contains a range of amino acids, including ornithine and alanine (Palmer et al., 2005, 2007).

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