Abstract
Bacterial biofilms are found in various environmental niches and are mostly comprised by two or more bacterial species. One such example, are the mixed species bacterial biofilms found in chronic lung infections of cystic fibrosis (CF) patients, which include the Staphylococcus aureus and Pseudomonas aeruginosa bacterial species. S. aureus is one of the CF lung initial colonizers and is assumed to be abrogated when P. aeruginosa becomes established, eliminating its involvement as the infection evolves. Common models used in research do not mimic the actual progression of the mixed species biofilms thus, in this work we developed an in vitro model, where S. aureus biofilms establish prior to the introduction of P. aeruginosa, simulating a state that is phenotypically more similar to the one found in CF lungs. Overall our results demonstrate that S. aureus is not outcompeted, and that timing of inoculation and bacterial concentration affect the final bacterial ratio and quorum sensing related gene expression during the dual species biofilm development.
Highlights
Biofilms, bacterial communities with a distinct phenotype compared to free-living planktonic cells, are considered to be responsible for most chronic infections
Biofilm growth results in an increased resistance to environmental stresses and an ability to persist within harsh environments (Stoodley et al, 2002). When gaging their surrounding environment bacteria make use of cell–cell communication, known as quorum sensing (QS), a necessary survival skill as biofilm infections are normally composed by several bacterial species, such as the ones found in wound infections, eye infections, and lung infections of cystic fibrosis (CF) patients (Recsei et al, 1986; Lyczak et al, 2002; Burmølle et al, 2006; Bjarnsholt et al, 2010b; Stacy et al, 2016)
P. aeruginosa was inoculated into pre-cultured (5 day old) S. aureus biofilms grown in 20% brain heart infusion medium (BHI) medium, either at room temperature (RT) or 37◦C (Figure 2), at the ratio of 1 P. aeruginosa to 250 S. aureus
Summary
Bacterial communities with a distinct phenotype compared to free-living planktonic cells, are considered to be responsible for most chronic infections. Biofilm growth results in an increased resistance to environmental stresses and an ability to persist within harsh environments (Stoodley et al, 2002) When gaging their surrounding environment bacteria make use of cell–cell communication, known as quorum sensing (QS), a necessary survival skill as biofilm infections are normally composed by several bacterial species, such as the ones found in wound infections, eye infections, and lung infections of cystic fibrosis (CF) patients (Recsei et al, 1986; Lyczak et al, 2002; Burmølle et al, 2006; Bjarnsholt et al, 2010b; Stacy et al, 2016). These signaling systems have been shown to regulate EPS, efflux pumps, attachment, and virulence factors known to be associated with disease and bacterial cohabitation (Bjarnsholt et al, 2010a).
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