These short-chain carbon molecules have also been reported to have inhibitory properties against S. cerevisiae and C. albicans (Bergsson et al., 2001; Kubo et al., 2003). The size of the chain length is clearly an important factor, which was confirmed in studies of the activity of 40 isomers of farnesol, which concluded that subtle changes in the structure of farnesol can have dramatic effects on the activity against C. albicans (Shchepin et al., 2003). At the molecular level, it is likely that these molecules act to influence key transcription factors, leading

to hyphal repression. Both farnesol and dodecanol were shown to affect the cAMP-controlled Ras1-Cdc35 pathway, which is integral to filamentation (Davis-Hanna et al., 2008). Genome analysis of Aspergillus species indicates that JQ1 order cAMP signalling is conserved, thus indicating that these small 10 carbon molecules may play a pivotal role in fungal population control (Lafon et al., 2006). Moreover, recent transcriptional studies to examine the effects of P. MLN8237 manufacturer aeruginosa supernatant on C. albicans biofilm formation demonstrated that 236 genes were differentially

regulated, and interestingly, genes involved in adhesion and biofilm formation were downregulated, in particular YHP1, which encodes a protein known to inhibit biofilm formation (Holcombe et al., 2010). The suppression of other microbial pathogens via the secretion Rutecarpine of small molecules may play a pivotal role in microbial competition. Within the environment of the CF lung, bacteria and fungi

exist within close proximity, and given that bacterial quorum-sensing molecules have been identified directly from sputum samples of CF patients, it is plausible that complex microbial interactions are modulated through small defined chemical messengers to allow different bacteria and cross-kingdom interactions to take place that impact microbial pathogenicity (Singh et al., 2000; Shirtliff et al., 2009). Investigation of P. aeruginosa clinical isolates from CF patients has shown that the genetic diversity of quorum-sensing networks is common, with 19 out of 30 CF patients reported to contain lasR mutants (Smith et al., 2006). This indicates that P. aeruginosa may evolve within the complex microbial environment to allow its coexistence with eukaryotes, which is supported by data from a recent study describing mutual inhibition (Bandara et al., 2010b). Interesting observations from the same group showed that exogenous lipopolysaccharide was able to inhibit and disrupt Candida spp. biofilms in a time- and concentration-dependent manner (Bandara et al., 2010a). Collectively, the data demonstrate that P. aeruginosa has the ability to modulate C. albicans behaviour in a number of ways, and under certain circumstances, it can mutually coexist.