Figure 1.

Schematic representation of the AcrAB-TolC efflux pump (A), and assay developed to determine the impact of 1-hexene on cell survival (B). A: Organization of the three proteins forming the tripartite efflux pump complex and their localization in the E. coli membrane is represented. The trimer of the AcrB subunit is shown in color. The newly discovered AcrZ domain (Hobbs et al., 2012) is not depicted in this diagram. B: Assay with a saturated atmosphere using the volatile compound to impose toxicity. The arrows represent the inoculation cell culture on the agar surface; the open lid of the petri-dish is used to place small receptacles containing a volatile compound. The chamber is assembled by inverting the petri-dish on the lid, cells facing the receptacles and sealed using parafilm (See methods). This method was used for 1-hexene survival assays as well as to screen AcrB mutants. The saturated atmosphere assay was also used with other alpha-olefins like 1-octene and 1-nonene.