Fig. 2: Gut bacteria concentrate diverse PFAS molecules and can export through a TolC-dependent mechanism in E. coli.
From: Human gut bacteria bioaccumulate per- and polyfluoroalkyl substances
a, PFAS bioaccumulation by live, dead (heat inactivated) and lysed (heat inactivated, freeze-thawed and sonicated) B. uniformis, E. coli and O. splanchnicus cultures (OD600 = 3.75) in PBS buffer. Two-sided t-test; P value FDR corrected for number of strains and compounds tested; *adj. P value < 0.05; **adj. P value < 0.01; ***adj. P value < 0.001 and >20% reduction compared with the compound control; n = 3 technical replicates (Supplementary Table 18). b, AcrAB-TolC efflux pump schematic. The resting state of the pump is depicted on the left. The pump changes conformation to export the xenobiotic (right). TolC can work in combination with other pumps41,81,82. c, Bioaccumulation of PFDA and PFNA by wild-type E. coli strains and corresponding efflux and permeability mutants. Efflux mutants E. coli BW25113 ∆tolC and E. coli C43 (DE3) ∆acrAB-tolC showed a ~1.5-fold increase in PFDA and ~5-fold increase in PFNA bioaccumulation. OD600 = 3.75; exposure concentration = 20 µM (PFNA, 9.3 mg l−1; PFDA, 10.3 mg l−1); two-sided t-test; *P value < 0.05; **P value < 0.01 compared with the corresponding wild type; n = 3 technical replicates (Supplementary Table 19). d, PFNA bioaccumulation by B. uniformis at 0.34 nM (160 ng l−1) exposure. Around 37% of PFNA is sequestered from the media into the bacterial pellet. Two-sided t-test (supernatant compared with the compound control; pellet compared with the pellet control); *P value < 0.05; **P value < 0.01; n = 3 biological replicates (Supplementary Tables 20 and 21). e, Capacity of gut bacteria to concentrate PFAS from the media into the bacterial pellet in a growth assay in mGAM or resting assay in PBS at 5 µM PFAS exposure (growth assay: initial OD600 = 0.05, 24-h incubation; resting assay: OD600 = 3.75, 4-h incubation). n = 3 technical replicates (Supplementary Table 22). f, PFAS recovery from the bacterial pellets after 1 h of exposure in PBS (OD600 = 3.75, PFAS mix of 14 compounds each at a concentration of 1 mg l−1). The bars depict the median concentration based on pellet weight; the error bars show standard error; n = 3 technical replicates shown as circles (Supplementary Table 23).
