Unique adaptations of a photosynthetic microbe Rhodopseudomonas palustris to the toxicological effects of perfluorooctanoic acid†

Abstract

In this study, we investigate the PFOA removal capabilities of Rhodopseudomonas palustris (R. palustris), a fluoroacetate dehalogenase containing microbe, as a potential candidate for achieving bioremediation. In the 50-day PFOA uptake experiment, R. palustris removed 44 ± 6.34% PFOA after 20 days of incubation, which was then reduced to a final removal of 6.23 ± 12.75%. Results indicate that PFOA was temporarily incorporated into the cell membrane before being partially released into the media after cell lysis. This incorporation might be attributed to the combined effect of the hydrophobic interaction between PFOA and the cell membrane and the reduced electrostatic repulsion from the high ion concentration in the growth medium. The growth of R. palustris during the PFOA uptake experiment was 45-fold slower than their growth without PFOA. This study also completely defines the toxicity range of PFOA for R. palustris through a toxicity assay. Increasing PFOA concentration reduced microbial growth, with complete inhibition observed at around 200 ppm. An accelerated growth phase was followed by a temporary death phase in the first 24 hours in the presence of 12.5–100 ppm PFOA, implying a unique adaptation mechanism to PFOA.