School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
Nat Commun. 2020 Dec 10;11(1):6331. doi: 10.1038/s41467-020-20126-y.
In modern societies, biodegradation of hydrophobic pollutants generated by industry is important for environmental and human health. In Gram-negative bacteria, biodegradation depends on facilitated diffusion of the pollutant substrates into the cell, mediated by specialised outer membrane (OM) channels. Here we show, via a combined experimental and computational approach, that the uptake of monoaromatic hydrocarbons such as toluene in Pseudomonas putida F1 (PpF1) occurs via lateral diffusion through FadL channels. Contrary to classical diffusion channels via which polar substrates move directly into the periplasmic space, PpF1 TodX and CymD direct their hydrophobic substrates into the OM via a lateral opening in the channel wall, bypassing the polar barrier formed by the lipopolysaccharide leaflet on the cell surface. Our study suggests that lateral diffusion of hydrophobic molecules is the modus operandi of all FadL channels, with potential implications for diverse areas such as biodegradation, quorum sensing and gut biology.
在现代社会中，工业产生的疏水性污染物的生物降解对于环境和人类健康至关重要。在革兰氏阴性菌中，污染物底物的生物降解取决于通过专门的外膜（OM）通道促进扩散进入细胞。在这里，我们通过结合实验和计算方法表明，在 Pseudomonas putida F1（PpF1）中，单芳烃类化合物如甲苯的摄取是通过 FadL 通道的侧向扩散发生的。与极性底物直接进入周质空间的经典扩散通道相反，PpF1 TodX 和 CymD 通过通道壁上的侧向开口将其疏水性底物引导至 OM，绕过细胞表面脂多糖叶层形成的极性屏障。我们的研究表明，疏水分子的侧向扩散是所有 FadL 通道的作用方式，这可能对生物降解、群体感应和肠道生物学等多个领域产生影响。
