Fig. 1

Schematic model of molecular and biochemical impacts of dioxins on lipid biosynthesis and cell membrane composition in soil microorganisms. Due to their extreme lipophilicity, dioxins show a high affinity towards cellular lipids. After their uptake, dioxins can affect the metabolism of microbial FAs by two distinct and mutually exclusive UFA biosynthetic pathways in bacteria, an anaerobic and an aerobic pathway. (1) The first is used by anaerobes and some facultative aerobic microorganisms leading to produce UFAs by de novo synthesis under the action of an FA synthase. (2) The other produces only saturated FAs, via multisubunit associated-membrane desaturases. This generally modifies the composition of cellular FAs leading to decreasing ratios of saturated FAs/unsaturated FAs (SFAs/USFAs), branched-chain FAs/straight chain FAs (BCFAs/SCFAs). It also leads to the generation of an unusual FAs such as branched-chain unsaturated FAs (BCUSFAs), which enhances the fluidity and permeability of the cell membrane. The spectrum of unusual FAs produced as part of dioxin responses in these bacteria gives rise to specific “lipidic signatures” that can be used as part of diagnostic and remediation strategies to address such environmental pollutants