“…The α-, β-, and ω-isomers of hydroxy FAs (<C 18 ) have been studied in environmental samples such as sediments [Kawamura andIshiwatari, 1981, 1982;Ratledge and Wilkinson, 1988;Wakeham et al, 2003], marine aerosols [Kawamura, 1995;Tyagi et al, 2015a], and snow [Tyagi et al, 2015b] as tracers of microorganisms such as algae, fungi, bacteria, protozoa, and epicuticular waxes of higher plants. β-Hydroxy FAs from C 10 to C 18 have been used as chemical markers for Gram-negative bacteria (GNB) and their lipopolysaccharides (LPS) in previous studies of indoor aerosols Sebastian et al, 2006], dust [Reynolds et al, 2005;Saraf et al, 1997], and snow [Tyagi et al, 2015b]. Positional isomers of short-chain αand ω-homologues of hydroxy FAs have been used as potential tracers of soil microorganisms (e.g., bacteria, fungi, yeasts, and protozoa) [Ratledge and Wilkinson, 1988], whereas long-chain αand ω-hydroxy FAs (C 16 to C 32 ) are used as a proxy for microalgae and cyanobacteria , sea grasses [Volkman et al, 1999], and plant waxes [Rogge et al, 1993;Simoneit, 1989].…”